Matching Items (3)
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- All Subjects: Bacteria
- Creators: Wang, Xuan
Description
Peatlands represent 3% of the earth’s surface but have been estimated to contain up to 30% of all terrestrial soil organic carbon and release an estimated 40% of global atmospheric CH4 emissions. Contributors to the production of CH4 are methanogenic Archaea through a coupled metabolic dependency of end products released by heterotrophic bacteria within the soil in the absence of O2. To better understand how neighboring bacterial communities can influence methanogenesis, the isolation and physiological characterization of two novel isolates, one Methanoarchaeal isolate and one Acidobacterium isolate identified as QU12MR and R28S, respectively, were targeted in this present study. Co-culture growth in varying temperatures of the QU12MR isolate paired with an isolated Clostridium species labeled R32Q and the R28S isolate were also investigated for possible influences in CH4 production. Phylogenetic analysis of strain QU12MR was observed as a member of genus Methanobacterium sharing 98% identity similar to M. arcticum strain M2 and 99% identity similar to M. uliginosum strain P2St. Phylogenetic analysis of strain R28S was associated with genus Acidicapsa from the phylum Acidobacteria, sharing 97% identity to A. acidisoli strain SK-11 and 96% identity similarity to Occallatibacter savannae strain A2-1c. Bacterial co-culture growth and archaeal CH4 production was present in the five temperature ranges tested. However, bacterial growth and archaeal CH4 production was less than what was observed in pure culture analysis after 21 days of incubation.
ContributorsRamirez, Zeni Elizia (Author) / Cadillo-Quiroz, Hinsby (Thesis advisor) / Roberson, Robert (Thesis advisor) / Wang, Xuan (Committee member) / Arizona State University (Publisher)
Created2018
Description
Fermentative bioproduction is an efficient production avenue for many small organic acids with less greenhouse gas emissions than petrochemical conversion. Export of these organic acids from the cell is proposed to be mediated by networks of transmembrane transport proteins. However characterization of full transporter networks or the substrate promiscuity of individual transporters is often incomplete. Here, we used a cheminformatic approach to predict previously unknown native activity of E. coli transporters based on substrate promiscuity. Experimental validation in characterized several major putative malate exporters, whereas others were characterized as weak putative lactate exporters. The lactate export network remains incompletely characterized and might be mediated by a large, evolved network of promiscuous transporters.
ContributorsSchneider, Aidan (Author) / Wang, Xuan (Thesis director) / Varman, Arul (Committee member) / Nielsen, David (Committee member) / Department of Finance (Contributor) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2018-12
Description
Abiotic stresses, such as heat, can drive protein misfolding and aggregation, leading to inhibition of cellular function and ultimately cell death. Unexpectedly, a thermotolerant Escherichia coli was identified from a pool of antibiotic resistant RNA polymerase β subunit (rpoB) mutants. This stress tolerant phenotype was characterized through exposure to high temperature and ethanol. After 30-minute exposure of cells to 55°C or 25% ethanol, the mutant displayed 100 times greater viability than the wild-type, indicating that the rpoB mutation may have broadly affected the cellular environment to reduce protein misfolding and/or prevent protein aggregation. To further test this hypothesis, we examined thermotolerance of cells lacking heat shock chaperone DnaJ (Hsp40), which is a cochaperone of one of the most abundant and conserved chaperones, DnaK (Hsp70). The deletion of dnaJ led to severe growth defects in the wild-type, namely a slower growth rate and extreme filamentation at 42°C. The severity of the growth defects increased after additionally deleting DnaJ analog, CbpA. However, these defects were significantly ameliorated by the rpoB mutation. Finally, the rpoB mutant was found to be minimally affected by the simultaneous depletion of DnaK and DnaJ compared to the wild-type, which failed to form single colonies at 37°C and 42°C. Based on these observations, it is proposed that the rpoB mutant’s robust thermotolerant phenotype results from a cellular environment protective against protein aggregation or improper folding. The folding environment of the rpoB mutants should be further examined to elucidate the mechanism by which both antibiotic resistance and thermotolerance can be conferred.
ContributorsYeh, Melody (Author) / Misra, Rajeev (Thesis director) / Wang, Xuan (Committee member) / Kelly, Keilen (Committee member) / School of Life Sciences (Contributor) / School of International Letters and Cultures (Contributor) / School of Human Evolution & Social Change (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05