Measure Of Microbial Activity Research Articles

Microbial growth yield estimates from thermodynamics and its importance for degradation of pesticides and formation of biogenic non-extractable residues

In biodegradation studies with isotope-labelled pesticides, fractions of non-extractable residues (NER) remain, but their nature and composition is rarely known, leading to uncertainty about their risk. Microbial growth leads to incorporation of carbon into the microbial mass, resulting in biogenic NER. Formation of microbial mass can be estimated from the microbial growth yield, but experimental data is rare. Instead, we suggest using prediction methods for the theoretical yield based on thermodynamics. Recently, we presented the Microbial Turnover to Biomass (MTB) method that needs a minimum of input data. We have estimated the growth yield of 40 organic chemicals (31 pesticides) using the MTB and two existing methods. The results were compared to experimental values, and the sensitivity of the methods was assessed. The MTB method performed best for pesticides. Having the theoretical yield and using the released CO2 as a measure for microbial activity, we predicted a range for the formation of biogenic NER. For the majority of the pesticides, a considerable fraction of the NER was estimated to be biogenic. This novel approach provides a theoretical foundation applicable to the evaluation and prediction of biogenic NER formation during pesticide degradation experiments, and may also be employed for the interpretation of NER data from regulatory studies.

基質誘導呼吸(SIR)法による微生物活性の測定

基質誘導呼吸(SIR)法による微生物活性の測定

Changes in substrate availability drive carbon cycle response to chronic warming

As earth's climate continues to warm, it is important to understand how the capacity of terrestrial ecosystems to retain carbon (C) will be affected. We combined measurements of microbial activity with the concentration, quality, and physical accessibility of soil carbon to microorganisms to evaluate the mechanisms by which more than two decades of experimental warming has altered the carbon cycle in a Northeast US temperate deciduous forest. We found that concentrations of soil organic matter were reduced in both the organic and mineral soil horizons. The molecular composition of the carbon was altered in the mineral soil with significant reductions in the relative abundance of polysaccharides and lignin, and an increase in lipids. Mineral-associated organic matter was preferentially depleted by warming in the top 3 cm of mineral soil. We found that potential extracellular enzyme activity per gram of soil at a common temperature was generally unaffected by warming treatment. However, by measuring potential extracellular enzyme activities between 4 and 30 °C, we found that activity per unit microbial biomass at in-situ temperatures was increased by warming. This was associated with a tendency for microbial biomass to decrease with warming. These results indicate that chronic warming has reduced soil organic matter concentrations, selecting for a smaller but more active microbial community increasingly dependent on mineral-associated organic matter.

Anode potential influences the structure and function of anodic electrode and electrolyte-associated microbiomes.

Three bioelectrochemical systems were operated with set anode potentials of +300 mV, +550 mV and +800 mV vs. Standard Hydrogen Electrode (SHE) to test the hypothesis that anode potential influences microbial diversity and is positively associated with microbial biomass and activity. Bacterial and archaeal diversity was characterized using 16 S rRNA gene amplicon sequencing, and biofilm thickness was measured as a proxy for biomass. Current production and substrate utilization patterns were used as measures of microbial activity and the mid-point potentials of putative terminal oxidases were assessed using cyclic voltammetry. All measurements were performed after 4, 16, 23, 30 and 38 days. Microbial biomass and activity differed significantly between anode potentials and were lower at the highest potential. Anodic electrode and electrolyte associated community composition was also significantly influenced by anode potential. While biofilms at +800 mV were thinner, transferred less charge and oxidized less substrate than those at lower potentials, they were also associated with putative terminal oxidases with higher mid-point potentials and generated more biomass per unit charge. This indicates that microbes at +800 mV were unable to capitalize on the potential for additional energy gain due to a lack of adaptive traits to high potential solid electron acceptors and/or sensitivity to oxidative stress.

A decadal-scale nutrient loading study in a coastal wetland: Impacts on soil microbial processes

Fertilizer use in agricultural lands and treated wastewater disposal have increased bioavailable nitrogen (N) and phosphorus (P) loading to wetlands and aquatic systems with potential implications for nutrient cycling and soil microbial processes. Recently, conflicting results of N loading impacts on microbial-mediated organic matter decomposition in coastal wetland soils have been reported. However, to date, the majority of studies have investigated short-term nutrient loading effects while few have reported long-term integrated impacts. Here, we present results from an 11-year soil nutrient loading study in an oligohaline coastal wetland treated with 0, 50, 200, or 1200kgNha−1yr−1 in combination with 0 or 131kgPha−1yr−1. We measured soil (0–10cm) physiochemical characteristics, soil microbial biomass N, and measures of biogeochemical cycling of N, including potentially mineralizable nitrogen and denitrification rates. Our results show that soil total P increased with P additions, but no significant differences in measures of soil microbial biomass or activity occurred with N, P, or N×P loading. We conclude that long-term N loading at rates equivalent to Mississippi River diversions had no persistent lasting effects on total N or examined soil microbial measures.

