Methanethiol-dependent dimethylsulfide production in soil environments

Dimethylsulfide (DMS) is an environmentally important trace gas with roles in sulfur cycling, signalling to higher organisms and in atmospheric chemistry. DMS is believed to be predominantly produced in marine environments via microbial degradation of the osmolyte dimethylsulfoniopropionate (DMSP). However, significant amounts of DMS are also generated from terrestrial environments, for example, peat bogs can emit ~6 μmol DMS m−2 per day, likely via the methylation of methanethiol (MeSH). A methyltransferase enzyme termed ‘MddA’, which catalyses the methylation of MeSH, generating DMS, in a wide range of bacteria and some cyanobacteria, may mediate this process, as the mddA gene is abundant in terrestrial metagenomes. This is the first study investigating the functionality of MeSH-dependent DMS production (Mdd) in a wide range of aerobic environments. All soils and marine sediment samples tested produced DMS when incubated with MeSH. Cultivation-dependent and cultivation-independent methods were used to assess microbial community changes in response to MeSH addition in a grassland soil where 35.9% of the bacteria were predicted to contain mddA. Bacteria of the genus Methylotenera were enriched in the presence of MeSH. Furthermore, many novel Mdd+ bacterial strains were isolated. Despite the abundance of mddA in the grassland soil, the Mdd pathway may not be a significant source of DMS in this environment as MeSH addition was required to detect DMS at only very low conversion rates

Bacterial SBP56 identified as a Cu-dependent methanethiol oxidase widely distributed in the biosphere

Oxidation of methanethiol (MT) is a significant step in the sulfur cycle. MT is an intermediate of metabolism of globally significant organosulfur compounds including dimethylsulfoniopropionate (DMSP) and dimethylsulfide (DMS), which have key roles in marine carbon and sulfur cycling. In aerobic bacteria, MT is degraded by a MT oxidase (MTO). The enzymatic and genetic basis of MT oxidation have remained poorly characterized. Here, we identify for the first time the MTO enzyme and its encoding gene (mtoX) in the DMS-degrading bacterium Hyphomicrobium sp. VS. We show that MTO is a homotetrameric metalloenzyme that requires Cu for enzyme activity. MTO is predicted to be a soluble periplasmic enzyme and a member of a distinct clade of the Selenium-binding protein (SBP56) family for which no function has been reported. Genes orthologous to mtoX exist in many bacteria able to degrade DMS, other one-carbon compounds or DMSP, notably in the marine model organism Ruegeria pomeroyi DSS-3, a member of the Rhodobacteraceae family that is abundant in marine environments. Marker exchange mutagenesis of mtoX disrupted the ability of R. pomeroyi to metabolize MT confirming its function in this DMSP-degrading bacterium. In R. pomeroyi, transcription of mtoX was enhanced by DMSP, methylmercaptopropionate and MT. Rates of MT degradation increased after pre-incubation of the wild-type strain with MT. The detection of mtoX orthologs in diverse bacteria, environmental samples and its abundance in a range of metagenomic data sets point to this enzyme being widely distributed in the environment and having a key role in global sulfur cycling.The ISME Journal advance online publication, 24 October 2017; doi:10.1038/ismej.2017.148

Ceremonial plant consumption at Middle Bronze Age Büklükale, Kırıkkale Province, central Turkey

A shaft-like room at the Middle Bronze Age site of Büklükale in central Turkey preserved a rich archaeobotanical assemblage of charred and mineralised plant remains, dominated by fruits, spices and nuts mixed with probable bread and wood charcoals. The remains were recovered in association with numerous ceramic vessels, jewellery and exotic artefacts. We combine identification and analysis of the seeds and wood charcoals contained in this deposit with studies of Old Assyrian and Hittite textual records to investigate the circumstances of the assemblage’s formation and its significance for further understanding trade and plant consumption in Bronze Age Anatolia. We present the earliest archaeobotanical example in the region of rare and exotic plant species being consumed in the context of one or more social gatherings, including those possibly linked to ceremonial or ritual events. This offers new insights into the role of plants in the economic and social life of the southwest Asian Bronze Age, as well as the role of commensality and feasting in early states

The renin-angiotensin-aldosterone system during haemodialysis with acetate or bicarbonate at different dialysate sodium concentrations

The hormones of the renin angiotensin aldosterone system were measured during regular haemodialysis with acetate or bicarbonate at dialysate sodium concentrations of 135, 140, 145, and 150 mmol/l. Plasma renin activity and aldosterone concentration were higher during acetate haemodialysis than during bicarbonate haemodialysis. At lower dialysate sodium concentrations, plasma renin activity (acetate dialysis and bicarbonate dialysis) and aldosterone concentration (only acetate dialysis) were higher than they were at higher dialysate sodium concentrations. Plasma renin activity increased during acetate dialysis, but did not change during bicarbonate dialysis. Aldosterone and potassium concentrations were positively correlated. Aldosterone decreased during haemodialysis (increase to predialysis values at the end of haemodialysis (4 h) at lower dialysate sodium concentrations). It is concluded that the renin angiotensin aldosterone system is activated more during acetate dialysis than during bicarbonate dialysis. Aldosterone concentrations seem to be related more closely to serum potassium than to renin-angiotensin-aldosterone system and to serum sodium intradialytically

Regulation of plasma aldosterone during hemodialysis

In order to clarify the influence of serum potassium, serum sodium and plasma angiotensin II concentrations on aldosterone release during hemodialysis (HD), six chronic hemodialysis patients were studied during HD with varying dialysate sodium concentrations and different buffers. Plasma aldosterone concentrations were higher during acetate than bicarbonate HD, during low sodium compared to high sodium HD, and were correlated inversely to serum sodium concentrations. The decline in plasma aldosterone concentrations during HD paralleled the decrease in serum potassium concentrations, and plasma aldosterone concentrations were correlated with serum potassium concentrations. In addition, plasma aldosterone and plasma angiotensin II concentrations were correlated significantly. It is proposed that serum potassium and the renin-angiotensin system are the main factors of aldosterone release during hemodialysis, while serum sodium per se seems to be of less importance. The dialysate buffer employed also plays a role in aldosterone regulation (via the renin-angiotensin system)

Has The World Changed? My Neighbor Might Know Effects of Social Context on Routine Deviation

In two experiments we studied the effects of behavioral models on routine deviation decisions in observers. Participants repeatedly chose among four card-deck lotteries together with a human model (confederate, Exp. 1) or a non-human model (computer, Exp. 2) that made correct decisions in the majority of the trials. In a learning phase, participants acquired a choice routine (preferring one deck over others). In a subsequent test phase, participants had to adapt to changes in the payoff structure that required them to deviate from their routine. We found a strong tendency to maintain the routine despite negative feedback (routine effect). In a social situation (Exp.1), models decrease routine effects more intensely than in non social situations (Exp.2). The process of adaptation follows a belief updating process. Results indicate that the model effect is not due to an increase of the sample of relevant information nor to application of a simply copy heuristic. Rather, deviation models may provide a cue for change that fosters reevaluation of the situation in the observer