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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Deconstruction by C. thermocellum —from microbe mediated to dynamic redistribution of cellulosomes

Clostridium thermocellum is one of the most efficient microorganisms for the deconstruction of cellulosic biomass. To achieve this high level of cellulolytic activity, C. thermocellum uses large multienzyme complexes known as cellulosomes to break down complex polysaccharides, notably cellulose, found in plant cell walls. The attachment of bacterial cells to the nearby substrate via the cellulosome has been hypothesized to be the reason for this high efficiency. The region lying between the cell and the substrate has shown great variation and dynamics that are affected by the growth stage of cells and the substrate used for growth. Here, we used both super-resolution imaging and machine-learning approaches to study the distribution of C. thermocellum cellulosomes at different stages of growth. We show that C. thermocellum initially retains its cellulosomes primarily on the cell surface but then relocates large cellulosome clusters to the interface with biomass, therefore depleting its cell surface of cellulosomes. These results indicate dynamic redistribution of cellulosomes during growth, with a functional shift toward substrate-associated degradation later during growth on biomass.

09 BIOMASS FUELS↗
DOE OSTI2020

Soil Microbes Trade-Off Biogeochemical Cycling for Stress Tolerance Traits in Response to Year-Round Climate Change

Winter air temperatures are rising faster than summer air temperatures in high-latitude forests, increasing the frequency of soil freeze/thaw events in winter. To determine how climate warming and soil freeze/thaw cycles affect soil microbial communities and the ecosystem processes they drive, we leveraged the Climate Change across Seasons Experiment (CCASE) at the Hubbard Brook Experimental Forest in the northeastern United States, where replicate field plots receive one of three climate treatments: warming (+5°C above ambient in the growing season), warming in the growing season + winter freeze/thaw cycles (+5°C above ambient +4 freeze/thaw cycles during winter), and no treatment. Soil samples were taken from plots at six time points throughout the growing season and subjected to amplicon (rDNA) and metagenome sequencing. We found that soil fungal and bacterial community composition were affected by changes in soil temperature, where the taxonomic composition of microbial communities shifted more with the combination of growing-season warming and increased frequency of soil freeze/thaw cycles in winter than with warming alone. Warming increased the relative abundance of brown rot fungi and plant pathogens but decreased that of arbuscular mycorrhizal fungi, all of which recovered under combined growing-season warming and soil freeze/thaw cycles in winter. The abundance of animal parasites increased significantly under combined warming and freeze/thaw cycles. We also found that warming and soil freeze/thaw cycles suppressed bacterial taxa with the genetic potential for carbon (i.e., cellulose) decomposition and soil nitrogen cycling, such as N fixation and the final steps of denitrification. These new soil communities had higher genetic capacity for stress tolerance and lower genetic capacity to grow or reproduce, relative to the communities exposed to warming in the growing season alone. Our observations suggest that initial suppression of biogeochemical cycling with year-round climate change may be linked to the emergence of taxa that trade-off growth for stress tolerance traits.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Culturing of “Unculturable” Subsurface Microbes: Natural Organic Carbon Source Fuels the Growth of Diverse and Distinct Bacteria From Groundwater

Recovery and cultivation of diverse environmentally-relevant microorganisms from the terrestrial subsurface remain a challenge despite recent advances in modern molecular technology. Here, we applied complex carbon (C) sources, i.e., sediment dissolved organic matter (DOM) and bacterial cell lysate, to enrich groundwater microbial communities for 30 days. As comparisons, we also included enrichments amended with simple C sources including glucose, acetate, benzoate, oleic acid, cellulose, and mixed vitamins. Our results demonstrate that complex C is far more effective in enriching diverse and distinct microorganisms from groundwater than simple C. Simple C enrichments yield significantly lower biodiversity, and are dominated by few phyla (e.g., Proteobacteria and Bacteroidetes ), while microcosms enriched with complex C demonstrate significantly higher biodiversity including phyla that are poorly represented in published culture collections (e.g., Verrucomicrobia , Planctomycetes , and Armatimonadetes ). Subsequent isolation from complex C enrichments yielded 228 bacterial isolates representing five phyla, 17 orders, and 56 distinct species, including candidate novel, rarely cultivated, and undescribed organisms. Results from this study will substantially advance cultivation and isolation strategies for recovering diverse and novel subsurface microorganisms. Obtaining axenic representatives of “once-unculturable” microorganisms will enhance our understanding of microbial physiology and function in different biogeochemical niches of terrestrial subsurface ecosystems.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Enhancement on selenium volatilization for phytoremediation: role of plant and soil microbe interaction

This study aimed at quantifying the potential effects of plant and soil microbial interaction on selenium (Se) volatilization, with the specific objectives of identifying soil bacteria associated with rabbitfoot grass (Polypogon monspeliensis) and demonstrating the enhancement of Se volatilization in the soil-Indian mustard (Brassica juncea) system through inoculation of the soil with the identified best Se-volatilizing bacterial strain. Soil bacteria were isolated from topsoil and rhizosphere soils of rabbitfoot grass, and the bacterial colonies were characterized via PCR-DGGE and DGGE band analysis prior to their identification using 16S rDNA sequencing technique.Bacillus cereusproduced over 500-fold more volatile Se in a culture medium treated with 15 µg Se/mL (equal mixture of SeO 4 2- , SeO 3 2- and selenomethionine) than any of the other eight identified bacterial strains. Inoculation of Indian mustard vegetated soil with the best Se volatilizing bacterial strainB. cereusresulted in a significant (p<0.05) increase in Se volatilization during a 7-day time period, compared to the soil-plant system without inoculation ofB. cereus. Thus, inoculation of the soil withB. cereussubstantially enhanced Se removal via biogenic volatilization in the soil-Indian mustard system. This study evaluated the role ofB. cereusin enhancing Se volatilization in soil-plant systems, and demonstrated the importance of plant and soil microbial interaction for Se phytoremediation.

