Category Archives: Science News

New and Exciting in PLoS Biology and PLoS Medicine

Evolving Towards Mutualism:

Plants, and all other living things, require nitrogen for growth; it is an essential component of nucleic acids and proteins. Although air is mostly nitrogen, this gaseous form is inaccessible to plants and must be fixed into ammonium to render it biologically relevant. Soil bacteria called rhizobia fix nitrogen, but to do this they must first take up residence inside the roots of legumes like pea, alfalfa, clover, and soybean.

Experimental Evolution of a Plant Pathogen into a Legume Symbiont:

Most leguminous plants can form a symbiosis with members of a group of soil bacteria known as rhizobia. On the roots of their hosts, some rhizobia elicit the formation of specialized organs, called nodules, that they colonize intracellularly and within which they fix nitrogen to the benefit of the plant. Rhizobia do not form a homogenous taxon but are phylogenetically dispersed bacteria. How such diversity has emerged is a fascinating, but only partly documented, question. Although horizontal transfer of symbiotic plasmids or groups of genes has played a major role in the spreading of symbiosis, such gene transfer alone is usually unproductive because genetic or ecological barriers restrict evolution of symbiosis. Here, we experimentally evolved the usually phytopathogenic bacterium Ralstonia solanacearum, which was carrying a rhizobial symbiotic plasmid into legume-nodulating and -infecting symbionts. From resequencing the bacterial genomes, we showed that inactivation of a single regulatory gene allowed the transition from pathogenesis to legume symbiosis. Our findings indicate that following the initial transfer of symbiotic genes, subsequent genome adaptation under selection in the plant has been crucial for the evolution and diversification of rhizobia.

The Global Health System: Strengthening National Health Systems as the Next Step for Global Progress:

Three circumstances make the present moment unique for global health. First, health has been increasingly recognized as a key element of sustainable economic development [1], global security, effective governance, and human rights promotion [2]. Second, due to the growing perceived importance of health, unprecedented–albeit still insufficient–sums of funds are flowing into this sector [3]. Third, there is a burst of new initiatives coming forth to strengthen national health systems as the core of the global health system and a fundamental strategy to achieve the health-related Millennium Development Goals.
In order to realize the opportunities offered by the conjunction of these unique circumstances, it is essential to have a clear conception of national health systems that may guide further progress in global health. To that effect, the first part of this Policy Forum examines some common misconceptions about health systems. Part two explains a framework to better understand this complex field. Finally, I offer a list of suggestions on how to improve national health system performance and what role global actors can play.

‘Working the System’–British American Tobacco’s Influence on the European Union Treaty and Its Implications for Policy: An Analysis of Internal Tobacco Industry Documents:

The primary goal of public health, the branch of medicine concerned with the health of communities, is to improve lives by preventing disease. Public-health groups do this by assessing and monitoring the health of communities, by ensuring that populations have access to appropriate and cost-effective health care, and by helping to formulate public policies that safeguard human health. Until recently, most of the world’s major public-health concerns related to infectious diseases. Nowadays, however, many major public-health concerns are linked to the goods made and marketed by large corporations such as fast food, alcohol, tobacco, and chemicals. In Europe, these corporations are regulated by policies drawn up both by member states and by the European Commission, the executive organ of the European Union (EU; an economic and political partnership among 27 democratic European countries). Thus, for example, the tobacco industry, which is widely recognized as a driver of the smoking epidemic, is regulated by Europe-wide tobacco control policies and member state level policies.

3-D articles in PLoS ONE

Two more 3-D articles were published in PLoS ONE today, as a part of our Structural Biology and Human Health: Medically Relevant Proteins from the SGC Collection. Check them out:
Structural Biology of Human H3K9 Methyltransferases:

SET domain methyltransferases deposit methyl marks on specific histone tail lysine residues and play a major role in epigenetic regulation of gene transcription. We solved the structures of the catalytic domains of GLP, G9a, Suv39H2 and PRDM2, four of the eight known human H3K9 methyltransferases in their apo conformation or in complex with the methyl donating cofactor, and peptide substrates. We analyzed the structural determinants for methylation state specificity, and designed a G9a mutant able to tri-methylate H3K9. We show that the I-SET domain acts as a rigid docking platform, while induced-fit of the Post-SET domain is necessary to achieve a catalytically competent conformation. We also propose a model where long-range electrostatics bring enzyme and histone substrate together, while the presence of an arginine upstream of the target lysine is critical for binding and specificity.

Crystal Structures of the ATPase Domains of Four Human Hsp70 Isoforms: HSPA1L/Hsp70-hom, HSPA2/Hsp70-2, HSPA6/Hsp70B’, and HSPA5/BiP/GRP78:

The 70-kDa heat shock proteins (Hsp70) are chaperones with central roles in processes that involve polypeptide remodeling events. Hsp70 proteins consist of two major functional domains: an N-terminal nucleotide binding domain (NBD) with ATPase activity, and a C-terminal substrate binding domain (SBD). We present the first crystal structures of four human Hsp70 isoforms, those of the NBDs of HSPA1L, HSPA2, HSPA5 and HSPA6. As previously with Hsp70 family members, all four proteins crystallized in a closed cleft conformation, although a slight cleft opening through rotation of subdomain IIB was observed for the HSPA5-ADP complex. The structures presented here support the view that the NBDs of human Hsp70 function by conserved mechanisms and contribute little to isoform specificity, which instead is brought about by the SBDs and by accessory proteins.

