Response of Methanogens in Arctic Sediments to Temperature and Methanogenic Substrate Availability

Although cold environments are major contributors to global biogeochemical cycles, comparatively little is known about their microbial community function, structure, and limits of activity. In this study a microcosm based approach was used to investigate the effects of temperature, and methanogenic substrate amendment, (acetate, methanol and H2/CO2) on methanogen activity and methanogen community structure in high Arctic wetlands (Solvatnet and Stuphallet, Svalbard). Methane production was not detected in Stuphallet sediment microcosms (over a 150 day period) and occurred within Solvatnet sediments microcosms (within 24 hours) at temperatures from 5 to 40°C, the maximum temperature being at far higher than in situ maximum temperatures (which range from air temperatures of -1.4 to 14.1°C during summer months). Distinct responses were observed in the Solvatnet methanogen community under different short term incubation conditions. Specifically, different communities were selected at higher and lower temperatures. At lower temperatures (5°C) addition of exogenous substrates (acetate, methanol or H2/CO2) had no stimulatory effect on the rate of methanogenesis or on methanogen community structure. The community in these incubations was dominated by members of the Methanoregulaceae/WCHA2-08 family-level group, which were most similar to the psychrotolerant hydrogenotrophic methanogen Methanosphaerula palustris strain E1-9c. In contrast, at higher temperatures, substrate amendment enhanced methane production in H2/CO2 amended microcosms, and played a clear role in structuring methanogen communities. Specifically, at 30°C members of the Methanoregulaceae/WCHA2-08 predominated following incubation with H2/CO2, and Methanosarcinaceaeand Methanosaetaceae were enriched in response to acetate addition. These results may indicate that in transiently cold environments, methanogen communities can rapidly respond to moderate short term increases in temperature, but not necessarily to the seasonal release of previously frozen organic carbon from thawing permafrost soils. However, as temperatures increase such inputs of carbon will likely have a greater influence on methane production and methanogen community structure. Understanding the action and limitations of anaerobic microorganisms within cold environments may provide information which can be used in defining region-specific differences in the microbial processes; which ultimately control methane flux to the atmosphere

Distribution of thermophilic endospores in a temperate estuary indicate that dispersal history structures sediment microbial communities

Endospores of thermophilic bacteria are found in cold and temperate sediments where they persist in a dormant state. As inactive endospores that cannot grow at the low ambient temperatures, they are akin to tracer particles in cold sediments, unaffected by factors normally governing microbial biogeography (e.g., selection, drift, mutation). This makes thermophilic endospores ideal model organisms for studying microbial biogeography since their spatial distribution can be directly related to their dispersal history. To assess dispersal histories of estuarine bacteria, thermophilic endospores were enriched from sediments along a freshwater‐to‐marine transect of the River Tyne in high temperature incubations (50°C). Dispersal histories for 75 different taxa indicated that the majority of estuarine endospores were of terrestrial origin; most closely related to bacteria from warm habitats associated with industrial activity. A subset of the taxa detected were marine derived, with close relatives from hot deep marine biosphere habitats. These patterns are consistent with the sources of sediment in the River Tyne being predominantly terrestrial in origin. The results point to microbial communities in estuarine and marine sediments being structured by bi‐directional currents, terrestrial run‐off and industrial effluent as vectors of passive dispersal and immigration

An Unexpectedly Broad Thermal and Salinity-Tolerant Estuarine Methanogen Community

Moderately thermophilic (Tmax, ~55 °C) methanogens are identified after extended enrichments from temperate, tropical and low-temperature environments. However, thermophilic methanogens with higher growth temperatures (Topt ≥ 60 °C) are only reported from high-temperature environments. A microcosm-based approach was used to measure the rate of methane production and methanogen community structure over a range of temperatures and salinities in sediment from a temperate estuary. We report short-term incubations (<48 h) revealing methanogens with optimal activity reaching 70 °C in a temperate estuary sediment (in situ temperature 4–5 °C). While 30 °C enrichments amended with acetate, H2 or methanol selected for corresponding mesophilic trophic groups, at 60 °C, only hydrogenotrophs (genus Methanothermobacter) were observed. Since these methanogens are not known to be active under in situ temperatures, we conclude constant dispersal from high temperature habitats. The likely provenance of the thermophilic methanogens was studied by enrichments covering a range of temperatures and salinities. These enrichments indicated that the estuarine sediment hosted methanogens encompassing the global activity envelope of most cultured species. We suggest that estuaries are fascinating sink and source environments for microbial function study

