scholarly journals Direct evidence for the role of microbial community composition in the formation of soil organic matter composition and persistence

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Luiz A. Domeignoz-Horta ◽  
Melissa Shinfuku ◽  
Pilar Junier ◽  
Simon Poirier ◽  
Eric Verrecchia ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Organic Matter ◽  
Microbial Community ◽  
Soil Organic Matter ◽  
Microbial Communities ◽  
Soil Carbon ◽  
Community Composition ◽  
Direct Evidence ◽  
Microbial Community Composition ◽  
Soil Matrix

AbstractThe largest terrestrial carbon sink on earth is soil carbon stocks. As the climate changes, the rate at which the Earth’s climate warms depends in part on the persistence of soil organic carbon. Microbial turnover forms the backbone of soil organic matter (SOM) formation and it has been recently proposed that SOM molecular complexity is a key driver of stability. Despite this, the links between microbial diversity, chemical complexity and biogeochemical nature of SOM remain missing. Here we tested the hypotheses that distinct microbial communities shape the composition of SOM, and microbial-derived SOM has distinct decomposition potential depending on its community of origin. We inoculated microbial communities of varying diversities into a model soil matrix amended with simple carbon (cellobiose) and measured the thermal stability of the resultant SOM. Using a Rock-Eval® ramped thermal analysis, we found that microbial community composition drives the chemical fingerprint of soil carbon. While diversity was not a driver of SOM composition, bacteria-only communities lead to more thermally labile soil C pools than communities with bacteria and fungi. Our results provide direct evidence for a link between microbial community structure, SOM composition, and thermal stability. This evidence demonstrates the relevance of soil microorganisms in building persistent SOM stocks.

Soil microbial communities in microaggregates are less affected by top-down effects of collembolans than those in macroaggregates

2021 ◽  
Author(s):  
Amandine Erktan ◽  
MD Ekramul Haque ◽  
Jérôme Cortet ◽  
Paul Henning Krogh ◽  
Stefan Scheu
Keyword(s):  
Microbial Community ◽  
Microbial Communities ◽  
Community Composition ◽  
Trophic Interactions ◽  
Phospholipid Fatty Acid ◽  
Microbial Community Composition ◽  
Soil Microbial Communities ◽  
Trophic Levels ◽  
Soil Matrix ◽  
Fungal Abundance

<p>Trophic regulation of microbial communities is receiving growing interest in soil ecology. Most studies investigated the effect of higher trophic levels on microbial communities at the bulk soil level. However, microbes are not equally accessible to consumers. They may be hidden in small pores and thus protected from consumers, suggesting that trophic regulation may depend on the localization of microbes within the soil matrix. As microaggregates (< 250 µm) usually are more stable than macroaggregates (> 250 µm) and embedded in the latter, we posit that they will be less affected by trophic regulations than larger aggregates. We quantified the effect of four contrasting species of collembolans (Ceratophysella denticulata, Protaphorura fimata, Folsomia candida, Sinella curviseta) on the microbial community composition in macro- (250 µm – 2mm) and microaggregates (50 – 250 µm). To do so, we re-built consumer-prey systems comprising remaining microbial background (post-autoclaving), fungal prey (Chaetomium globosum), and collembolan species (added as single species or combined). After three months, we quantified microbial community composition using phospholipid fatty acid markers (PLFAs). We found that the microbial communities in macroaggregates were more affected by the addition of collembolans than the communities in microaggregates. In particular, the fungal-to-bacterial (F:B) ratio significantly decreased in soil macroaggregates in the presence of collembolans. In the microaggregates, the F:B ratio remained lower and unaffected by collembolan inoculation. Presumably, fungal hyphae were more abundant in macroaggregates because they offered more habitat space for them, and the collembolans reduced fungal abundance because they consumed them. On the contrary, microaggregates presumably contained microbial communities protected from consumers. In addition, collembolans increased the formation of macroaggregates but did not influence their stability, despite their negative effect on fungal abundance, a well-known stabilizing agent. Overall, we show that trophic interactions between microbial communities and collembolans depend on the aggregate size class considered and, in return, soil macroaggregation is affected by these trophic interactions.</p>

Permafrost-derived dissolved organic matter character controls microbial community composition in Arctic coastal waters

2021 ◽  
Author(s):  
Anders Dalhoff Bruhn ◽  
Colin A. Stedmon ◽  
Jérôme Comte ◽  
Atsushi Matsuoka ◽  
Neik Jesse Speetjens ◽  
...  
Keyword(s):  
Organic Matter ◽  
Microbial Community ◽  
Microbial Communities ◽  
Community Composition ◽  
Relative Abundance ◽  
Microbial Community Composition ◽  
The Arctic ◽  
Glacial Deposit ◽  
Deposit Type ◽  
Lacustrine Deposit