Soil carbon characterization and nutrient ratios across land uses on two contrasting soils: Their relationships to microbial biomass and function

Soil carbon (C) plays a central role in the global biogeochemical cycles of most major nutrients, but the degree to which the quality versus quantity of C controls microbial abundance and function across land uses is still somewhat uncertain. We measured soil organic matter (SOM) concentration and composition as well as nutrient ratios and other soil characteristics on two contrasting soil types across three land uses (forest, pasture, maize cropping), to determine their relationships to microbial abundance and specific measures of microbial activity (e.g. qCO2, the ratio of respiration rate to microbial biomass, and net laboratory N mineralization). Although there was significant variability in bulk SOM composition (by 13C NMR spectroscopy), we could detect differences between broad-leaved forest and pasture/maize systems on a landscape scale, primarily attributable to differences in aryl C content. Variability in O-alkyl C between sites correlated strongly with the soil C:N ratio, but variability in alkyl C (which was particularly evident in pasture sites) could not be adequately explained by measured environmental or soil characteristics. Soil C:P and N:P ratios followed similar patterns with forest > pasture > maize. Bulk soil C:N, hot-water extractable C:N and particulate C:N all followed similar patterns with forest > pasture ≈ maize cropping. Microbial biomass C:N followed a different pattern, however, with forest ≈ pasture > maize. Despite the differences in SOM composition and nutrient ratios, anaerobically mineralizable N and hot-water extractable C (as a measures of available C) best explained the variation in microbial biomass and function across sites. Anaerobically mineralizable N generally explained the most variation for microbial biomass and qCO2 and had the smallest soil or land use effect. Hot-water extractable C explained the most variance for net N mineralization. Addition of stoichiometric measures and other soil attributes (e.g. soil C:N, C:P, δ15N) in a multiple regression model explained more of the variation than a single factor plus the land use effect (though soil order still explained a small, but significant amount of variance for measures of microbial biomass). A measure of available C, however, was needed to explain the maximum amount of variance in microbial biomass and function across sites (i.e. total C plus nutrient status and other soil attributes could not explain as much of the variance). Our data suggest that nutrient content/stoichiometry does assist in defining the quality of SOM, but a measure of available C (similar to the “active” pool in C models) is also needed. Anaerobically mineralizable N and/or hot water–water extractable C appear to be adequate measures of available C that relate to “active” C, but C functional groups (from 13C NMR spectroscopy) were not particularly useful for this purpose.

Spatial Analysis and Modeling the Nitrogen Flush after Rainfall Events at the Field Scale in SWAT

Current nitrogen (N) models tend to neglect the contribution of the microbial population to the plant available N pool, resulting in an underestimation of yield and possible over or underestimation of N runoff from natural and agricultural landscapes. We used the measurement of microbial activity coupled with the measurement of their food source, water extractable N and carbon (C), to provide initial N values and mineralization rates to modify N cycling in the Soil Water Assessment Tool (SWAT). Soil test data and spatial analysis of N mineralization values were used to: (1) quantify spatial variation of water extractable organic and inorganic N, soil inorganic N, and microbial activity; (2) develop a field scale model to determine N mineralization using updated soil testing methods for integration into the SWAT model; and (3) predict wheat yield. Simulation results indicate that yearly yield values and the variability of these yield values were consistently greater from the modified N model than from the SWAT model, as would be expected with the addition of N mineralization resulting from microbial activity. The spatial variability in yield results by sample increased with the modified N model as compared to the SWAT model. The yield data resulting from the modified N model simulation were sensitive to soil nutrient values as well as variation in elevation. Temporal and climatic variability is accounted for by including a precipitation trigger for N mineralization. The equations used to model the complex biogeochemical N cycling relationships are elegant in their simplicity, yet capture the spatial complexity associated with their processes. The modified N model may be useful to regulators to help with the simulation of new conservation practices that include the effect of lower fertilizer inputs on nutrient runoff and pollution.

