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Metabolite concentrations shape cellular physiology and disease susceptibility, yet the general principles governing metabolome evolution are largely unknown. Here we introduce a measure of conservation of individual metabolite concentrations among related species. By analysing multispecies metabolome datasets in mammals and fruit flies, we show that conservation varies extensively across metabolites. Three major functional properties, metabolite abundance, essentiality and association with human diseases predict conservation, highlighting a striking parallel between the evolutionary forces driving metabolome and protein sequence conservation. Metabolic network simulations recapitulated these general patterns, and revealed that abundant metabolites are highly conserved due to their strong coupling to key metabolic fluxes in the network. This study uncovers simple rules governing metabolic evolution in animals and implies that most metabolome differences between species are permitted, rather than favored by selection. More broadly, our work paves the way towards using evolutionary information to discover biomarkers, as well as to detect pathogenic metabolome alterations in individual patients.

Metabolism is fundamentally intertwined with the ageing process. We here report that a key determinant of cellular lifespan is not only nutrient supply and intracellular metabolism, but also metabolite exchange interactions that occur between cells. Studying chronological ageing in yeast, we observed that metabolites exported by young, exponentially growing, cells are re- imported during the stationary phase when cells age chronologically, indicating the existence of cross-generational metabolic interactions. We then used self-establishing metabolically cooperating communities (SeMeCos) to boost cell-cell metabolic interactions and observed a significant lifespan extension. A search for the underlying mechanisms, coupling SeMeCos, metabolic profiling, proteomics and genome-scale metabolic modelling, attributed a specific role to methionine consumer cells. These cells were enriched over time, adopted glycolytic metabolism and increased export of protective metabolites. Glycerol, in particular, accumulated in the communal metabolic environment and extended the lifespan of all cells in the community in a paracrine fashion. Our results hence establish metabolite exchange interactions as a determinant of the ageing process and show that metabolically cooperating cells shape their metabolic environment to achieve lifespan extension.

Metabolism is deeply intertwined with aging. Effects of metabolic interventions on aging have been explained with intracellular metabolism, growth control, and signaling. Studying chronological aging in yeast, we reveal a so far overlooked metabolic property that influences aging via the exchange of metabolites. We observed that metabolites exported by young cells are re-imported by chronologically aging cells, resulting in cross-generational metabolic interactions. Then, we used self-establishing metabolically cooperating communities (SeMeCo) as a tool to increase metabolite exchange and observed significant lifespan extensions. The longevity of the SeMeCo was attributable to metabolic reconfigurations in methionine consumer cells. These obtained a more glycolytic metabolism and increased the export of protective metabolites that in turn extended the lifespan of cells that supplied them with methionine. Our results establish metabolite exchange interactions as a determinant of cellular aging and show that metabolically cooperating cells can shape the metabolic environment to extend their lifespan.

The formation of Pseudomonas aeruginosa biofilms in cystic fibrosis (CF) is one of the most common causes of morbidity and mortality in CF patients. Cyclic di-GMP and cyclic AMP are second messengers regulating the bacterial lifestyle transition in response to environmental signals. We aimed to investigate the effects of extracellular pH and bicarbonate on intracellular c-di-GMP and cAMP levels, and on biofilm formation. P. aeruginosa was inoculated in a brain–heart infusion medium supplemented with 25 and 50 mM NaCl in ambient air (pH adjusted to 7.4 and 7.7 respectively), or with 25 and 50 mM NaHCO3 in 5% CO2 (pH 7.4 and 7.7). After 16 h incubation, c-di-GMP and cAMP were extracted and their concentrations determined. Biofilm formation was investigated using an xCelligence real-time cell analyzer and by crystal violet assay. Our results show that HCO3− exposure decreased c-di-GMP and increased cAMP levels in a dose-dependent manner. Biofilm formation was also reduced after 48 h exposure to HCO3−. The reciprocal changes in second messenger concentrations were not influenced by changes in medium pH or osmolality. These findings indicate that HCO3−&nbsp, per se modulates the levels of c-di-GMP and cAMP, thereby inhibiting biofilm formation and promoting the planktonic lifestyle of the bacteria.