Along with those, check the other new articles today, including:
Marine Reserves Enhance the Recovery of Corals on Caribbean Reefs:

The fisheries and biodiversity benefits of marine reserves are widely recognised but there is mounting interest in exploiting the importance of herbivorous fishes as a tool to help ecosystems recover from climate change impacts. This approach might be particularly suitable for coral reefs, which are acutely threatened by climate change, yet the trophic cascades generated by reserves are strong enough that they might theoretically enhance the rate of coral recovery after disturbance. However, evidence for reserves facilitating coral recovery has been lacking. Here we investigate whether reductions in macroalgal cover, caused by recovery of herbivorous parrotfishes within a reserve, have resulted in a faster rate of coral recovery than in areas subject to fishing. Surveys of ten sites inside and outside a Bahamian marine reserve over a 2.5-year period demonstrated that increases in coral cover, including adjustments for the initial size-distribution of corals, were significantly higher at reserve sites than those in non-reserve sites. Furthermore, macroalgal cover was significantly negatively correlated with the change in total coral cover over time. Recovery rates of individual species were generally consistent with small-scale manipulations on coral-macroalgal interactions, but also revealed differences that demonstrate the difficulties of translating experiments across spatial scales. Size-frequency data indicated that species which were particularly affected by high abundances of macroalgae outside the reserve had a population bottleneck restricting the supply of smaller corals to larger size classes. Importantly, because coral cover increased from a heavily degraded state, and recovery from such states has not previously been described, similar or better outcomes should be expected for many reefs in the region. Reducing herbivore exploitation as part of an ecosystem-based management strategy for coral reefs appears to be justified.

As always, you should rate the articles, post notes and comments and send trackbacks when you blog about the papers.

New and Exciting in PLoS ONE

There are 20 new articles in PLoS ONE today (and there were 14 yesterday). As always, you should rate the articles, post notes and comments and send trackbacks when you blog about the papers. You can now also easily place articles on various social services (CiteULike, Mendeley, Connotea, Stumbleupon, Facebook and Digg) with just one click. Here are my own picks for the week – you go and look for your own favourites:
Role of the Amygdala in Antidepressant Effects on Hippocampal Cell Proliferation and Survival and on Depression-like Behavior in the Rat:

The stimulation of adult hippocampal neurogenesis by antidepressants has been associated with multiple molecular pathways, but the potential influence exerted by other brain areas has received much less attention. The basolateral complex of the amygdala (BLA), a region involved in anxiety and a site of action of antidepressants, has been implicated in both basal and stress-induced changes in neural plasticity in the dentate gyrus. We investigated here whether the BLA modulates the effects of the SSRI antidepressant fluoxetine on hippocampal cell proliferation and survival in relation to a behavioral index of depression-like behavior (forced swim test). We used a lesion approach targeting the BLA along with a chronic treatment with fluoxetine, and monitored basal anxiety levels given the important role of this behavioral trait in the progress of depression. Chronic fluoxetine treatment had a positive effect on hippocampal cell survival only when the BLA was lesioned. Anxiety was related to hippocampal cell survival in opposite ways in sham- and BLA-lesioned animals (i.e., negatively in sham- and positively in BLA-lesioned animals). Both BLA lesions and low anxiety were critical factors to enable a negative relationship between cell proliferation and depression-like behavior. Therefore, our study highlights a role for the amygdala on fluoxetine-stimulated cell survival and on the establishment of a link between cell proliferation and depression-like behavior. It also reveals an important modulatory role for anxiety on cell proliferation involving both BLA-dependent and -independent mechanisms. Our findings underscore the amygdala as a potential target to modulate antidepressants’ action in hippocampal neurogenesis and in their link to depression-like behaviors.

Phylogenetic Analysis of Cellulolytic Enzyme Genes from Representative Lineages of Termites and a Related Cockroach:

The relationship between xylophagous termites and the protists resident in their hindguts is a textbook example of symbiosis. The essential steps of lignocellulose degradation handled by these protists allow the host termites to thrive on a wood diet. There has never been a comprehensive analysis of lignocellulose degradation by protists, however, as it has proven difficult to establish these symbionts in pure culture. The trends in lignocellulose degradation during the evolution of the host lineage are also largely unknown. To clarify these points without any cultivation technique, we performed meta-expressed sequence tag (EST) analysis of cDNA libraries originating from symbiotic protistan communities in four termite species and a wood-feeding cockroach. Our results reveal the establishment of a degradation system with multiple enzymes at the ancestral stage of termite-protistan symbiosis, especially GHF5 and 7. According to our phylogenetic analyses, the enzymes comprising the protistan lignocellulose degradation system are coded not only by genes innate to the protists, but also genes acquired by the protists via lateral transfer from bacteria. This gives us a fresh perspective from which to understand the evolutionary dynamics of symbiosis.

The Quantitative Genetics of Phenotypic Robustness:

Phenotypic robustness, or canalization, has been extensively investigated both experimentally and theoretically. However, it remains unknown to what extent robustness varies between individuals, and whether factors buffering environmental variation also buffer genetic variation. Here we introduce a quantitative genetic approach to these issues, and apply this approach to data from three species. In mice, we find suggestive evidence that for hundreds of gene expression traits, robustness is polymorphic and can be genetically mapped to discrete genomic loci. Moreover, we find that the polymorphisms buffering genetic variation are distinct from those buffering environmental variation. In fact, these two classes have quite distinct mechanistic bases: environmental buffers of gene expression are predominantly sex-specific and trans-acting, whereas genetic buffers are not sex-specific and often cis-acting. Data from studies of morphological and life-history traits in plants and yeast support the distinction between polymorphisms buffering genetic and environmental variation, and further suggest that loci buffering different types of environmental variation do overlap with one another. These preliminary results suggest that naturally occurring polymorphisms affecting phenotypic robustness could be abundant, and that these polymorphisms may generally buffer either genetic or environmental variation, but not both.

Olfactory Imprinting of Amino Acids in Lacustrine Sockeye Salmon:

Juvenile salmon have an olfactory ability to imprint their natal stream odors, but neither the odor properties of natal stream water nor the imprinting timing and duration have been clarified as yet. Here we show, using electrophysiological and behavioral experiments, that one-year-old lacustrine sockeye salmon (Oncorhynchus nerka) can be imprinted around the stage of parr-smolt transformation (PST) by a single amino acid, 1 µM L-proline (Pro), or L-glutamic acid (Glu). We also show by real-time PCR that changes occur in mRNA levels of the salmon olfactory imprinting-related gene (SOIG) around PST. The electro-olfactogram (EOG) responses of test fish exposed to Pro in March (before PST) and April-June (during PST) for 2 weeks were significantly (1.7-fold) greater than those of non-exposed control fish, but not those of test fish exposed in July (after PST). When Pro and control water were added to the water inlets of a two-choice test tank during the spawning season 2 years after the test water exposure, 80% of maturing and matured test fish exposed before and during PST showed a preference for Pro, whereas those exposed after PST did not. The EOG response of test fish exposed to Pro or Glu for 1 hour, 6 hours, 1 day, 7 days, or 14 days in May revealed that only the response after 14 days of exposure was significantly (1.8-fold) greater than the control. The expression levels of SOIG mRNA increased before and during PST, and decreased after PST. We conclude that one-year-old lacustrine sockeye salmon can be imprinted by a single amino acid before and during PST, and that imprinting requires exposure for at least 14 days.