An evaluation of cellobiose as an alternative reference substance for isothermal microcalorimetry measurements of soil microbial activity

Cellobiose biodegradation in soil samples containing different doses of phosphogypsum was investigated by isothermal microcalorimetry. The results were compared with glucose biodegradation data in identical soil samples. A similar tendency was observed in cellobiose and glucose biodegradation processes. The rate of decomposition of the analyzed saccharides decreased with a rise in phosphogypsum doses in soil samples. During cellobiose and glucose biodegradation, the rate of heat production and the apparent growth rate constant decreased, whereas peak time and generation time increased with a rise in the phosphogypsum content of the investigated soil samples. The heat of cellobiose and glucose biodegradation increased in response to higher phosphogypsum doses in the soil.

Coupling of bacterial nitrification with denitrification and anammox supports N removal in intertidal sediments (Arcachon Bay, France)

Microbial activity measurements and molecular approaches were combined to study temporal variation in nitrogen (N) removal mechanisms from muddy and sandy intertidal sediments (Arcachon Bay, France). Stable isotopes (15NH4+/15NO3-) were used to measure oxidation of NH4+ to NO3−/NO2- and its subsequent reduction to N2 via denitrification and/or anammox. We found that denitrification mainly fuelled N loss in both sediment types. However in sandy sediments, anammox accounted for relatively higher N2 production (45%). Nitrification–denitrification (Dn) and nitrification–anammox coupling was observed particularly in muddy sediments. Temporal variations in prokaryotic abundance (Bacteria, Archaea) and of functional groups responsible for nitrification and denitrification were studied by qPCR and for anammoxifiers by cloning. Bacterial density in both sediment types varied between 107−8 equivalent cell per g−1 dry weight sediment and were overall more abundant in muddy sediments. Archaeal equivalent cell varied between 0.5 and 6.5% of the total prokaryotes, with extreme values observed in muddy sediment during October and January respectively. Denitrifiers were 1–2 orders higher than ammonium oxidizers and archeal nitrifiers appeared insignificant compared to betaproteobacterial counterpart. Furthermore, nitrifiers exhibited greater fluctuations in sandy sediments compared to muddy ones. Anammoxifiers were mainly restricted to the “Candidatus Scalindua” group, and were detected in both sediment types and all sampling periods providing an indirect proof on the occurrence of anammox. In muddy sediments, N2 production presented overall higher rate over sandy sediments and exhibited the same trend as nitrifier abundance. This finding suggests a central role of bacterially-mediated benthic nitrification in supporting dissimilatory processes through generation of NO3−/NO2 and preventing eutrophication in this mesotidal lagoon.

Activity and interactions of methane seep microorganisms assessed by parallel transcription and FISH-NanoSIMS analyses.

To characterize the activity and interactions of methanotrophic archaea (ANME) and Deltaproteobacteria at a methane-seeping mud volcano, we used two complimentary measures of microbial activity: a community-level analysis of the transcription of four genes (16S rRNA, methyl coenzyme M reductase A (mcrA), adenosine-5′-phosphosulfate reductase α-subunit (aprA), dinitrogenase reductase (nifH)), and a single-cell-level analysis of anabolic activity using fluorescence in situ hybridization coupled to nanoscale secondary ion mass spectrometry (FISH-NanoSIMS). Transcript analysis revealed that members of the deltaproteobacterial groups Desulfosarcina/Desulfococcus (DSS) and Desulfobulbaceae (DSB) exhibit increased rRNA expression in incubations with methane, suggestive of ANME-coupled activity. Direct analysis of anabolic activity in DSS cells in consortia with ANME by FISH-NanoSIMS confirmed their dependence on methanotrophy, with no 15NH4+ assimilation detected without methane. In contrast, DSS and DSB cells found physically independent of ANME (i.e., single cells) were anabolically active in incubations both with and without methane. These single cells therefore comprise an active ‘free-living' population, and are not dependent on methane or ANME activity. We investigated the possibility of N2 fixation by seep Deltaproteobacteria and detected nifH transcripts closely related to those of cultured diazotrophic Deltaproteobacteria. However, nifH expression was methane-dependent. 15N2 incorporation was not observed in single DSS cells, but was detected in single DSB cells. Interestingly, 15N2 incorporation in single DSB cells was methane-dependent, raising the possibility that DSB cells acquired reduced 15N products from diazotrophic ANME while spatially coupled, and then subsequently dissociated. With this combined data set we address several outstanding questions in methane seep microbial ecosystems and highlight the benefit of measuring microbial activity in the context of spatial associations.

