scholarly journals Changes in Microbial Community Phylogeny and Metabolic Activity Along the Water Column Uncouple at Near Sediment Aphotic Layers in Fjords

2021 ◽  
Author(s):  
Sven P. Tobias-Hünefeldt ◽  
Stephen R. Wing ◽  
Federico Baltar ◽  
Sergio E. Morales
Keyword(s):  
Organic Matter ◽  
Microbial Community ◽  
Water Column ◽  
Microbial Activity ◽  
Community Composition ◽  
Microbial Community Composition ◽  
Leucine Incorporation ◽  
Metabolic Potential ◽  
Near Surface ◽  
Potential Activity

Abstract Fjords are semi-enclosed marine systems with unique physical conditions that influence microbial community composition and structure. Pronounced organic matter and physical condition gradients within fjords provide a natural laboratory for the study of changes in microbial phylogeny and metabolic potential in response to environmental conditions. Photosynthetic production in euphotic zones sustains deeper aphotic microbial activity via organic matter sinking, augmented by large terrestrial inputs. We profiled microbial functional potential (Biolog Ecoplates), bacterial abundance, heterotrophic production (3H-Leucine incorporation), and prokaryotic/eukaryotic community composition (16S and 18S rRNA amplicon gene sequencing) to link metabolic potential, activity, and community composition to known community drivers. Similar factors shaped metabolic potential, activity and community (prokaryotic and eukaryotic) composition across surface/near surface sites. However, increased metabolic diversity at near bottom (aphotic) sites reflected an organic matter influence from sediments. Photosynthetically produced particulate organic matter shaped the upper water column community composition and metabolic potential. In contrast, microbial activity at deeper aphotic waters were strongly influenced by other organic matter imput than sinking marine snow (e.g. sediment resuspension of benthic organic matter, remineralisation of terrestrially derived organic matter, etc.), severing the link between phylogeny and metabolic potential. Taken together, different organic matter sources shape microbial activity, but not community composition, in New Zealand fjords.

scholarly journals Changes in microbial community phylogeny and metabolic activity along the water column uncouple at near sediment aphotic layers in fjords

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sven P. Tobias-Hünefeldt ◽  
Stephen R. Wing ◽  
Federico Baltar ◽  
Sergio E. Morales
Keyword(s):  
Organic Matter ◽  
Community Structure ◽  
Microbial Community ◽  
Water Column ◽  
Microbial Activity ◽  
Community Composition ◽  
Microbial Community Composition ◽  
Leucine Incorporation ◽  
Metabolic Potential ◽  
Near Surface

AbstractFjords are semi-enclosed marine systems with unique physical conditions that influence microbial community composition and structure. Pronounced organic matter and physical condition gradients within fjords provide a natural laboratory for the study of changes in microbial community structure and metabolic potential in response to environmental conditions. Photosynthetic production in euphotic zones sustains deeper aphotic microbial activity via organic matter sinking, augmented by large terrestrial inputs. Previous studies do not consider both prokaryotic and eukaryotic communities when linking metabolic potential and activity, community composition, and environmental gradients. To address this gap we profiled microbial functional potential (Biolog Ecoplates), bacterial abundance, heterotrophic production (3H-Leucine incorporation), and prokaryotic/eukaryotic community composition (16S and 18S rRNA amplicon gene sequencing). Similar factors shaped metabolic potential, activity and community (prokaryotic and eukaryotic) composition across surface/near surface sites. However, increased metabolic diversity at near bottom (aphotic) sites reflected an organic matter influence from sediments. Photosynthetically produced particulate organic matter shaped the upper water column community composition and metabolic potential. In contrast, microbial activity at deeper aphotic waters were strongly influenced by other organic matter input than sinking marine snow (e.g. sediment resuspension of benthic organic matter, remineralisation of terrestrially derived organic matter, etc.), severing the link between community structure and metabolic potential. Taken together, different organic matter sources shape microbial activity, but not community composition, in New Zealand fjords.

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>

Organic matter additions to soil and effects on microbially mediated carbon cycling

2020 ◽  
Author(s):  
Rachel hasler ◽  
Mark pawlett ◽  
Jim harris ◽  
Helen bostock ◽  
Marc redmile-gordon
Keyword(s):  
Organic Matter ◽  
Microbial Community ◽  
Carbon Cycling ◽  
Community Composition ◽  
Soil Microbial Community ◽  
Microbial Community Composition ◽  
Soil Microbial ◽  
Horse Manure ◽  
Soil Microbial Community Composition

<p>The type of soil organic amendment selected can have profound implications for carbon cycling processes in soils. Understanding the link between this choice and its effect on the soil microbiome will improve our understanding of the capacity of these materials to improve carbon sequestration and cycling dynamics. Understanding and facilitating the lifestyle strategies of microorganisms processing organic matter is essential to improving our understanding of the terrestrial carbon cycle. This research focuses on utilising organic amendments to alter the indigenous soil microbial community composition and function to improve the capacity of the soil to cycle and store carbon in horticultural soils.  The effects of annual application of various organic fertilisers (peat, bracken, bark, horse manure, garden compost) in a long-term (10year) field experiment were explored. Sampling was completed pre and post application of organic matter within one season (following 10 years of applications) to identify which organic amendment was more effective in producing benefits to plants through improved soil organic matter and which amendments provide the greatest legacy effect on carbon cycling. The response of the soil microbial community composition (phospholipid fatty acid analysis) and carbon functional cycling dynamics (respiration using MicroResp™) were determined with a view to improving our understanding of the interaction between the materials applied and microbial processes. PCA of the MicroResp™ data identified that all treatments had a different functional profile compared to the control[PM1]  with peat being significantly different from all other treatments. Horse manure and bark differed significantly within a single growing season; prior and post organic matter addition in spring 2019.  Microbial biomass measurements for garden compost and horse manure were significantly higher following organic matter addition compared to all other treatments and the control[PM2] .  All treatments had a significant effect [PM3] on hot water extractable carbon and total carbon. Peat had a significantly different effect[PM4] , when compared to other treatments, on the soil PLFA profile and bark application significantly increased [PM5] the neutral lipid (NLFA) biomarker 16:1ω5.  Bark and horse manure application both significantly increased PLFA fungal biomarker 18:2ω6,9. No significant differences were found between the fungal/bacterial ratios of the organic matter additions prior to being added to the soil. These findings show that altering the resources available to the soil microbial community has a significant impact on soil microbial community composition and microbially mediated carbon cycling functionality. Increasing our understanding of how soil functions are altered by land management decisions will enable better informed predictions of the long-term benefits of organic matter applications on carbon sequestration and cycling dynamics.</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>

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