<p>Climate warming is accelerating erosion rates along permafrost-dominated Arctic coasts. To study the impact of erosion on marine microbial community composition and growth in the Arctic coastal zone, dissolved organic matter (DOM) from three representative glacial landscapes (fluvial, lacustrine and moraine) along the Yukon coastal plain, are provided as substrate to marine bacteria using a chemostat setup. Our results indicate that chemostat cultures with a flushing rate of approximately a day provide comparable DOM bioavailability estimates to those from bottle experiments lasting weeks to months. DOM composition (inferred from UV-Visible spectroscopy) and biodegradability (inferred from DOC concentration, bacterial production and respiration) significantly differed between the three glacial deposit types. DOM from fluvial and moraine deposit types shows more terrestrial characteristics with lower aromaticity (S<sub>R</sub>: 0.63 (±0.02), SUVA<sub>254</sub>: 1.65 (±0.06) respectively S<sub>R</sub>: 0.68 (±0.00), SUVA<sub>254</sub>: 1.17 (±0.06)) compared to the lacustrine deposit type (S<sub>R</sub>: 0.71 (±0.02), SUVA<sub>254</sub>: 2.15 (±0.05)). The difference in composition of DOM corresponds with the development of three distinct microbial communities, with a dominance of Alphaproteobacteria for fluvial and lacustrine deposit types (relative abundance 0.67 and 0.87 respectively) and a dominance of Gammaproteobacteria for moraine deposit type (relative abundance 0.88). Bacterial growth efficiency (BGE) is 66% for moraine-derived DOM, while 13% and 28% for fluvial-derived and lacustrine-derived DOM respectively. The three microbial communities therefore differ in their net effect on DOM utilization. The higher BGE value for moraine-derived DOM was found to be due to a larger proportion of labile colourless DOM. The results from this study, therefore indicate a substrate control of marine microbial community composition and activities, suggesting that the effect of permafrost thaw and erosion in the Arctic coastal zone will depend on subtle differences in DOM related to glacial deposit types. These differences further determines the speed and extent of DOM mineralization and thereby carbon channelling into biomass in the microbial food web. We therefore conclude that marine microbes strongly respond to the input of terrestrial DOM released during coastal erosion of Arctic glacial landscapes.</p>

scholarly journals The role of microbial diversity in the formation of soil organic matter quality and persistence

2021 ◽  
Author(s):  
Luiz A. Domeignoz-Horta ◽  
Melissa Shinfuku ◽  
Pilar Junier ◽  
Simon Poirier ◽  
Eric Verrecchia ◽  
...  
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Microbial Diversity ◽  
Microbial Communities ◽  
Soil Carbon ◽  
Organic Matter Quality ◽  
Soil System ◽  
Soil Matrix ◽  
Model Soil ◽  
Molecular Complexity

AbstractThe largest terrestrial carbon sink on earth is soil carbon stocks. As the climate changes, the rate at which the Earth’s climate warms depends in part on the persistence of soil organic carbon. Microbial turnover forms the backbone of soil organic matter (SOM) formation and it has been recently proposed that SOM molecular complexity is a key driver of stability. Despite this, the links between microbial diversity, chemical complexity and biogeochemical nature of soil organic matter remain missing. Here we used a model soil system to test the hypothesis that more diverse microbial communities generate more stable soil organic matter. We inoculated microbial communities of varying diversities into an model soil matrix amended with simple carbon, and measured the thermal stability of the resultant soil organic matter. Using a novel data analysis approach with Rock-Eval® ramped thermal analysis, we found that microbial community diversity drives the chemical fingerprint of soil organic matter. Bacteria-only and low diversity communities lead to less chemically-diverse and more thermally-labile soil carbon pools than highly diverse communities. Our results provide direct evidence for a link between microbial diversity, molecular complexity and SOM stability. This evidence demonstrates the benefits of managing soils for maximum biological diversity as a means of building persistent SOM stocks.ClassificationBiological Sciences: Ecology

scholarly journals Effects of Soil Organic Matter Properties and Microbial Community Composition on Enzyme Activities in Cryoturbated Arctic Soils

PLoS ONE ◽  
2014 ◽  
Vol 9 (4) ◽  
pp. e94076 ◽  
Author(s):  
Jörg Schnecker ◽  
Birgit Wild ◽  
Florian Hofhansl ◽  
Ricardo J. Eloy Alves ◽  
Jiří Bárta ◽  
...  
Keyword(s):  
Organic Matter ◽  
Microbial Community ◽  
Soil Organic Matter ◽  
Community Composition ◽  
Enzyme Activities ◽  
Microbial Community Composition ◽  
Arctic Soils

Composition of low molecular weight organic substances affect total soil microbial activity independently of community composition.