The human gut microbiota has adapted to the presence of antimicrobial peptides (AMPs), which are ancient components of immune defence. Despite its medical importance, it has remained unclear whether AMP resistance genes in the gut microbiome are available for genetic exchange between bacterial species. Here, we show that AMP resistance and antibiotic resistance genes differ in their mobilization patterns and functional compatibilities with new bacterial hosts. First, whereas AMP resistance genes are widespread in the gut microbiome, their rate of horizontal transfer is lower than that of antibiotic resistance genes. Second, gut microbiota culturing and functional metagenomics have revealed that AMP resistance genes originating from phylogenetically distant bacteria have only a limited potential to confer resistance in Escherichia coli, an intrinsically susceptible species. Taken together, functional compatibility with the new bacterial host emerges as a key factor limiting the genetic exchange of AMP resistance genes. Finally, our results suggest that AMPs induce highly specific changes in the composition of the human microbiota, with implications for disease risks. Antimicrobial peptide resistance genes are found to be widespread in the gut microbiome but are exchanged at lower rates compared to antibiotic resistance genes, with functional compatibility between bacteria being important for gene exchange.

The human gut microbiota has adapted to the presence of antimicrobial peptides (AMPs) that are ancient components of immune defence. Despite important medical relevance, it has remained unclear whether AMP resistance genes in the gut microbiome are available for genetic exchange between bacterial species. Here we show that AMP- and antibiotic-resistance genes differ in their mobilization patterns and functional compatibilities with new bacterial hosts. First, whereas AMP resistance genes are widespread in the gut microbiome, their rate of horizontal transfer is lower than that of antibiotic resistance genes. Second, gut microbiota culturing and functional metagenomics revealed that AMP resistance genes originating from phylogenetically distant bacteria only have a limited potential to confer resistance inEscherichia coli, an intrinsically susceptible species. Third, the phenotypic impact of acquired AMP resistance genes heavily depends on the genetic background of the recipient bacteria. Taken together, functional compatibility with the new bacterial host emerges as a key factor limiting the genetic exchange of AMP resistance genes. Finally, our results suggest that AMPs induce highly specific changes in the composition of the human microbiota with implications for disease risks.

Biohydrogen production from synthetic wastewater as substrate was studied in anaerobic small scale batch reactors. Enriched anaerobic mixed consortia sampled from various environments were used as parent inocula to start the bioreactors. Selective enrichments were achieved by various physical and chemical pretreatments and changes in the microbial communities were monitored by metagenomic and molecular diagnostics approaches. Experimental data showed the feasibility of biohydrogen production using synthetic wastewater as substrate. The hydrogen generation capability of the different mixed consortia is clearly dependent on the pretreatment methods. The described approach opens the possibility for an alternative way towards simultaneous wastewater treatment and renewable energy generation.

The green alga Chlamydomonas reinhardtii is capable of photoproducing molecular hydrogen following sulphur deprivation, which results in anaerobiosis and a suppression of oxygen evolution and thus an alleviation of the inhibitory effect of oxygen on the hydrogenase. At the same time it transiently maintains a limited supply of electrons arising from photosystem II (PSII) to the hydrogenase (Melis and Happe Plant Physiol 2001; 127:740–748). In this work, using fast chl a fluorescence and P700 measurements, we show that ascorbate (Asc), a naturally occurring PSII alternative electron donor, is capable of donating electrons to PSII in heat-treated and sulphur-deprived cells and this can be significantly accelerated by supplementing the culture with 10 mM Asc. It also enhances, about three-fold, the photoproduction of hydrogen in cells subjected to sulphur deprivation as shown by gas chromatography. Similar stimulation was obtained in the presence of diphenylcarbazide (DPC), an artificial PSII electron donor. Asc and DPC also facilitated the anaerobiosis of cells, probably via super reducing the oxygen evolving complex while feeding electrons to PSII reaction centres and the linear electron transport chain, and ultimately to the hydrogenase – as shown by the significant DCMU-sensitivity of the light-induced Asc- and DPC-dependent re-reduction of P700+ and hydrogen evolution.

Purple sulfur phototrophic bacteria accumulate various storage materials, such as sulfur globules, glycogen or polyhydroxy alkanoates (PHAs) under appropriate conditions. The formation of these materials requires reducing power which might be recovered upon their breakdown. This work aims at the understanding of the metabolism of PHA and its link to the nitrogenase mediated in vivo H 2 evolution in Thiocapsa roseopersicina BBS. The strain could accumulate 30% of the dry cell weight in the form of PHAs. Analysis of the genome sequence revealed the loci involved in PHAs synthesis and degradation. Phylogenetic analysis indicated independent evolution of the anabolic and catabolic proteins. A mutant carrying deleted PHA biosynthesis genes has been created in a host containing nitrogenase but none of the hydrogenases. Determination of the H 2 evolving capacity of the mutant revealed significantly reduced H 2 production in PHA deficient cells. Addition of excess electron sources such as thiosulfate stimulated the H 2 production via multiple effects.