Genetic Structure Among 50 Species of the Northeastern Pacific Rocky Intertidal Community:

Comparing many species’ population genetic patterns across the same seascape can identify species with different levels of structure, and suggest hypotheses about the processes that cause such variation for species in the same ecosystem. This comparative approach helps focus on geographic barriers and selective or demographic processes that define genetic connectivity on an ecosystem scale, the understanding of which is particularly important for large-scale management efforts. Moreover, a multispecies dataset has great statistical advantages over single-species studies, lending explanatory power in an effort to uncover the mechanisms driving population structure. Here, we analyze a 50-species dataset of Pacific nearshore invertebrates with the aim of discovering the most influential structuring factors along the Pacific coast of North America. We collected cytochrome c oxidase I (COI) mtDNA data from populations of 34 species of marine invertebrates sampled coarsely at four coastal locations in California, Oregon, and Alaska, and added published data from 16 additional species. All nine species with non-pelagic development have strong genetic structure. For the 41 species with pelagic development, 13 show significant genetic differentiation, nine of which show striking FST levels of 0.1-0.6. Finer scale geographic investigations show unexpected regional patterns of genetic change near Cape Mendocino in northern California for five of the six species tested. The region between Oregon and Alaska is a second focus of intraspecific genetic change, showing differentiation in half the species tested. Across regions, strong genetic subdivision occurs more often than expected in mid-to-high intertidal species, a result that may reflect reduced gene flow due to natural selection along coastal environmental gradients. Finally, the results highlight the importance of making primary research accessible to policymakers, as unexpected barriers to marine dispersal break the coast into separate demographic zones that may require their own management plans.

New and Exciting in PLoS ONE

There are 27 new articles in PLoS ONE today. As always, you should rate the articles, post notes and comments and send trackbacks when you blog about the papers. You can now also easily place articles on various social services (CiteULike, Mendeley, Connotea, Stumbleupon, Facebook and Digg) with just one click. Here are my own picks for the week – you go and look for your own favourites:
Global versus Local Conservation Focus of U.S. State Agency Endangered Bird Species Lists:

The development of species priorities for conservation at local or regional scales (for example, within a state or province) poses an interesting paradox. One the one hand, locally or regionally-derived species priorities may lead to greater interest in and resources directed to biodiversity conservation by local or regional institutions. On the other hand, locally or regionally-derived species priorities could overlook national or global priorities. We assessed U.S. state government agency endangered-threatened bird lists to determine the comparative representation of species of global versus local conservation significance on them. State lists tended to be represented primarily by species of low global risk-low global responsibility (range: 15-100%; mean 51%) and high global risk-high global responsibility (range: 0-73%; mean 35%). In 25 states, more than half of the species on the state lists were in the low global risk-low global responsibility category. Most U.S. state agency lists represent a combined strategy of highlighting species of both local and global conservation significance. Even with this combined local-global strategy, most state lists were predominated by species that represent local but not global conservation significance. Such a strategy could have profound negative consequences for many species that are not formally recognized under national endangered species protections but that are also left off of state-level endangered species lists.

Ecoimmunity in Darwin’s Finches: Invasive Parasites Trigger Acquired Immunity in the Medium Ground Finch (Geospiza fortis):

Invasive parasites are a major threat to island populations of animals. Darwin’s finches of the Galápagos Islands are under attack by introduced pox virus (Poxvirus avium) and nest flies (Philornis downsi). We developed assays for parasite-specific antibody responses in Darwin’s finches (Geospiza fortis), to test for relationships between adaptive immune responses to novel parasites and spatial-temporal variation in the occurrence of parasite pressure among G. fortis populations. We developed enzyme-linked immunosorbent assays (ELISAs) for the presence of antibodies in the serum of Darwin’s finches specific to pox virus or Philornis proteins. We compared antibody levels between bird populations with and without evidence of pox infection (visible lesions), and among birds sampled before nesting (prior to nest-fly exposure) versus during nesting (with fly exposure). Birds from the Pox-positive population had higher levels of pox-binding antibodies. Philornis-binding antibody levels were higher in birds sampled during nesting. Female birds, which occupy the nest, had higher Philornis-binding antibody levels than males. The study was limited by an inability to confirm pox exposure independent of obvious lesions. However, the lasting effects of pox infection (e.g., scarring and lost digits) were expected to be reliable indicators of prior pox infection. This is the first demonstration, to our knowledge, of parasite-specific antibody responses to multiple classes of parasites in a wild population of birds. Darwin’s finches initiated acquired immune responses to novel parasites. Our study has vital implications for invasion biology and ecological immunology. The adaptive immune response of Darwin’s finches may help combat the negative effects of parasitism. Alternatively, the physiological cost of mounting such a response could outweigh any benefits, accelerating population decline. Tests of the fitness implications of parasite-specific immune responses in Darwin’s finches are urgently needed.