The microbiology of rebuilding soils with water treatment residual co‐amendments: Risks and benefits

Water treatment residuals (WTR) are sludges from the potable water treatment process, currently largely destined for landfill. This waste can be diverted to rebuild degraded soils, aligning with the UN's Sustainable Development Goals 12 (Consumption and Production) and 15 (Terrestrial Ecosystems). Biosolids are tested against stringent pathogen guidelines, yet few studies have explored the microbial risk of WTR land application, despite anthropogenic impacts on water treatment. Here, the microbial risks and benefits of amending nutrient-poor sandy soil with WTR were explored. It was shown that the culturable pathogen load of wet and dry WTR did not warrant pre-processing before land application, according to South African national quality guidelines, with fecal coliforms not exceeding 104 CFU/gdw in wet sludges sampled from four South African and Zimbabwean water treatment plants, and decreasing upon drying and processing. There was no culturable pathogenic (fecal coliforms, enterococci, Salmonella and Shigella) regrowth in soil incubations amended with dry WTR. However, the competition (microbial load and diversity) introduced by a WTR co-amendment did not limit pathogen survival in soils amended with biosolids. The application of WTR to nutrient-poor sandy soils for wheat (Triticum aestivum L.) growth improved the prokaryotic and eukaryotic culturable cell concentrations, similar to compost. However, the compost microbiome more significantly impacted the bacterial beta diversity of the receiving soil than WTR, analyzed with ARISA. Thus, although there was a low pathogen risk for WTR-amendment in receiving soils, and total soil microbial loads were increased, microbial diversity was more significantly enhanced by compost than WTR

The toxicity of the methylimidazolium ionic liquids, with a focus on M8OI and hepatic effects

Ionic liquids are a diverse range of charged chemicals with low volatility and often liquids at ambient temperatures. This characteristic has in part lead to them being considered environmentally-friendly replacements for existing volatile solvents. However, methylimidazolium ionic liquids are slow to break down in the environment and a recent study at Newcastle detected 1 octyl 3 methylimidazolium (M8OI) – an 8 carbon variant methylimidazolium ionic liquid - in soils in close proximity to a landfill site. The current M8OI toxicity database in cultured mammalian cells, in experimental animal studies and in model indicators of environmental impact are reviewed. Selected analytical data from the Newcastle study suggest the soils in close proximity to the landfill site, an urban soil lacking overt contamination, had variable levels of M8OI. The potential for M8OI - or a structurally related ionic liquid – to trigger primary biliary cholangitis (PBC), an autoimmune liver disease thought to be triggered by an unknown agent(s) in the environment, is reviewed

An Unexpectedly Broad Thermal and Salinity-Tolerant Estuarine Methanogen Community

Moderately thermophilic (Tmax, ~55 &deg;C) methanogens are identified after extended enrichments from temperate, tropical and low-temperature environments. However, thermophilic methanogens with higher growth temperatures (Topt &ge; 60 &deg;C) are only reported from high-temperature environments. A microcosm-based approach was used to measure the rate of methane production and methanogen community structure over a range of temperatures and salinities in sediment from a temperate estuary. We report short-term incubations (&lt;48 h) revealing methanogens with optimal activity reaching 70 &deg;C in a temperate estuary sediment (in situ temperature 4&ndash;5 &deg;C). While 30 &deg;C enrichments amended with acetate, H2 or methanol selected for corresponding mesophilic trophic groups, at 60 &deg;C, only hydrogenotrophs (genus Methanothermobacter) were observed. Since these methanogens are not known to be active under in situ temperatures, we conclude constant dispersal from high temperature habitats. The likely provenance of the thermophilic methanogens was studied by enrichments covering a range of temperatures and salinities. These enrichments indicated that the estuarine sediment hosted methanogens encompassing the global activity envelope of most cultured species. We suggest that estuaries are fascinating sink and source environments for microbial function study