Methane Gas Reduction Using Virgin Coconut Oil Supplementation in Rumen Fermentation through in Vitro

This study aims to determine the effect of virgin coconut oil (VCO)supplementation into ruminant feed on the methane reduction in vitro The study used rumen fluid with forage substrate and concentrates in the ratio of 60:40. The experiement consists of five kinds of VCO treatments, namely: R0 – feed substrates without VCO; R1 – feed substrates with 2% VCO; R2 – feed substrates with 4% VCO; R3 – feed substrates with 6% VCO; and R4 – feed substrates with 8% VCO. Each treatment was done three times. The fermentation used Hohenheim Gas Test (HGT) at a temperature of 390 C for 48 hours. At the end of the fermentation, measurements of methane and microbial activity of the rumen fluid were implemented. Data obtained were analyzed using a completely randomized design, and continued with Duncan test for examining the mean differences. The results showed that methane production descreased by 18.39% - 29.7% when the feed was given 2% - 8% VCO. Based in the findings, it can be concluded that the supplementation of 2% - 8% VCO can be used a substrate for ruminant feed because it can reduce methane and does not interfere the microbial activity of the fermentation of rumen fluid through in vitro.

Methane Gas Reduction Using Virgin Coconut Oil Supplementation in Rumen Fermentation through in Vitro

This study aims to determine the effect of virgin coconut oil (VCO)supplementation into ruminant feed on the methane reduction in vitro The study used rumen fluid with forage substrate and concentrates in the ratio of 60:40. The experiement consists of five kinds of VCO treatments, namely: R0 – feed substrates without VCO; R1 – feed substrates with 2% VCO; R2 – feed substrates with 4% VCO; R3 – feed substrates with 6% VCO; and R4 – feed substrates with 8% VCO. Each treatment was done three times. The fermentation used Hohenheim Gas Test (HGT) at a temperature of 390 C for 48 hours. At the end of the fermentation, measurements of methane and microbial activity of the rumen fluid were implemented. Data obtained were analyzed using a completely randomized design, and continued with Duncan test for examining the mean differences. The results showed that methane production descreased by 18.39% - 29.7% when the feed was given 2% - 8% VCO. Based in the findings, it can be concluded that the supplementation of 2% - 8% VCO can be used a substrate for ruminant feed because it can reduce methane and does not interfere the microbial activity of the fermentation of rumen fluid through in vitro.

A Lixisol Microbial Activity Under Urban Wastes Composts Effect in Donsin, Burkina Faso

Mineralization causes soil carbon loss. This study focuses soil microbial activity measurement in relation with the application of six types of composts in sorghum three-year experiment. Composts were applied single or combined with urea. Organic carbon content, microbial biomass, respirometry and carbon global mineralization rate were evaluated. In comparison to the control, single composts treatments parameters variation rates ranged from -1 to +71%. When composts were combined with urea, parameters variations rates ranged from -8 to +107%. Under single urea, these parameters variation rates ranged from -14% to +31%. Best composts seemed to be those produced with various and balanced composting materials. Eco-friendly composts adoption could improve soil organic carbon content for sustainable microbial process. Keywords : Agro systems; carbon; respirometry; Burkina Faso.

Soil ecotoxicity assessment of glyphosate use under field conditions: microbial activity and community structure of Eubacteria and ammonia-oxidising bacteria.

A plot-scale experiment was conducted to assess the impact of field application rates of glyphosate on soil microbial communities by taking measurements of microbial activity (in terms of substrate-induced respiration and enzyme activity) in parallel with culture-independent approaches to assessing both bacterial abundance and diversity. Two rates of glyphosate, alone or in a mixture with 2,4-dichlorophenoxyacetic acid, were applied directly onto the soil surface, simulating normal use in chemical fallow in no-till systems. No consistent rate-dependent responses were observed in the microbial activity parameters investigated in the field plots that were exposed to glyphosate. Denaturant gradient gel electrophoresis (DGGE) of the overall bacterial community (Eubacteria) and ammonia-oxidising bacteria (AOB) revealed no effects of the high rate of glyphosate on the structure of the communities in comparison with the control. No treatment effects were observed on the abundance of Eubacteria shortly after treatment in 2010, while a small but significant difference between the high rate and the control was detected in the first sampling in 2011. The abundance of AOB was relatively low during the study, and treatment effects were undetectable. The absence of negative effects on soil microbial communities in this study suggests that glyphosate use at recommended rates poses low risk to the microbiota.

