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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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42 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Assessing horizontal gene transfer in the rhizosphere of Brachypodium distachyon using fabricated ecosystems (EcoFABs)

ABSTRACT Horizontal gene transfer (HGT) is a major process by which genes are transferred between microbes in the rhizosphere. However, examining HGT remains challenging due to the complexity of mimicking conditions within the rhizosphere. Fabricated ecosystems (EcoFABs) have been used to investigate several complex processes in plant-associated environments. Here we show that EcoFABs are efficient tools to examine and measure HGT frequency in the rhizosphere. We provide the first demonstration of gene transfer via a triparental conjugation system in the Brachypodium distachyon rhizosphere in an EcoFAB using Pseudomonas putida KT2440 as both donor and recipient bacterial strain with the donor containing a mobilizable and non-self-transmissible plasmid. We observed that the frequency of plasmid transfer in the rhizosphere is potentially dependent on the plant developmental stage and the composition and amount of root exudates. The frequency of plasmid transfer also increased with higher numbers of donor cells. We demonstrate the transfer of plasmid from P. putida to another B. distachyon root colonizer, Burkholderia sp. OAS925, showing HGT within a rhizosphere microbial community. Environmental stresses also influenced the rate and efficiency of HGT in the rhizosphere between different species and genera. This study provides a robust workflow to evaluate transfer of engineered plasmids in the rhizosphere when such plasmids are potentially introduced in a field or other plant-associated environments. IMPORTANCE We report the use of EcoFABs to investigate the HGT process in a rhizosphere environment. It highlights the potential of EcoFABs in recapitulating the dynamic rhizosphere conditions as well as their versatility in studying plant-microbe interactions. This study also emphasizes the importance of studying the parameters impacting the HGT frequency. Several factors such as plant developmental stages, nutrient conditions, number of donor cells, and environmental stresses influence gene transfer within the rhizosphere microbial community. This study paves the way for future investigations into understanding the fate and movement of engineered plasmids in a field environment.

Priya, Shweta↗
DOE OSTI2020

Diversified Therapeutic Phage Cocktails from Close Relatives of the Target Bacterium

This project tackles the antibiotic resistance crisis, developing a new method for discovering numerous efficacious bacteriophages for therapeutic cocktails against bacterial pathogens. The phage therapy approach to infectious disease, recently rekindled in U.S. medicine, requires numerous phages for each bacterial pathogen. Our approach 1) uses Sandia-unique software to identify dormant phages (prophages) integrated into bacterial chromosomes, 2) identifies prophage-laden bacteria that are close relatives of the target pathogenic strain to be killed, and 3) engineers away properties of these phages that are undesirable for therapy. We have perfected our phage-finding software, implemented our phage therapy strategy by targeting the pathogen Pseudomonas aeruginosa, and prepared new software to assist the phage engineering. We then turned toward Burkholderia pathogens, aiming to overcome the difficulty to transform these bacteria with a novel phage conjugation approach. Our work demonstrates the validity of a new approach to phage therapy for killing antibiotic resistant pathogens.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

3D, Real-time Label-free Visualization of Cellular Health

This work directly addresses a key question raised in TA7, Topic L1 of HDTRA1-16-24-FRCWMDCall, “Can quantum level changes be detected, mapped, and understood in the biological environment to allow faster diagnostic responses?” This work will use the inherently sensitive quantum property of a molecular excited state lifetime to visualize and map discrete, subtle nanometer-scale changes (e.g. NADPH vs NADH) that are key indicators of cellular health in response to chemical and biological threats and MCMs. It will also develop and exploit new, fast imaging light-sheet methods to allow faster diagnostic responses. This new imaging system will exploit time-correlated single photon counting and new advances in single-objective light-sheet microscopy (oblique plane microscopy) for fast, quantitative analysis of cellular redox state. We will add an entirely new dimension (excited state fluorescence lifetime) to oblique plane microscopy—a method that even without this added dimension was labeled by Nature Methods in 2021 as a ‘Method to Watch.’ Following instrument development and validation, we will explore cellular response to Burkholderia infections and antibiotic treatment in immortal cell lines followed by expansion to more realistic cellular environments (such as neuro-muscular junctions, NMJs) to test nerve agent simulants and their MCMs. As a microscopy platform, these methods hold the promise of being able to visualize a single infected cell (or a cellular compartment) and MCM treatment well before a larger and later organ/organism response.