Song Practice Promotes Acute Vocal Variability at a Key Stage of Sensorimotor Learning:

Trial by trial variability during motor learning is a feature encoded by the basal ganglia of both humans and songbirds, and is important for reinforcement of optimal motor patterns, including those that produce speech and birdsong. Given the many parallels between these behaviors, songbirds provide a useful model to investigate neural mechanisms underlying vocal learning. In juvenile and adult male zebra finches, endogenous levels of FoxP2, a molecule critical for language, decrease two hours after morning song onset within area X, part of the basal ganglia-forebrain pathway dedicated to song. In juveniles, experimental ‘knockdown’ of area X FoxP2 results in abnormally variable song in adulthood. These findings motivated our hypothesis that low FoxP2 levels increase vocal variability, enabling vocal motor exploration in normal birds. After two hours in either singing or non-singing conditions (previously shown to produce differential area X FoxP2 levels), phonological and sequential features of the subsequent songs were compared across conditions in the same bird. In line with our prediction, analysis of songs sung by 75 day (75d) birds revealed that syllable structure was more variable and sequence stereotypy was reduced following two hours of continuous practice compared to these features following two hours of non-singing. Similar trends in song were observed in these birds at 65d, despite higher overall within-condition variability at this age. Together with previous work, these findings point to the importance of behaviorally-driven acute periods during song learning that allow for both refinement and reinforcement of motor patterns. Future work is aimed at testing the observation that not only does vocal practice influence expression of molecular networks, but that these networks then influence subsequent variability in these skills.

Striatal FoxP2 Is Actively Regulated during Songbird Sensorimotor Learning:

Mutations in the FOXP2 transcription factor lead to language disorders with developmental onset. Accompanying structural abnormalities in cortico-striatal circuitry indicate that at least a portion of the behavioral phenotype is due to organizational deficits. We previously found parallel FoxP2 expression patterns in human and songbird cortico/pallio-striatal circuits important for learned vocalizations, suggesting that FoxP2’s function in birdsong may generalize to speech. We used zebra finches to address the question of whether FoxP2 is additionally important in the post-organizational function of these circuits. In both humans and songbirds, vocal learning depends on auditory guidance to achieve and maintain optimal vocal output. We tested whether deafening prior to or during the sensorimotor phase of song learning disrupted FoxP2 expression in song circuitry. As expected, the songs of deafened juveniles were abnormal, however basal FoxP2 levels were unaffected. In contrast, when hearing or deaf juveniles sang for two hours in the morning, FoxP2 was acutely down-regulated in the striatal song nucleus, area X. The extent of down-regulation was similar between hearing and deaf birds. Interestingly, levels of FoxP2 and singing were correlated only in hearing birds. Hearing appears to link FoxP2 levels to the amount of vocal practice. As juvenile birds spent more time practicing than did adults, their FoxP2 levels are likely to be low more often. Behaviorally-driven reductions in the mRNA encoding this transcription factor could ultimately affect downstream molecules that function in vocal exploration, especially during sensorimotor learning.

The Effects of Circumcision on the Penis Microbiome:

Circumcision is associated with significant reductions in HIV, HSV-2 and HPV infections among men and significant reductions in bacterial vaginosis among their female partners. We assessed the penile (coronal sulci) microbiota in 12 HIV-negative Ugandan men before and after circumcision. Microbiota were characterized using sequence-tagged 16S rRNA gene pyrosequencing targeting the V3-V4 hypervariable regions. Taxonomic classification was performed using the RDP Naïve Bayesian Classifier. Among the 42 unique bacterial families identified, Pseudomonadaceae and Oxalobactericeae were the most abundant irrespective of circumcision status. Circumcision was associated with a significant change in the overall microbiota (PerMANOVA p = 0.007) and with a significant decrease in putative anaerobic bacterial families (Wilcoxon Signed-Rank test p = 0.014). Specifically, two families–Clostridiales Family XI (p = 0.006) and Prevotellaceae (p = 0.006)–were uniquely abundant before circumcision. Within these families we identified a number of anaerobic genera previously associated with bacterial vaginosis including: Anaerococcus spp., Finegoldia spp., Peptoniphilus spp., and Prevotella spp. The anoxic microenvironment of the subpreputial space may support pro-inflammatory anaerobes that can activate Langerhans cells to present HIV to CD4 cells in draining lymph nodes. Thus, the reduction in putative anaerobic bacteria after circumcision may play a role in protection from HIV and other sexually transmitted diseases.

Biochemical Warfare on the Reef: The Role of Glutathione Transferases in Consumer Tolerance of Dietary Prostaglandins:

Despite the profound variation among marine consumers in tolerance for allelochemically-rich foods, few studies have examined the biochemical adaptations underlying diet choice. Here we examine the role of glutathione S-transferases (GSTs) in the detoxification of dietary allelochemicals in the digestive gland of the predatory gastropod Cyphoma gibbosum, a generalist consumer of gorgonian corals. Controlled laboratory feeding experiments were used to investigate the influence of gorgonian diet on Cyphoma GST activity and isoform expression. Gorgonian extracts and semi-purified fractions were also screened to identify inhibitors and possible substrates of Cyphoma GSTs. In addition, we investigated the inhibitory properties of prostaglandins (PGs) structurally similar to antipredatory PGs found in high concentrations in the Caribbean gorgonian Plexaura homomalla. Cyphoma GST subunit composition was invariant and activity was constitutively high regardless of gorgonian diet. Bioassay-guided fractionation of gorgonian extracts revealed that moderately hydrophobic fractions from all eight gorgonian species examined contained putative GST substrates/inhibitors. LC-MS and NMR spectral analysis of the most inhibitory fraction from P. homomalla subsequently identified prostaglandin A2 (PGA2) as the dominant component. A similar screening of commercially available prostaglandins in series A, E, and F revealed that those prostaglandins most abundant in gorgonian tissues (e.g., PGA2) were also the most potent inhibitors. In vivo estimates of PGA2 concentration in digestive gland tissues calculated from snail grazing rates revealed that Cyphoma GSTs would be saturated with respect to PGA2 and operating at or near physiological capacity. The high, constitutive activity of Cyphoma GSTs is likely necessitated by the ubiquitous presence of GST substrates and/or inhibitors in this consumer’s gorgonian diet. This generalist’s GSTs may operate as ‘all-purpose’ detoxification enzymes, capable of conjugating or sequestering a broad range of lipophilic gorgonian compounds, thereby allowing this predator to exploit a range of chemically-defended prey, resulting in a competitive dietary advantage for this species.