Delayed settling of marine snow: Effects of density gradient and particle properties and implications for carbon cycling

Marine snow aggregates are often a dominant component of carbon flux and are sites of high bacterial activity; thus, small-scale changes in the settling behavior of marine snow can affect the vertical locations of carbon export and remineralization in the surface ocean. In this study, we experimentally investigated the sinking velocities of marine snow aggregates formed in roller tanks as they settled through sharp density gradients. We observed between 8 and 10 aggregates in 3 different experiments, each of which displayed delayed settling behavior — that is, a settling velocity minimum — as they crossed the density transitions. Characteristics of delayed settling behavior were also compared to density stratification and aggregate density and size; aggregate settling velocity decreased more, and for longer periods of time, when density gradients were sharper and when aggregates were less dense. The observed relationships between non-dimensional parameters and aggregate settling allow for direct application of our results to the field, providing insight into the conditions under which strong delayed settling behavior is likely to occur. Activities of extracellular enzymes (the initial step in microbial remineralization of organic matter) were more than an order of magnitude higher in the aggregates compared to the surrounding water from which the aggregates were derived. Coupling measured enzyme activities with observations of delayed settling behavior demonstrates that the extent as well as the vertical location of enzyme activity is strongly affected by aggregate settling behavior: total enzyme activity within the region of the density transition increased by a factor of 18 with increasing stratification. This study, which combines direct measurements of small-scale aggregate settling and microbial enzyme activity, offers an opportunity to determine the potential implications of delayed settling behavior for local and larger-scale carbon cycling in the ocean.

Root expression of nitrogen metabolism genes reflects soil nitrogen cycling in an organic agroecosystem

Background and aims Roots in agroecosystems encounter spatiallyand temporallyheterogeneous nitrogen (N) availability in soil. Understanding root physiological processes in concert with soil microbial N dynamics following spatially discrete N pulses under field conditions will aid in the management of agroecosystem processes for N use efficiency. Methods This study examined the short-term response (<5 days) of tomato (Solanum lycopersicum L.) roots and soil N cycling to a pulse of inorganic N in an undisturbed soil patch on an organic farm using a novel combination of molecular and 15 N isotopic techniques. Results Tomato roots rapidly responded to and exploited the N pulse via upregulation of key N metabolism genes (e.g. cytosolic glutamine synthetase GS1) that comprise the core physiological response of roots to patchy soil N availability. Strong root activity limited accumulation of soil NO3 − despite high rates of gross nitrification. Roots out-competed soil microbes for the inorganic N, even on a short time scale, likely as a result of high plant N demand and microbial C limitation. The transient root gene expression response (absent by 4 days after the N pulse) underscored the sensitivity of root N uptake to local N availability. Conclusions Root expression of genes such as GS1 could complement soil inorganic N pools and measurements of soil microbial activity to serve as integrative indicators of rapid plant-soil N cycling.

Soil extracellular enzyme activities are sensitive indicators of detrital inputs and carbon availability

In a litter manipulation experiment in a temperate deciduous oak forest in Central Europe, we examined soil carbon contents and density fractions, as well as β-glucosidase and polyphenol oxidase enzyme activities, which play central roles in the degradation of litter and soil organic matter. Our measurements were taken in the DIRT (detritus input and removal treatments) plots, where manipulations include doubling of leaf litter or woody debris inputs, as well as removal of litter, trenching to prevent root inputs, and removal of all litter inputs. After 10 years of manipulation, soil C content did not vary predictably among plots, although the amount of light fraction material was greater in control and litter addition plots compared to litter removal plots. Even after 10 years of litter addition, there were no significant differences in activities of either enzyme in double litter plots compared to control plots, a result consistent with other observed measures of microbial activity. However, removal of roots and litter caused significant decreases in β-glucosidase activities very quickly, and these differences increased over time. However, polyphenol oxidase activities were not significant different among treatments. Enzyme activities were not correlated with total soil carbon contents, but activities of both enzymes were significantly and positively related to the amount of light fraction carbon, suggesting that enzymes respond to increases in labile carbon availability.

Can Changes in Soil Properties in Organic Banana Production Suppress Fusarium Wilt?