2020 ◽  
Author(s):  
Louis J.P. Dufour ◽  
Anke. M. Herrmann ◽  
Julie Leloup ◽  
Cédric Przybylski ◽  
Luc Abbadie ◽  
...  
Keyword(s):  
Organic Matter ◽  
Microbial Community ◽  
Microbial Communities ◽  
Microbial Activity ◽  
Community Composition ◽  
Metabolic Pathways ◽  
Heat Dissipation ◽  
Energy Content ◽  
Microbial Community Composition ◽  
Total Heat

<p>It has recently been suggested that microbial-derived material is an important constituent of soil organic matter, and accumulation of organic matter in soil is related to microbial activity and the composition of the microbial communities present. However, microbial activity is generally intimately related to the properties of the carbon substrate (e.g. molecular diversity, energy content) available for decomposition. It is important, therefore, to understand in more detail what the drivers of microbial activity and their associated metabolic pathways are: the composition of the microbial communities or the properties of the available organic substrate.</p><p>Water extractable organic matter from 6 different grassland and forest soils were added cross-wise to samples of each of the soils. The total heat dissipation was measured by isothermal calorimetry during a 23 h incubation period. Heat dissipation is a measure of total metabolic activity in the soil. The total CO<sub>2</sub> emission was also determined, by gas chromatography-mass spectrometry. The elemental composition of low molecular weight organic substances (LMWOS) was obtained by Fourier-Transform Ion Cyclotron Resonance Mass Spectrometry, which allowed us to calculate the Nominal Oxidation State of Carbon (NOSC) from each exact molecular mass detected. The NOSC is related to the energy content of the molecules. The microbial composition was determined by 16S rRNA gene sequencing. This experimental design allowed us to evaluate potential links between microbial community composition and their metabolic pathways when different LMWOS are undergoing decomposition.</p><p>First, we found that the total heat dissipated and CO<sub>2</sub> emitted were associated with differences in the composition of LMWOS, independent of microbial community composition in the soil. We observed that the median of the total CO<sub>2</sub> emission was positively correlated with the weighted sum of the NOSC of each detected LMWOS. These results emphasise that a supply in available substrate with lower energy density (i.e. higher NOSC) may result in an increase in decarboxylation processes. Furthermore, total heat dissipated but not CO<sub>2</sub> was positively correlated to the molecular richness of LMWOS. This indicates that substrate with a higher molecular richness include also other metabolic pathways where CO<sub>2</sub> is not a decomposition end-product. Finally, we observed three different dynamics of heat dissipation during the 23 h incubation period. These dynamics were related to the microbial communities, but were independent of the LMWOS composition. The dynamic of heat dissipation were summarised by a Q<sub>t50</sub> index, i.e. the time required to release half of the heat dissipated in 23 h. The Q<sub>t50</sub> index was significantly correlated to the relative abundance of different bacterial taxa. In conclusion, whilst the short-term dynamics of substrate use appear to be associated with microbial community composition, the overall activity is more closely related to the composition of the available substrate.</p>

scholarly journals Antarctic Water Tracks: Microbial Community Responses to Variation in Soil Moisture, pH, and Salinity

2021 ◽  
Vol 12 ◽  
Author(s):  
Scott F. George ◽  
Noah Fierer ◽  
Joseph S. Levy ◽  
Byron Adams
Keyword(s):  
Microbial Community ◽  
Microbial Communities ◽  
Community Composition ◽  
Environmental Conditions ◽  
Microbial Community Composition ◽  
Soil Microbial Communities ◽  
Vapor Flow ◽  
Arid Soils ◽  
Opposite Pattern ◽  
Dry Valley

Ice-free soils in the McMurdo Dry Valleys select for taxa able to cope with challenging environmental conditions, including extreme chemical water activity gradients, freeze-thaw cycling, desiccation, and solar radiation regimes. The low biotic complexity of Dry Valley soils makes them well suited to investigate environmental and spatial influences on bacterial community structure. Water tracks are annually wetted habitats in the cold-arid soils of Antarctica that form briefly each summer with moisture sourced from snow melt, ground ice thaw, and atmospheric deposition via deliquescence and vapor flow into brines. Compared to neighboring arid soils, water tracks are highly saline and relatively moist habitats. They represent a considerable area (∼5–10 km2) of the Dry Valley terrestrial ecosystem, an area that is expected to increase with ongoing climate change. The goal of this study was to determine how variation in the environmental conditions of water tracks influences the composition and diversity of microbial communities. We found significant differences in microbial community composition between on- and off-water track samples, and across two distinct locations. Of the tested environmental variables, soil salinity was the best predictor of community composition, with members of the Bacteroidetes phylum being relatively more abundant at higher salinities and the Actinobacteria phylum showing the opposite pattern. There was also a significant, inverse relationship between salinity and bacterial diversity. Our results suggest water track formation significantly alters dry soil microbial communities, likely influencing subsequent ecosystem functioning. We highlight how Dry Valley water tracks could be a useful model system for understanding the potential habitability of transiently wetted environments found on the surface of Mars.

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