Rapid Decline of a Grassland System and Its Ecological and Conservation Implications:

One of the most important conservation issues in ecology is the imperiled state of grassland ecosystems worldwide due to land conversion, desertification, and the loss of native populations and species. The Janos region of northwestern Mexico maintains one of the largest remaining black-tailed prairie dog (Cynomys ludovicianus) colony complexes in North America and supports a high diversity of threatened and endangered species. Yet, cattle grazing, agriculture, and drought have greatly impacted the region. We evaluated the impact of human activities on the Janos grasslands, comparing changes in the vertebrate community over the last two decades. Our results reveal profound, rapid changes in the Janos grassland community, demonstrating large declines in vertebrate abundance across all taxonomic groups. We also found that the 55,000 ha prairie dog colony complex has declined by 73% since 1988. The prairie dog complex has become increasingly fragmented, and their densities have shown a precipitous decline over the years, from an average density of 25 per ha in 1988 to 2 per ha in 2004. We demonstrated that prairie dogs strongly suppressed woody plant encroachment as well as created open grassland habitat by clearing woody vegetation, and found rapid invasion of shrubland once the prairie dogs disappeared from the grasslands. Comparison of grasslands and shrublands showed markedly different species compositions, with species richness being greatest when both habitats were considered together. Our data demonstrate the rapid decline of a grassland ecosystem, and documents the dramatic loss in biodiversity over a very short time period concomitant with anthropogenic grassland degradation and the decline of a keystone species.

The First Bite– Profiling the Predatosome in the Bacterial Pathogen Bdellovibrio:

Bdellovibrio bacteriovorus is a Gram-negative bacterium that is a pathogen of other Gram-negative bacteria, including many bacteria which are pathogens of humans, animals and plants. As such Bdellovibrio has potential as a biocontrol agent, or living antibiotic. B. bacteriovorus HD100 has a large genome and it is not yet known which of it encodes the molecular machinery and genetic control of predatory processes. We have tried to fill this knowledge-gap using mixtures of predator and prey mRNAs to monitor changes in Bdellovibrio gene expression at a timepoint of early-stage prey infection and prey killing in comparison to control cultures of predator and prey alone and also in comparison to Bdellovibrio growing axenically (in a prey-or host independent “HI” manner) on artificial media containing peptone and tryptone. From this we have highlighted genes of the early predatosome with predicted roles in prey killing and digestion and have gained insights into possible regulatory mechanisms as Bdellovibrio enter and establish within the prey bdelloplast. Approximately seven percent of all Bdellovibrio genes were significantly up-regulated at 30 minutes of infection- but not in HI growth- implicating the role of these genes in prey digestion. Five percent were down-regulated significantly, implicating their role in free-swimming, attack-phase physiology. This study gives the first post- genomic insight into the predatory process and reveals some of the important genes that Bdellovibrio expresses inside the prey bacterium during the initial attack.

Antagonistic Parent-Offspring Co-Adaptation:

In species across taxa, offspring have means to influence parental investment (PI). PI thus evolves as an interacting phenotype and indirect genetic effects may strongly affect the co-evolutionary dynamics of offspring and parental behaviors. Evolutionary theory focused on explaining how exaggerated offspring solicitation can be understood as resolution of parent-offspring conflict, but the evolutionary origin and diversification of different forms of family interactions remains unclear. In contrast to previous theory that largely uses a static approach to predict how “offspring individuals” and “parental individuals” should interact given conflict over PI, we present a dynamic theoretical framework of antagonistic selection on the PI individuals obtain/take as offspring and the PI they provide as parents to maximize individual lifetime reproductive success; we analyze a deterministic and a stochastic version of this dynamic framework. We show that a zone for equivalent co-adaptation outcomes exists in which stable levels of PI can evolve and be maintained despite fast strategy transitions and ongoing co-evolutionary dynamics. Under antagonistic co-adaptation, cost-free solicitation can evolve as an adaptation to emerging preferences in parents. We show that antagonistic selection across the offspring and parental life-stage of individuals favors co-adapted offspring and parental behavior within a zone of equivalent outcomes. This antagonistic parent-offspring co-adaptation does not require solicitation to be costly, allows for rapid divergence and evolutionary novelty and potentially explains the origin and diversification of the observed provisioning forms in family life.

Fish as Reservoirs and Vectors of Vibrio cholerae:

Vibrio cholerae, the etiologic agent of cholera, is autochthonous to various aquatic environments, but despite intensive efforts its ecology remains an enigma. Recently, it was suggested that copepods and chironomids, both considered as natural reservoirs of V. cholerae, are dispersed by migratory waterbirds, thus possibly distributing the bacteria between water bodies within and between continents. Although fish have been implicated in the scientific literature with cholera cases, as far as we know, no study actually surveyed the presence of the bacteria in the fish. Here we show for the first time that fish of various species and habitats contain V. cholerae in their digestive tract. Fish (n = 110) were randomly sampled from freshwater and marine habitats in Israel. Ten different fish species sampled from freshwater habitats (lake, rivers and fish ponds), and one marine species, were found to carry V. cholerae. The fish intestine of Sarotherodon galilaeus harboured ca. 5×103 V. cholerae cfu per 1 gr intestine content–high rates compared with known V. cholerae cfu numbers in the bacteria’s natural reservoirs. Our results, combined with evidence from the literature, suggest that fish are reservoirs of V. cholerae. As fish carrying the bacteria swim from one location to another (some fish species move from rivers to lakes or sea and vice versa), they serve as vectors on a small scale. Nevertheless, fish are consumed by waterbirds, which disseminate the bacteria on a global scale. Moreover, V. cholerae isolates had the ability to degrade chitin, indicating a commensal relationship between V. cholerae and fish. Better understanding of V. cholerae ecology can help reduce the times that human beings come into contact with this pathogen and thus minimize the health risk this poses.