Carbon Dioxide and the Carbamate Post-Translational Modification

Carbon dioxide is essential for life. It is at the beginning of every life process as a substrate of photosynthesis. It is at the end of every life process as the product of post-mortem decay. Therefore, it is not surprising that this gas regulates such diverse processes as cellular chemical reactions, transport, maintenance of the cellular environment, and behaviour. Carbon dioxide is a strategically important research target relevant to crop responses to environmental change, insect vector-borne disease and public health. However, we know little of carbon dioxide’s direct interactions with the cell. The carbamate post-translational modification, mediated by the nucleophilic attack by carbon dioxide on N-terminal α-amino groups or the lysine ɛ-amino groups, is one mechanism by which carbon dioxide might alter protein function to form part of a sensing and signalling mechanism. We detail known protein carbamates, including the history of their discovery. Further, we describe recent studies on new techniques to isolate this problematic post-translational modification

Better Together: Water Treatment Residual and Poor-Quality Compost Improves Sandy Soil Fertility

Water treatment residual (WTR) is an underused clean water industry byproduct, generally disposed to landfill. This study assesses the benefits and risks of ferric-WTR as a soil amendment or co-amendment for plant growth in a nutrient-poor sandy soil. A 12-wk pot trial tested the efficacy of WTR and a locally available, low-quality, municipal compost as single (1, 5, and 12.5% dry mass) and co-amended treatments (1:1 WTR/compost ratio, at 2, 10, and 25%) on wheat (Triticum aestivum L.) growth in a sandy soil. The low total N content of the compost and low WTR P and K contents resulted in significantly lower (up to 50% lower, p < 0.05) plant biomass in single amendments compared with the control, whereas the highest co-amendment produced significantly higher plant biomass (33% higher, p < 0.05) than the control. This positive co-amendment effect on plant growth is attributed to balanced nutrient provision, with P and K from the compost and N from the WTR. Foliar micronutrient and Al levels showed no toxic accumulation, and co-amended foliar Mn levels increased from near deficient (20 mg kg−1) to sufficient (50 mg kg−1). Total WTR metals were well below maximum land application concentrations (USDA). Trace element bioavailability remained the same (Ni, Cu, and Hg) or significantly decreased (B, Al, Cr, Mn, Fe, Zn, As, and Cd; p < 0.05) during the pot trial. These results suggest, within this context, that a WTR–compost co-amendment is a promising soil improvement technology for increasing crop yields in sandy soils

Phylogenetic tree of a selection of archaeal partial 16S rRNA sequences obtained in this study (shown in bold with sample origin and OTU assignments based on ARDRA analysis, see S1 Table).

<p>Taxonomic assignments for all sequences (including those not shown in this tree) were made using the SILVA database <a href="http://www.arb-silva.de/" target="_blank">http://www.arb-silva.de</a>. All sequences were assigned to the Class <i>Methanomicrobia</i> and designated (see brackets) as 5 separate families in the class <i>Methanomicrobia</i> i.e. <i>Methanoregulaceae</i>/WCHA2-08 and <i>Methanospirillaceae</i> (order <i>Methanomicrobiales</i>); <i>Methanoflorentaceae</i> (order <i>Methanocellales</i>); <i>Methanosaetaceae</i> and <i>Methansarcinaceae</i> (order <i>Methanosarcinales</i>). *Clone sequence A142 was classified based on ARDRA analysis as OTU 2 but was found to be more distantly related than all other representative OTU 2 sequences albeit clustering within the same family-level group <i>Methanoregulaceae</i>/WCHA2-08.</p

Methane production rates over the incubation temperature range of 5 to 70°C from day 0 to 7 with or without methanogenic substrate addition.

<p>Methane production in BES controls was always very low (maximum 0.0107 ± 0.001 μmol CH₄ g^-1 DM d^-1 ± SE, n = 3).</p