Comparative whole-genome analyses have demonstrated that horizontal gene transfer (HGT) provides a significant contribution to prokaryotic genome innovation. The evolution of specific prokaryotes is therefore tightly linked to the environment in which they live and the communal pool of genes available within that environment. Here we use the term supergenome to describe the set of all genes that a prokaryotic 'individual' can draw on within a particular environmental setting. Conjugative plasmids can be considered particularly successful entities within the communal pool, which have enabled HGT over large taxonomic distances. These plasmids are collections of discrete regions of genes that function as 'backbone modules' to undertake different aspects of overall plasmid maintenance and propagation. Conjugative plasmids often carry suites of 'accessory elements' that contribute adaptive traits to the hosts and, potentially, other resident prokaryotes within specific environmental niches. Insight into the evolution of plasmid modules therefore contributes to our knowledge of gene dissemination and evolution within prokaryotic communities. This communal pool provides the prokaryotes with an important mechanistic framework for obtaining adaptability and functional diversity that alleviates the need for large genomes of specialized 'private genes'.
OBJECTIVE -The risk of type 2 diabetes is suggested to be increased for individuals exposed to stress. We analyzed the association of work stress by high demands, low decision latitude, and job strain (combination of high demands and low decision latitude) with type 2 diabetes. We also studied low sense of coherence (SOC) (a factor for successful coping with stressors) in association with type 2 diabetes. Finally, we investigated the combination of SOC and demands or SOC and decision latitude in association with the disease. RESEARCH DESIGN AND METHODS-This cross-sectional study recruited 4,821 healthy Swedish women (aged 35-56 years) residing in five municipalities in the Stockholm area. An oral glucose tolerance test identified 52 women with type 2 diabetes. Relative risks (RRs) with 95% CIs were estimated in a logistic multiple regression analysis.RESULTS -No association was found between high demands and type 2 diabetes (RR 1.1 [CI 0.5-2.2]). Low decision latitude was associated with type 2 diabetes with a RR of 2.2 (1.0 -4.8). The RR of type 2 diabetes with low SOC was 3.7 (1.2-11.2). The combination of low SOC and low decision latitude was associated with type 2 diabetes with a RR of 2.6 (1.2-5.7). Homeostasis model assessment revealed an association of 4.2 (1.2-15.0) between low SOC and insulin resistance.CONCLUSIONS -This study provided new evidence that stress factors such as low decision latitude at work and low SOC were associated with type 2 diabetes in middle-aged Swedish women. Diabetes Care 26:719 -724, 2003A n activation of the hypothalamopituitary-adrenal (HPA) axis and the central sympathetic system has been proposed to be responsible for the development of endocrine perturbations, leading to obesity and type 2 diabetes. Hence, psychosocial stress causes insulin resistance via psychoendocrine pathways (1,2). In addition, increased levels of stress hormones, e.g., catecholamines and glucocorticoids, may impair insulin secretion (3). The risk is specifically evident in genetically susceptible individuals exposed to perceived environmental psychological stress (2). A job stress model, the psychological demand-decision latitude model, introduced by Karasek and colleagues (4,5), has been developed for measuring the impact of work stress on the risk of illness. The combination of high demands and low decision latitude, referred to as job strain, increases the risk of coronary heart disease (5-7). Another parameter, sense of coherence (SOC), developed by Antonovsky (8), is suggested to be an important factor in successful coping with stressors and also for maintenance of health. A person with low SOC is more likely to deal unsuccessfully with stressors (8,9). However, to our knowledge there is no published study on the significance of work stress or SOC in association with type 2 diabetes. The aim of our study was to examine the association of self-reported high demands, low decision latitude, job strain, and low SOC with type 2 diabetes in middle-aged Swedish women. Furthermore, the combination of SO...
We assessed the microbial diversity and microenvironmental niche characteristics in the didemnid ascidian Lissoclinum patella using 16S rRNA gene sequencing, microsensor and imaging techniques. L. patella harbors three distinct microbial communities spatially separated by few millimeters of tunic tissue: (i) a biofilm on its upper surface exposed to high irradiance and O 2 levels, (ii) a cloacal cavity dominated by the prochlorophyte Prochloron spp. characterized by strong depletion of visible light and a dynamic chemical microenvironment ranging from hyperoxia in light to anoxia in darkness and (iii) a biofilm covering the underside of the animal, where light is depleted of visible wavelengths and enriched in near-infrared radiation (NIR). Variable chlorophyll fluorescence imaging demonstrated photosynthetic activity, and hyperspectral imaging revealed a diversity of photopigments in all microhabitats. Amplicon sequencing revealed the dominance of cyanobacteria in all three layers. Sequences representing the chlorophyll d containing cyanobacterium Acaryochloris marina and anoxygenic phototrophs were abundant on the underside of the ascidian in shallow waters but declined in deeper waters. This depth dependency was supported by a negative correlation between A. marina abundance and collection depth, explained by the increased attenuation of NIR as a function of water depth. The combination of microenvironmental analysis and fine-scale sampling techniques used in this investigation gives valuable first insights into the distribution, abundance and diversity of bacterial communities associated with tropical ascidians. In particular, we show that microenvironments and microbial diversity can vary significantly over scales of a few millimeters in such habitats; which is information easily lost by bulk sampling.
BackgroundBacteria of the genus Sulfobacillus are found worldwide as members of microbial communities that accelerate sulfide mineral dissolution in acid mine drainage environments (AMD), acid-rock drainage environments (ARD), as well as in industrial bioleaching operations. Despite their frequent identification in these environments, their role in biogeochemical cycling is poorly understood.ResultsHere we report draft genomes of five species of the Sulfobacillus genus (AMDSBA1-5) reconstructed by cultivation-independent sequencing of biofilms sampled from the Richmond Mine (Iron Mountain, CA). Three of these species (AMDSBA2, AMDSBA3, and AMDSBA4) have no cultured representatives while AMDSBA1 is a strain of S. benefaciens, and AMDSBA5 a strain of S. thermosulfidooxidans. We analyzed the diversity of energy conservation and central carbon metabolisms for these genomes and previously published Sulfobacillus genomes. Pathways of sulfur oxidation vary considerably across the genus, including the number and type of subunits of putative heterodisulfide reductase complexes likely involved in sulfur oxidation. The number and type of nickel-iron hydrogenase proteins varied across the genus, as does the presence of different central carbon pathways. Only the AMDSBA3 genome encodes a dissimilatory nitrate reducatase and only the AMDSBA5 and S. thermosulfidooxidans genomes encode assimilatory nitrate reductases. Within the genus, AMDSBA4 is unusual in that its electron transport chain includes a cytochrome bc type complex, a unique cytochrome c oxidase, and two distinct succinate dehydrogenase complexes.ConclusionsOverall, the results significantly expand our understanding of carbon, sulfur, nitrogen, and hydrogen metabolism within the Sulfobacillus genus.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-1107) contains supplementary material, which is available to authorized users.
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