A respiro-fermentative strategy to survive nanoxia in Acidobacterium capsulatum.

Microbial soil habitats are characterized by rapid shifts in substrate and nutrient availabilities, as well as chemical and physical parameters. One such parameter that can vary in soil is oxygen; thus, microbial survival is dependent on adaptation to this substrate. To better understand the metabolic abilities and adaptive strategies to oxygen-deprived environments, we combined genomics with transcriptomics of a model organism, Acidobacterium capsulatum, to explore the effect of decreasing, environmentally relevant oxygen concentrations.

Plant roots affect free-living diazotroph communities in temperate grassland soils despite decades of fertilization.

Fixation of atmospheric N by free-living diazotrophs accounts for an important proportion of nitrogen naturally introduced to temperate grasslands. The effect of plants or fertilization on the general microbial community has been extensively studied, yet an understanding of the potential combinatorial effects on the community structure and activity of free-living diazotrophs is lacking. In this study we provide a multilevel assessment of the single and interactive effects of different long-term fertilization treatments, plant species and vicinity to roots on the free-living diazotroph community in relation to the general microbial community in grassland soils.

Survival and rapid resuscitation permit limited productivity in desert microbial communities.

Microbial activity in drylands tends to be confined to rare and short periods of rain. Rapid growth should be key to the maintenance of ecosystem processes in such narrow activity windows, if desiccation and rehydration cause widespread cell death due to osmotic stress. Here, simulating rain with HO followed by single-cell NanoSIMS, we show that biocrust microbial communities in the Negev Desert are characterized by limited productivity, with median replication times of 6 to 19 days and restricted number of days allowing growth.

Reevaluation and novel insights into amino sugar and neutral sugar necromass biomarkers in archaea, bacteria, fungi, and plants.

Soil microbial necromass is an important contributor to soil organic matter (>50%) and it is largely composed of microbial residues. In soils, fragmented cell wall residues are mostly found in their polysaccharide forms of fungal chitin and bacterial peptidoglycan. Microbial necromass biomarkers, particularly amino sugars (AS) such as glucosamine (GlcN) and muramic acid (MurA) have been used to trace fungal and bacterial residues in soils, and to distinguish carbon (C) found in microbial residues from non-microbial organic C.

Microaerobic Lifestyle at Nanomolar O Concentrations Mediated by Low-Affinity Terminal Oxidases in Abundant Soil Bacteria.

High-affinity terminal oxidases (TOs) are believed to permit microbial respiration at low oxygen (O) levels. Genes encoding such oxidases are widespread, and their existence in microbial genomes is taken as an indicator for microaerobic respiration. We combined respiratory kinetics determined via highly sensitive optical trace O sensors, genomics, and transcriptomics to test the hypothesis that high-affinity TOs are a prerequisite to respire micro- and nanooxic concentrations of O in environmentally relevant model soil organisms: acidobacteria.

Acidobacteria are active and abundant members of diverse atmospheric H-oxidizing communities detected in temperate soils.

Significant rates of atmospheric dihydrogen (H) consumption have been observed in temperate soils due to the activity of high-affinity enzymes, such as the group 1h [NiFe]-hydrogenase. We designed broadly inclusive primers targeting the large subunit gene (hhyL) of group 1h [NiFe]-hydrogenases for long-read sequencing to explore its taxonomic distribution across soils. This approach revealed a diverse collection of microorganisms harboring hhyL, including previously unknown groups and taxonomically not assignable sequences.

One Complete and Seven Draft Genome Sequences of Subdivision 1 and 3 Isolated from Soil.

We report eight genomes from representatives of the phylum subdivisions 1 and 3, isolated from soils. The genome sizes range from 4.9 to 6.

Soil multifunctionality is affected by the soil environment and by microbial community composition and diversity.

Microorganisms are critical in mediating carbon (C) and nitrogen (N) cycling processes in soils. Yet, it has long been debated whether the processes underlying biogeochemical cycles are affected by the composition and diversity of the soil microbial community or not. The composition and diversity of soil microbial communities can be influenced by various environmental factors, which in turn are known to impact biogeochemical processes.