Organic agriculture promotes disease suppression through healthy soils by increasing biological activity and diversity through the application of organic fertilizers and increasing organic inputs. Fusarium wilt of bananas (Fusarium oxysporum f. sp. Fcubense) (Foc), also known as Panama disease, has been a devastating disease throughout the world. So far, no fungicides or cultural measures have been found that control Foc sufficiently. The aim of this research was to assess whether organic-based farming systems were more resilient than inorganic farming systems to soil borne diseases, in particular Fusarium wilts. A survey was conducted comparing five organic and five conventional banana plantations at paired sites in north Queensland, Australia. Soil samples were collected and analysed for chemical, physical and biological soil health indicators. Disease development of F. oxysporum f. sp. lycopersici in tomatoes and Foc in bananas were studied in pot trials to pursue clues for identifying Fusarium suppressive soil traits. Organic soils from the survey showed higher microbial activity and lower disease symptom expression (both with tomatoes and bananas) than conventional soils. In the survey, nematode diversity and soil sulphate content were recurring indicators in all experiments showing close correlations to pathogen growth, disease expression and plant health. Organic soils were lower in plant-parasitic nematodes and sulphate sulphur levels and higher in nematode diversity, labile soil C and microbial indicators. Soil conduciveness or suppression of Foc appeared to be largely governed by competition for carbon. Measurement of soil microbial enzyme activity, nematode community structure and diversity and possibly sulphate sulphur seem to provide a relatively reliable indicator for general disease suppression. Differences between organic and conventional agriculture cannot be related to single management practices, but may be linked to synergies among system components.

C mineralization and microbial activity in four biochar field experiments several years after incorporation

Most studies looking into the effect of amendment of biochar on soil microbial functioning employ short-term laboratory studies and probably describe relatively transient phenomena. Multi-year experiments, spanning beyond initial degradation of biologically labile biochar constituents, on the other hand are more scarce, although these are much needed to establish the medium-term effect of biochar on soil organisms. In the present study, soil was sampled from biochar-amended and control plots of four biochar field trials at Lincoln (UK), Rivignano, Rocca Bernarda and Beano in Italy. Air-dried pre-incubated soil samples were incubated at 15 °C for 8–9 weeks to follow-up carbon dioxide (CO2) emissions. We then determined soil β-glucosidase and dehydrogenase enzyme activity, and used PLFA analysis to quantify the total soil microbial biomass and community structure. The analysis indicated that soil microbial activity was either not affected or inhibited to different extents in the biochar-amended plots. At Lincoln, with the highest application rate (49 t ha−1), an overall inhibition of all investigated measures of microbial activity, a lower sum of extracted PLFAs and lower fungal abundance were observed. On the other end at Beano, depth dispersion of biochar by deep tillage and a lower application rate (20 t ha−1) probably explain the absence of any significant effect on microbial activity in that experiment. At Rivignano and Rocca Bernarda, dehydrogenase activity was lower in the biochar amended soil and C-mineralization was lower as well for Rivignano. Interestingly, however, β-glucosidase activity and the sum of extracted PLFAs was not affected by biochar treatment. Several mechanisms could reconcile the different effect of biochar application on overall microbial activity on the one hand and microbial abundance and rate of cellulose degradation on the other. Biochar amendment led to a lowered or equal soil microbial activity and abundance in most field sites. In contrast to many short-term laboratory studies, it therefore seems unlikely that biochar would still function as a substrate 1–4 years after incorporation in the field.

Effect of inoculum source on the enrichment of microbial communities on two lignocellulosic bioenergy crops under thermophilic and high-solids conditions.

Culturing compost-derived microbial communities on biofuel feedstocks under industrial conditions is a technique to enrich for organisms and lignocellulolytic enzymes for bioenergy feedstock deconstruction. In this study, microbial communities from green waste compost (GWC) and grape pomace compost (GPC) were cultured on switchgrass and eucalyptus to observe the impact of inoculation on feedstock decomposition and microbial community structure. Respiration was monitored as a measure of microbial activity, and 16S ribosomal RNA gene sequencing was used to characterize microbial community structure. The enriched community structure and respiration were influenced by the choice of feedstock, compost type, and application of thermophilic, high-solids conditions. However, the effect of compost source was significantly less than the effects of the other culture variables. Although there are subtle differences in potentially lignocellulolytic taxa between GPC- and GWC-derived communities, these differences do not affect the decomposition rates for these communities on switchgrass or eucalyptus. These results are useful for designing future experiments to discover lignocellulolytic micro-organisms from compost. They suggest that such work may be better served by deemphasizing screening of compost sources and instead focusing on how compost-derived communities adapt to the feedstocks and process conditions relevant to biofuel production.