New and Exciting in PLoS this week

Picks from PLoS Biology, PLoS Medicine, PLoS Neglected Tropical Diseases and PLoS ONE:
Preserving a Space for Science in an Age of Democracy:

How should scientific advice be incorporated into the political decisionmaking process? Even experts can’t keep up with the torrent of studies published in their own field, and, supposedly, scientific issues–from climate change to biodiversity loss–have obvious political components. How is advice treated in an age when experts are increasingly viewed with suspicion and distrust?
The Paradox of Scientific Authority: The Role of Scientific Advice in Democracies, by Wiebe E Bijker, Roland Bal, and Ruud Hendriks, reveals the political decision-making in a study of the inner workings of the “Gezondheidsraad,” a scientific advisory body to the Dutch government. Dutch officials invited Bijker et al. to observe the process and write their account, which was eventually presented to Queen Beatrix. So, it is one of those instances–these days growing in number–where the once-reviled sociologists are being asked to help the powerful understand the relationship between policy and science. The authors are well aware of the problems posed for their objectivity–both actual and perceived–by this dangerous shift from outsider to insider.

The Global Health System: Actors, Norms, and Expectations in Transition:

The global health system that evolved through the latter half of the 20th century achieved extraordinary success in controlling infectious diseases and reducing child mortality. Life expectancy in low- and middle-income countries increased at a rate of about 5 years every decade for the past 40 years [1]. Today, however, that system is in a state of profound transition. The need has rarely been greater to rethink how we endeavor to meet global health needs.
We present here a series of four papers on one dimension of the global health transition: its changing institutional arrangements. We define institutional arrangements broadly to include both the actors (individuals and/or organizations) that exert influence in global health and the norms and expectations that govern the relationships among them (see Box 1 for definitions of the terms used in this article).

Syphilis at the Crossroad of Phylogenetics and Paleopathology:

Syphilis is a reemerging disease burden. Although it has been studied for five centuries, its origin and spread is still controversial. Did it accompany the evolution of the genus Homo and does it date back to more than a million years or did it emerge only after Columbus’s return to Europe? Initially, to test the validity of a new interdisciplinary approach we constructed a worldwide map showing precolumbian human skeletons with lesions of syphilis and other related diseases (also caused by different treponemes). Then, we selected the oldest cases to estimate the timing of the treponemes’ history, using their DNA sequences and computer simulations. This resulted in treponeme evolutionary rates, and in temporal intervals during which these microorganisms could have emerged. Based on comparisons with other bacteria, we concluded that treponematoses did not emerge before our own species originated and that syphilis did not start affecting mankind only from 1492 onwards. Instead, it seems to have emerged in the time span between 16,500 and 5,000 years ago. Where syphilis emerged, however, remains unsolved. Finally, the endeavor of joining as distinct fields as paleopathology and molecular biology proved to be fruitful and promising to advance our understanding of the rise and fall of the infectious diseases that have afflicted humans across time and space.

Dissemination of Spotted Fever Rickettsia Agents in Europe by Migrating Birds:

Migratory birds are known to play a role as long-distance vectors for many microorganisms. To investigate whether this is true of rickettsial agents as well, we characterized tick infestation and gathered ticks from 13,260 migratory passerine birds in Sweden. A total of 1127 Ixodes spp. ticks were removed from these birds and the extracted DNA from 957 of them was available for analyses. The DNA was assayed for detection of Rickettsia spp. using real-time PCR, followed by DNA sequencing for species identification. Rickettsia spp. organisms were detected in 108 (11.3%) of the ticks. Rickettsia helvetica, a spotted fever rickettsia associated with human infections, was predominant among the PCR-positive samples. In 9 (0.8%) of the ticks, the partial sequences of 17kDa and ompB genes showed the greatest similarity to Rickettsia monacensis, an etiologic agent of Mediterranean spotted fever-like illness, previously described in southern Europe as well as to the Rickettsia sp.IrITA3 strain. For 15 (1.4%) of the ticks, the 17kDa, ompB, gltA and ompA genes showed the greatest similarity to Rickettsia sp. strain Davousti, Rickettsia japonica and Rickettsia heilongjiangensis, all closely phylogenetically related, the former previously found in Amblyomma tholloni ticks in Africa and previously not detected in Ixodes spp. ticks. The infestation prevalence of ticks infected with rickettsial organisms was four times higher among ground foraging birds than among other bird species, but the two groups were equally competent in transmitting Rickettsia species. The birds did not seem to serve as reservoir hosts for Rickettsia spp., but in one case it seems likely that the bird was rickettsiemic and that the ticks had acquired the bacteria from the blood of the bird. In conclusion, migratory passerine birds host epidemiologically important vector ticks and Rickettsia species and contribute to the geographic distribution of spotted fever rickettsial agents and their diseases.

Quiet and Poised: ‘Silent’ Genes Accumulate Transcription Machinery:

Gene activation–the process of waking up a silent gene and transcribing its DNA–requires many coordinated processes: the gene must be exposed to transcription factors, which must then pile onto specialized sequences adjacent to the gene-called enhancer and promoter regions, which then attract RNA polymerase (the enzyme that catalyzes the synthesis of messenger RNA), which can then attach and prepare to read the gene’s sequence.
Within the nucleus, each chromosome sits in its own well-defined domain, called its territory. It has long been observed that activated genes relocate outside their chromosome’s territory during expression, leading to the idea that this movement promotes activation by exposing the gene to the transcription machinery.
But is the opposite true? Do genes that remain in their territories have less access to RNA polymerase? It had been thought so, but a new study by Carmelo Ferrai, Sheila Xie, Ana Pombo, Massimo P. Crippa, and colleagues shows that even while sitting quietly within their home turf, some genes are already primed with the transcriptional machinery, poised and ready to go.

Are Patents Impeding Medical Care and Innovation?:

Background to the debate: Pharmaceutical and medical device manufacturers argue that the current patent system is crucial for stimulating research and development (R&D), leading to new products that improve medical care. The financial return on their investments that is afforded by patent protection, they claim, is an incentive toward innovation and reinvestment into further R&D. But this view has been challenged in recent years. Many commentators argue that patents are stifling biomedical research, for example by preventing researchers from accessing patented materials or methods they need for their studies. Patents have also been blamed for impeding medical care by raising prices of essential medicines, such as antiretroviral drugs, in poor countries. This debate examines whether and how patents are impeding health care and innovation.