Rapid Transfer of Plant Photosynthates to Soil Bacteria via Ectomycorrhizal Hyphae and Its Interaction With Nitrogen Availability.

Plant roots release recent photosynthates into the rhizosphere, accelerating decomposition of organic matter by saprotrophic soil microbes ("rhizosphere priming effect") which consequently increases nutrient availability for plants. However, about 90% of all higher plant species are mycorrhizal, transferring a significant fraction of their photosynthates directly to their fungal partners. Whether mycorrhizal fungi pass on plant-derived carbon (C) to bacteria in root-distant soil areas, i.

Evaluation of Primers Targeting the Diazotroph Functional Gene and Development of NifMAP - A Bioinformatics Pipeline for Analyzing Amplicon Data.

Diazotrophic microorganisms introduce biologically available nitrogen (N) to the global N cycle through the activity of the nitrogenase enzyme. The genetically conserved dinitrogenase reductase () gene is phylogenetically distributed across four clusters (I-IV) and is widely used as a marker gene for N fixation, permitting investigators to study the genetic diversity of diazotrophs in nature and target potential participants in N fixation. To date there have been limited, standardized pipelines for analyzing the functional gene, which is in stark contrast to the 16S rRNA gene.

Peatland Acidobacteria with a dissimilatory sulfur metabolism.

Sulfur-cycling microorganisms impact organic matter decomposition in wetlands and consequently greenhouse gas emissions from these globally relevant environments. However, their identities and physiological properties are largely unknown. By applying a functional metagenomics approach to an acidic peatland, we recovered draft genomes of seven novel Acidobacteria species with the potential for dissimilatory sulfite (dsrAB, dsrC, dsrD, dsrN, dsrT, dsrMKJOP) or sulfate respiration (sat, aprBA, qmoABC plus dsr genes).

Genomic insights into the Acidobacteria reveal strategies for their success in terrestrial environments.

Members of the phylum Acidobacteria are abundant and ubiquitous across soils. We performed a large-scale comparative genome analysis spanning subdivisions 1, 3, 4, 6, 8 and 23 (n = 24) with the goal to identify features to help explain their prevalence in soils and understand their ecophysiology. Our analysis revealed that bacteriophage integration events along with transposable and mobile elements influenced the structure and plasticity of these genomes.

A bacterial pioneer produces cellulase complexes that persist through community succession.

Cultivation of microbial consortia provides low-complexity communities that can serve as tractable models to understand community dynamics. Time-resolved metagenomics demonstrated that an aerobic cellulolytic consortium cultivated from compost exhibited community dynamics consistent with the definition of an endogenous heterotrophic succession. The genome of the proposed pioneer population, 'Candidatus Reconcilibacillus cellulovorans', possessed a gene cluster containing multidomain glycoside hydrolases (GHs).

Application of stable-isotope labelling techniques for the detection of active diazotrophs.

Investigating active participants in the fixation of dinitrogen gas is vital as N is often a limiting factor for primary production. Biological nitrogen fixation is performed by a diverse guild of bacteria and archaea (diazotrophs), which can be free-living or symbionts. Free-living diazotrophs are widely distributed in the environment, yet our knowledge about their identity and ecophysiology is still limited.

Refining the phylum Chlorobi by resolving the phylogeny and metabolic potential of the representative of a deeply branching, uncultivated lineage.

Recent studies have expanded the phylum Chlorobi, demonstrating that the green sulfur bacteria (GSB), the original cultured representatives of the phylum, are a part of a broader lineage whose members have more diverse metabolic capabilities that overlap with members of the phylum Bacteroidetes. The 16S rRNA gene of an uncultivated clone, OPB56, distantly related to the phyla Chlorobi and Bacteroidetes, was recovered from Obsidian Pool in Yellowstone National Park; however, the detailed phylogeny and function of OPB56 and related clones have remained unknown. Culturing of thermophilic bacterial consortia from compost by adaptation to grow on ionic-liquid pretreated switchgrass provided a consortium in which one of the most abundant members, NICIL-2, clustered with OPB56-related clones.

Advancements in the application of NanoSIMS and Raman microspectroscopy to investigate the activity of microbial cells in soils.