47 OTHER INSTRUMENTATION↗
DOE OSTI2024

Quantification of heterogeneity in human CD8 + T cell responses to vaccine antigens: an HLA-guided perspective

Vaccines have historically played a pivotal role in controlling epidemics. Effective vaccines for viruses causing significant human disease, e.g., Ebola, Lassa fever, or Crimean Congo hemorrhagic fever virus, would be invaluable to public health strategies and counter-measure development missions. Here, we propose coverage metrics to quantify vaccine-induced CD8 + T cell-mediated immune protection, as well as metrics to characterize immuno-dominant epitopes, in light of human genetic heterogeneity and viral evolution. Proof-of-principle of our approach and methods are demonstrated for Ebola virus, SARS-CoV-2, and Burkholderia pseudomallei (vaccine) proteins.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2022

Effect of Endosymbiotic Bacteria on Fungal Resistance Toward Heavy Metals

Most studies on metal removal or tolerance by fungi or bacteria focus on single isolates, without taking into consideration that some fungi in nature may be colonized by endobacteria. To address this knowledge gap, we investigated the tolerance and removal of diverse metals with two fungal species: Linnemannia elongata containing Burkholderia-related endobacteria and Benniella erionia containing Mollicute-related endobacteria. Isogenic lines of both species were generated with antibiotic treatments to remove their respective endobacteria. Experiments involved comparing the isogenic lines and wild type fungi in relation to the minimum inhibitory concentration for the metals, the fungal ability to remove these different metals via atomic adsorption spectroscopy, and the interaction of the metals with specific functional groups of the fungi and fungi-bacteria to determine the role of the bacteria via attenuated total reflection fourier transformed infrared (ATR-FTIR). Finally, we determined the influence of different metal concentrations, associated with moderate and high fungal growth inhibition, on the presence of the endobacteria inside the fungal mycelium via quantitative real-time PCR. Results showed that the presence of the endosymbiont increased B. erionia resistance to Mn 2+ and increased the removal of Fe 2+ compared to isogenic lines. The absence of the endosymbiont in L. elongata increased the fungal resistance toward Fe 2+ and improved the removal of Fe 2+ . Furthermore, when the bacterial endosymbiont was present in L. elongata , a decrease in the fungal resistance to Ca 2+ , Fe 2+ , and Cr 6+ was noticeable. In the ATR-FTIR analysis, we determined that C-H and C = O were the major functional groups affected by the presence of Cu 2+ , Mn 2+ , and Fe 2+ for L. elongata and in the presence of Cu 2+ and Ca 2+ for B. eronia . It is noteworthy that the highest concentration of Pb 2+ led to the loss of endobacteria in both L. elongata and B. eronia , while the other metals generally increased the concentration of endosymbionts inside the fungal mycelium. From these results, we concluded that bacterial endosymbionts of fungi can play a fundamental role in fungal resistance to metals. This study provides the first step toward a greater understanding of symbiotic interactions between bacteria and fungi in relation to metal tolerance and remediation.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Exometabolite Dynamics over Stationary Phase Reveal Strain-Specific Responses

Nongrowth states are common for bacteria that live in environments that are densely populated and predominantly nutrient exhausted, and yet these states remain largely uncharacterized in cellular metabolism and metabolite output. Here, we investigated and compared stationary-phase exometabolites and RNA transcripts for each of three environmental bacterial strains.

59 BASIC BIOLOGICAL SCIENCES↗