A Strategy for the Proliferation of Ulva prolifera, Main Causative Species of Green Tides, with Formation of Sporangia by Fragmentation:

Ulva prolifera, a common green seaweed, is one of the causative species of green tides that occurred frequently along the shores of Qingdao in 2008 and had detrimental effects on the preparations for the 2008 Beijing Olympic Games sailing competition, since more than 30 percent of the area of the games was invaded. In view of the rapid accumulation of the vast biomass of floating U. prolifera in green tides, we investigated the formation of sporangia in disks of different diameters excised from U. prolifera, changes of the photosynthetic properties of cells during sporangia formation, and development of spores. The results suggested that disks less than 1.00 mm in diameter were optimal for the formation of sporangia, but there was a small amount of spore release in these. The highest percentage of area of spore release occurred in disks that were 2.50 mm in diameter. In contrast, sporangia were formed only at the cut edges of larger disks (3.00 mm, 3.50 mm, and 4.00 mm in diameter). Additionally, the majority of spores liberated from the disks appeared vigorous and developed successfully into new individuals. These results implied that fragments of the appropriate size from the U. prolifera thalli broken by a variety of factors via producing spores gave rise to the rapid proliferation of the seaweed under field conditions, which may be one of the most important factors to the rapid accumulation of the vast biomass of U. prolifera in the green tide that occurred in Qingdao, 2008.

Relationship between Vehicle Emissions Laws and Incidence of Suicide by Motor Vehicle Exhaust Gas in Australia, 2001-06: An Ecological Analysis:

Suicide (self-inflicted death) is a major, preventable public-health problem. About 1 million people die each year from suicide and about 20 times as many people attempt suicide. Globally, suicide rates have increased by nearly a half over the past 45 years and suicide is now among the three leading causes of death in people aged 15-44 years. Within this age group, 1 in 20 deaths is a suicide. Most people who commit suicide have a mental illness, usually depression or substance abuse, but suicide can also be triggered by a stressful event such as losing a partner. Often warning signs are present–a person who talks about killing themselves must always be taken seriously. Adequate prevention and treatment of mental illness and interventions that teach young people coping skills and improve their self-esteem have shown promise in reducing suicide rates, as have strategies (for example, restrictions on the sale of pain killers) that reduce access to common methods of suicide.

Three Circadian Articles in PLoS ONE today

That is, among 20 new articles in PLoS ONE today. As always, you should rate the articles, post notes and comments and send trackbacks when you blog about the papers. You can now also easily place articles on various social services (CiteULike, Mendeley, Connotea, Stumbleupon, Facebook and Digg) with just one click. Here are my own picks for the week – you go and look for your own favourites:
Distinct Functions of Period2 and Period3 in the Mouse Circadian System Revealed by In Vitro Analysis:

The mammalian circadian system, which is composed of a master pacemaker in the suprachiasmatic nuclei (SCN) as well as other oscillators in the brain and peripheral tissues, controls daily rhythms of behavior and physiology. Lesions of the SCN abolish circadian rhythms of locomotor activity and transplants of fetal SCN tissue restore rhythmic behavior with the periodicity of the donor’s genotype, suggesting that the SCN determines the period of the circadian behavioral rhythm. According to the model of timekeeping in the SCN, the Period (Per) genes are important elements of the transcriptional/translational feedback loops that generate the endogenous circadian rhythm. Previous studies have investigated the functions of the Per genes by examining locomotor activity in mice lacking functional PERIOD proteins. Variable behavioral phenotypes were observed depending on the line and genetic background of the mice. In the current study we assessed both wheel-running activity and Per1-promoter-driven luciferase expression (Per1-luc) in cultured SCN, pituitary, and lung explants from Per2−/− and Per3−/− mice congenic with the C57BL/6J strain. We found that the Per2−/− phenotype is enhanced in vitro compared to in vivo, such that the period of Per1-luc expression in Per2−/− SCN explants is 1.5 hours shorter than in Per2+/+ SCN, while the free-running period of wheel-running activity is only 11 minutes shorter in Per2−/− compared to Per2+/+ mice. In contrast, circadian rhythms in SCN explants from Per3−/− mice do not differ from Per3+/+ mice. Instead, the period and phase of Per1-luc expression are significantly altered in Per3−/− pituitary and lung explants compared to Per3+/+ mice. Taken together these data suggest that the function of each Per gene may differ between tissues. Per2 appears to be important for period determination in the SCN, while Per3 participates in timekeeping in the pituitary and lung.

Sleep Deprivation Influences Diurnal Variation of Human Time Perception with Prefrontal Activity Change: A Functional Near-Infrared Spectroscopy Study:

Human short-time perception shows diurnal variation. In general, short-time perception fluctuates in parallel with circadian clock parameters, while diurnal variation seems to be modulated by sleep deprivation per se. Functional imaging studies have reported that short-time perception recruits a neural network that includes subcortical structures, as well as cortical areas involving the prefrontal cortex (PFC). It has also been reported that the PFC is vulnerable to sleep deprivation, which has an influence on various cognitive functions. The present study is aimed at elucidating the influence of PFC vulnerability to sleep deprivation on short-time perception, using the optical imaging technique of functional near-infrared spectroscopy. Eighteen participants performed 10-s time production tasks before (at 21:00) and after (at 09:00) experimental nights both in sleep-controlled and sleep-deprived conditions in a 4-day laboratory-based crossover study. Compared to the sleep-controlled condition, one-night sleep deprivation induced a significant reduction in the produced time simultaneous with an increased hemodynamic response in the left PFC at 09:00. These results suggest that activation of the left PFC, which possibly reflects functional compensation under a sleep-deprived condition, is associated with alteration of short-time perception.

Regulation of BMAL1 Protein Stability and Circadian Function by GSK3β-Mediated Phosphorylation:

Circadian rhythms govern a large array of physiological and metabolic functions. To achieve plasticity in circadian regulation, proteins constituting the molecular clock machinery undergo various post-translational modifications (PTMs), which influence their activity and intracellular localization. The core clock protein BMAL1 undergoes several PTMs. Here we report that the Akt-GSK3β signaling pathway regulates BMAL1 protein stability and activity. GSK3β phosphorylates BMAL1 specifically on Ser 17 and Thr 21 and primes it for ubiquitylation. In the absence of GSK3β-mediated phosphorylation, BMAL1 becomes stabilized and BMAL1 dependent circadian gene expression is dampened. Dopamine D2 receptor mediated signaling, known to control the Akt-GSK3β pathway, influences BMAL1 stability and in vivo circadian gene expression in striatal neurons. These findings uncover a previously unknown mechanism of circadian clock control. The GSK3β kinase phosphorylates BMAL1, an event that controls the stability of the protein and the amplitude of circadian oscillation. BMAL1 phosphorylation appears to be an important regulatory step in maintaining the robustness of the circadian clock.