The combined approach of incubating environmental samples with stable isotope-labeled substrates followed by single-cell analyses through high-resolution secondary ion mass spectrometry (NanoSIMS) or Raman microspectroscopy provides insights into the in situ function of microorganisms. This approach has found limited application in soils presumably due to the dispersal of microbial cells in a large background of particles. We developed a pipeline for the efficient preparation of cell extracts from soils for subsequent single-cell methods by combining cell detachment with separation of cells and soil particles followed by cell concentration.

Substrate-Specific Development of Thermophilic Bacterial Consortia by Using Chemically Pretreated Switchgrass.

Microbial communities that deconstruct plant biomass have broad relevance in biofuel production and global carbon cycling. Biomass pretreatments reduce plant biomass recalcitrance for increased efficiency of enzymatic hydrolysis. We exploited these chemical pretreatments to study how thermophilic bacterial consortia adapt to deconstruct switchgrass (SG) biomass of various compositions.

Nitrogen fertilization has a stronger effect on soil nitrogen-fixing bacterial communities than elevated atmospheric CO2.

Biological nitrogen fixation is the primary supply of N to most ecosystems, yet there is considerable uncertainty about how N-fixing bacteria will respond to global change factors such as increasing atmospheric CO2 and N deposition. Using the nifH gene as a molecular marker, we studied how the community structure of N-fixing soil bacteria from temperate pine, aspen, and sweet gum stands and a brackish tidal marsh responded to multiyear elevated CO2 conditions. We also examined how N availability, specifically, N fertilization, interacted with elevated CO2 to affect these communities in the temperate pine forest.

Community dynamics of cellulose-adapted thermophilic bacterial consortia.

Enzymatic hydrolysis of cellulose is a key process in the global carbon cycle and the industrial conversion of biomass to biofuels. In natural environments, cellulose hydrolysis is predominately performed by microbial communities. However, detailed understanding of bacterial cellulose hydrolysis is primarily confined to a few model isolates.

A robust PCR primer design platform applied to the detection of Acidobacteria Group 1 in soil.

Environmental biosurveillance and microbial ecology studies use PCR-based assays to detect and quantify microbial taxa and gene sequences within a complex background of microorganisms. However, the fragmentary nature and growing quantity of DNA-sequence data make group-specific assay design challenging. We solved this problem by developing a software platform that enables PCR-assay design at an unprecedented scale.

Identification of cellulose-responsive bacterial and fungal communities in geographically and edaphically different soils by using stable isotope probing.

Many bacteria and fungi are known to degrade cellulose in culture, but their combined response to cellulose in different soils is unknown. Replicate soil microcosms amended with [(13)C]cellulose were used to identify bacterial and fungal communities responsive to cellulose in five geographically and edaphically different soils. The diversity and composition of the cellulose-responsive communities were assessed by DNA-stable isotope probing combined with Sanger sequencing of small-subunit and large-subunit rRNA genes for the bacterial and fungal communities, respectively.

Common bacterial responses in six ecosystems exposed to 10 years of elevated atmospheric carbon dioxide.

Six terrestrial ecosystems in the USA were exposed to elevated atmospheric CO(2) in single or multifactorial experiments for more than a decade to assess potential impacts. We retrospectively assessed soil bacterial community responses in all six-field experiments and found ecosystem-specific and common patterns of soil bacterial community response to elevated CO(2) . Soil bacterial composition differed greatly across the six ecosystems.

Accurate, rapid taxonomic classification of fungal large-subunit rRNA genes.

Taxonomic and phylogenetic fingerprinting based on sequence analysis of gene fragments from the large-subunit rRNA (LSU) gene or the internal transcribed spacer (ITS) region is becoming an integral part of fungal classification. The lack of an accurate and robust classification tool trained by a validated sequence database for taxonomic placement of fungal LSU genes is a severe limitation in taxonomic analysis of fungal isolates or large data sets obtained from environmental surveys. Using a hand-curated set of 8,506 fungal LSU gene fragments, we determined the performance characteristics of a naïve Bayesian classifier across multiple taxonomic levels and compared the classifier performance to that of a sequence similarity-based (BLASTN) approach.