Plant Sciences↗
DOE OSTI2021

Disturbance triggers non-linear microbe–environment feedbacks

Abstract. Conceptual frameworks linking microbial community membership, properties, and processes with the environment and emergent function have been proposed but remain untested. Here we refine and test a recent conceptual framework using hyporheic zone sediments exposed to wetting–drying transitions. Our refined framework includes relationships between cumulative properties of a microbial community (e.g., microbial membership, community assembly properties, and biogeochemical rates), environmental features (e.g., organic matter thermodynamics), and emergent ecosystem function. Our primary aim was to evaluate the hypothesized relationships that comprise the conceptual framework and contrast outcomes from the whole and putatively active bacterial and archaeal communities. Throughout the system we found threshold-like responses to the duration of desiccation. Membership of the putatively active community – but not the whole bacterial and archaeal community – responded due to enhanced deterministic selection (an emergent community property). Concurrently, the thermodynamic properties of organic matter (OM) became less favorable for oxidation (an environmental component), and respiration decreased (a microbial process). While these responses were step functions of desiccation, we found that in deterministically assembled active communities, respiration was lower and thermodynamic properties of OM were less favorable. Placing the results in context of our conceptual framework points to previously unrecognized internal feedbacks that are initiated by disturbance and mediated by thermodynamics and that cause the impacts of disturbance to be dependent on the history of disturbance.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Characterizing intracellular proteomes for microbes: An experimental approach using label-free protein quantitation

Genomic and transcriptomic studies generate a rich source of molecular information; however, neither a static genome nor the presence of a messenger RNA provides the most direct insight into the functional state of a microbial cell at any given time. Rather, it is the ensemble of proteins (i.e., proteome) that is the primary workhorse for most biological processes that are concurrent and coordinately active in a living cell. Currently, mass-spectrometry-based (MS) technologies provide unprecedented information into the composition of the proteome, shedding light on the numerous complex biological processes actively shaping observed phenotypes. Herein, we detail a protocol for the exploration of intracellular proteomes through the large-scale, unbiased identification of proteins and their relative abundances using liquid chromatography (LC) coupled to tandem mass spectrometry (MS/MS). In general, this protocol is applicable to both microbial and eukaryotic systems.

Abraham, Paul↗
DOE OSTI2020

Complex of mutualistic microbes designed to increase plant productivity

The present disclosure provides agricultural compositions and methods of using these compositions to increase plant growth, pathogen resistance and drought tolerance. The agricultural compositions disclosed herein comprise mixtures of mutualistic beneficial fungi such as Laccaria bicolor and Piriformispora indica, and bacterial strains of Pseudomonas.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Engineered microbes for conversion of organic compounds to medium chain length alcohols and methods of use

This disclosure provides a genetically-modified bacterium from the genus Pseudomonas that comprises an exogenous nucleic acid encoding an enoyl-CoA reductase and an exogenous nucleic acid encoding an acyl-CoA reductase that produces medium chain length alcohols. The disclosure further provides methods for producing medium chain alcohols using such genetically-modified bacterium. This disclosure provides a renewable, bio-based production platform for valuable mcl-alcohols that have a wide range of industrial applications. Current production of mcl-alcohols typically occurs through the hydrogenation of plant oils and waxes. This process leads to issues of deforestation and is largely unsustainable. Utilizing waste lignin streams as the carbon source provides a more sustainable feedstock that can be generated from plant waste like corn stover. Along with this, the use of lignin avoids competition with food resources as traditional starch and sugar feedstocks.

Guss, Adam M.↗
DOE OSTI2022

Ecosystem device for determining plant-microbe interactions

This disclosure provides systems, methods, and devices related to the study of ecological processes. In one aspect, a device includes a base, a substrate, and an enclosure. The substrate is in contact with a first surface of the base. The substrate and the base define a root chamber. The enclosure is in contact with a second surface of the base. The base and the enclosure define a growth chamber. The base defines a stem port connecting the root chamber and the growth chamber. The base further defines a first port in fluid communication with the root chamber and a second port in fluid communication with the root chamber. The device is operable to contain a plant, roots of the plant being in the root chamber, a stem of the plant passing through the stem port, and leaves of the plant being in the growth chamber.

Andeer, Peter↗
DOE OSTI2023

Complex of mutualistic microbes designed to increase plant productivity

The present disclosure provides agricultural compositions and methods of using these compositions to increase plant growth, pathogen resistance and drought tolerance. The agricultural compositions disclosed herein comprise mixtures of mutualistic beneficial fungi such as Laccaria bicolor and Piriformispora indica, and bacterial strains of Pseudomonas.

Labbe, Jessy L.↗