New and Exciting in PLoS ONE

There are 19 new articles in PLoS ONE today. As always, you should rate the articles, post notes and comments and send trackbacks when you blog about the papers. You can now also easily place articles on various social services (CiteULike, Mendeley, Connotea, Stumbleupon, Facebook and Digg) with just one click. Here are my own picks for the week – you go and look for your own favourites:
Explaining the Imperfection of the Molecular Clock of Hominid Mitochondria:

The molecular clock of mitochondrial DNA has been extensively used to date various genetic events. However, its substitution rate among humans appears to be higher than rates inferred from human-chimpanzee comparisons, limiting the potential of interspecies clock calibrations for intraspecific dating. It is not well understood how and why the substitution rate accelerates. We have analyzed a phylogenetic tree of 3057 publicly available human mitochondrial DNA coding region sequences for changes in the ratios of mutations belonging to different functional classes. The proportion of non-synonymous and RNA genes substitutions has reduced over hundreds of thousands of years. The highest mutation ratios corresponding to fast acceleration in the apparent substitution rate of the coding sequence have occurred after the end of the Last Ice Age. We recalibrate the molecular clock of human mtDNA as 7990 years per synonymous mutation over the mitochondrial genome. However, the distribution of substitutions at synonymous sites in human data significantly departs from a model assuming a single rate parameter and implies at least 3 different subclasses of sites. Neutral model with 3 synonymous substitution rates can explain most, if not all, of the apparent molecular clock difference between the intra- and interspecies levels. Our findings imply the sluggishness of purifying selection in removing the slightly deleterious mutations from the human as well as the Neandertal and chimpanzee populations. However, for humans, the weakness of purifying selection has been further exacerbated by the population expansions associated with the out-of Africa migration and the end of the Last Ice Age.

Reverse Evolution: Driving Forces Behind the Loss of Acquired Photosynthetic Traits:

The loss of photosynthesis has occurred often in eukaryotic evolution, even more than its acquisition, which occurred at least nine times independently and which generated the evolution of the supergroups Archaeplastida, Rhizaria, Chromalveolata and Excavata. This secondary loss of autotrophic capability is essential to explain the evolution of eukaryotes and the high diversity of protists, which has been severely underestimated until recently. However, the ecological and evolutionary scenarios behind this evolutionary “step back” are still largely unknown. Using a dynamic model of heterotrophic and mixotrophic flagellates and two types of prey, large bacteria and ultramicrobacteria, we examine the influence of DOC concentration, mixotroph’s photosynthetic growth rate, and external limitations of photosynthesis on the coexistence of both types of flagellates. Our key premises are: large bacteria grow faster than small ones at high DOC concentrations, and vice versa; and heterotrophic flagellates are more efficient than the mixotrophs grazing small bacteria (both empirically supported). We show that differential efficiency in bacteria grazing, which strongly depends on cell size, is a key factor to explain the loss of photosynthesis in mixotrophs (which combine photosynthesis and bacterivory) leading to purely heterotrophic lineages. Further, we show in what conditions an heterotroph mutant can coexist, or even out-compete, its mixotrophic ancestor, suggesting that bacterivory and cell size reduction may have been major triggers for the diversification of eukaryotes. Our results suggest that, provided the mixotroph’s photosynthetic advantage is not too large, the (small) heterotroph will also dominate in nutrient-poor environments and will readily invade a community of mixotrophs and bacteria, due to its higher efficiency exploiting the ultramicrobacteria. As carbon-limited conditions were presumably widespread throughout Earth history, such a scenario may explain the numerous transitions from phototrophy to mixotrophy and further to heterotrophy within virtually all major algal lineages. We challenge prevailing concepts that affiliated the evolution of phagotrophy with eutrophic or strongly light-limited environments only.

Improving the Clinical Diagnosis of Influenza–a Comparative Analysis of New Influenza A (H1N1) Cases:

The presentation of new influenza A(H1N1) is broad and evolving as it continues to affect different geographic locations and populations. To improve the accuracy of predicting influenza infection in an outpatient setting, we undertook a comparative analysis of H1N1(2009), seasonal influenza, and persons with acute respiratory illness (ARI) in an outpatient setting. Comparative analyses of one hundred non-matched cases each of PCR confirmed H1N1(2009), seasonal influenza, and ARI cases. Multivariate analysis was performed to look for predictors of influenza infection. Receiver operating characteristic curves were constructed for various combinations of clinical and laboratory case definitions. The initial clinical and laboratory features of H1N1(2009) and seasonal influenza were similar. Among ARI cases, fever, cough, headache, rhinorrhea, the absence of leukocytosis, and a normal chest radiograph positively predict for both PCR-confirmed H1N1-2009 and seasonal influenza infection. The sensitivity and specificity of current WHO and CDC influenza-like illness (ILI) criteria were modest in predicting influenza infection. However, the combination of WHO ILI criteria with the absence of leukocytosis greatly improved the accuracy of diagnosing H1N1(2009) and seasonal influenza (positive LR of 7.8 (95%CI 3.5-17.5) and 9.2 (95%CI 4.1-20.3) respectively). The clinical presentation of H1N1(2009) infection is largely indistinguishable from that of seasonal influenza. Among patients with acute respiratory illness, features such as a temperature greater than 38°C, rhinorrhea, a normal chest radiograph, and the absence of leukocytosis or significant gastrointestinal symptoms were all positively associated with H1N1(2009) and seasonal influenza infection. An enhanced ILI criteria that combines both a symptom complex with the absence of leukocytosis on testing can improve the accuracy of predicting both seasonal and H1N1-2009 influenza infection.