In nature, H2 production in Chlamydomonas reinhardtii serves as a safety valve during the induction of photosynthesis in anoxia, and it prevents the over-reduction of the photosynthetic electron transport chain. Sulphur deprivation of C. reinhardtii also triggers a complex metabolic response resulting in the induction of various stress-related genes, down-regulation of photosynthesis, the establishment of anaerobiosis and expression of active hydrogenase. Photosystem II (PSII) plays dual role in H2 production because it supplies electrons but the evolved O2 inhibits the hydrogenase. Here, we show that upon sulphur deprivation, the ascorbate content in C. reinhardtii increases about 50-fold, reaching the mM range; at this concentration, ascorbate inactivates the Mn-cluster of PSII, and afterwards, it can donate electrons to tyrozin Z(+) at a slow rate. This stage is followed by donor-side-induced photoinhibition, leading to the loss of charge separation activity in PSII and reaction centre degradation. The time point at which maximum ascorbate concentration is reached in the cell is critical for the establishment of anaerobiosis and initiation of H2 production. We also show that ascorbate influenced H2 evolution via altering the photosynthetic electron transport rather than hydrogenase activity and starch degradation.

Aerobic methane generation was demonstrated earlier in plants and eukaryotes under various stress conditions. Our aims were to develop a real-time and noninvasive detection system for monitoring the methane production of small animals and humans with our without exposure to various treatments. A near-infrared diode laser technique was employed with photoacoustic spectroscopy to monitor a methane-containing atmosphere online. The whole-body methane generation of anesthetized mice and rats was determined under baseline conditions and following reduction of the intestinal methanogenic flora or after lipopolysaccharide administration. Single-breath methane analyses were also carried out in a cross-sectional clinical study in order to obtain comparative human data. The whole-body methane production of mice was significantly decreased after antibiotic treatment (M: 1.71 ppm cm(-2) 10(3); p25: 1.5 ppm cm(-2) 10(3); p75: 2.11 ppm cm(-2) 10(3)) and increased significantly in endotoxemia (M: 4.53 ppm cm(-2) 10(3); p25: 4.37 ppm cm(-2) 10(3); p75: 5.38 ppm cm(-2) 10(3)), while no difference was observed between the rat groups. The methane content of the exhaled breath in humans was found to be between 0 and 37 ppm. Photoacoustic spectroscopy is a reliable tool with which to monitor the in vivo dynamics of stress-induced methane production in laboratory animals, even in a very low concentration range.

Background and aim Common chickweed (Stellaria media) tea has traditionally been applied for treatment of various metabolic diseases including diabetes in folk medicine; however, experimental evidence to support this practice is lacking. Therefore, we aimed to assess the effect of Stellaria media tea on glucose homeostasis and cardiac performance in a rat model of diabetes. Experimental procedure Hot water extract of Stellaria media herb were analyzed and used in this study, where diabetes was induced by fructose-enriched diet supplemented with a single injection of streptozotocin. Half of the animals received Stellaria media tea (100 mg/kg) by oral gavage. At the end of the 20-week experimental period, blood samples were collected and isolated working heart perfusions were performed. Results and conclusion Compared to the animals receiving standard chow, serum fasting glucose level was increased and glucose tolerance was diminished in diabetic rats. Stellaria media tea did not affect significantly fasting hyperglycemia and glucose intolerance; however, it attenuated diabetes-induced deterioration of cardiac output and cardiac work. Analysis of the chemical composition of Stellaria media tea suggested the presence of rutin and various apigenin glycosides which have been reported to alleviate diabetic cardiomyopathy. Moreover, Stellaria media prevented diabetes-induced increase in cardiac STAT3 phosphorylation. We demonstrated for the first time that Stellaria media tea may beneficially affect cardiac dysfunction induced by diabetes without improvement of glucose homeostasis. Rutin and/or apigenin glycosides as well as modulation of STAT3 signaling may be implicated in the protection of Stellaria media tea against diabetic cardiomyopathy.