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Analysis of a Ferric Uptake Regulator (Fur) Mutant ofDesulfovibrio vulgaris Hildenborough

Description: Previous experiments examining the transcriptional profileof the anaerobe Desulfovibrio vulgaris demonstrated up-regulation of theFur regulon in response to various environmental stressors. To test theinvolvement of Fur in the growth response and transcriptional regulationof D. vulgaris, a targeted mutagenesis procedure was used for deletingthe fur gene. Growth of the resulting ?fur mutant (JW707) was notaffected by iron availability, but the mutant did exhibit increasedsensitivity to nitrite and osmotic stresses compared to the wild type.Transcriptional profiling of JW707 indicated that iron-bound Fur acts asa traditional repressor for ferrous iron uptake genes (feoAB) and othergenes containing a predicted Fur binding site within their promoter.Despite the apparent lack of siderophore biosynthesis genes within the D.vulgaris genome, a large 12-gene operon encoding orthologs to TonB andTolQR also appeared to be repressed by iron-bound Fur. While other genespredicted to be involved in iron homeostasis were unaffected by thepresence or absence of Fur, alternative expression patterns that could beinterpreted as repression or activation by iron-free Fur were observed.Both the physiological and transcriptional data implicate a globalregulatory role for Fur in the sulfate-reducing bacterium D.vulgaris.
Date: September 21, 2007
Creator: Bender, Kelly S.; Yen, Huei-Che Bill; Hemme, Christopher L.; Yang, Zamin K.; He, Zhili; He, Qiang et al.
Partner: UNT Libraries Government Documents Department

Metagenomic Insights into Evolution of a Heavy Metal-Contaminated Groundwater Microbial Community

Description: Understanding adaptation of biological communities to environmental change is a central issue in ecology and evolution. Metagenomic analysis of a stressed groundwater microbial community reveals that prolonged exposure to high concentrations of heavy metals, nitric acid and organic solvents (~;;50 years) have resulted in a massive decrease in species and allelic diversity as well as a significant loss of metabolic diversity. Although the surviving microbial community possesses all metabolic pathways necessary for survival and growth in such an extreme environment, its structure is very simple, primarily composed of clonal denitrifying ?- and ?-proteobacterial populations. The resulting community is over-abundant in key genes conferring resistance to specific stresses including nitrate, heavy metals and acetone. Evolutionary analysis indicates that lateral gene transfer could be a key mechanism in rapidly responding and adapting to environmental contamination. The results presented in this study have important implications in understanding, assessing and predicting the impacts of human-induced activities on microbial communities ranging from human health to agriculture to environmental management, and their responses to environmental changes.
Date: February 15, 2010
Creator: Hemme, Christopher L.; Deng, Ye; Gentry, Terry J.; Fields, Matthew W.; Wu, Liyou; Barua, Soumitra et al.
Partner: UNT Libraries Government Documents Department

Distinctive Oxidative Stress Responses to Hydrogen Peroxide in Sulfate Reducing Bacteria Desulfovibrio vulgaris Hildenborough

Description: Response of Desulfovibrio vulgaris Hildenborough to hydrogen peroxide (H2O2, 1 mM) was investigated with transcriptomic, proteomic and genetic approaches. Microarray data demonstrated that gene expression was extensively affected by H2O2 with the response peaking at 120 min after H2O2 treatment. Genes affected include those involved with energy production, sulfate reduction, ribosomal structure and translation, H2O2 scavenging, posttranslational modification and DNA repair as evidenced by gene coexpression networks generated via a random matrix-theory based approach. Data from this study support the hypothesis that both PerR and Fur play important roles in H2O2-induced oxidative stress response. First, both PerR and Fur regulon genes were significantly up-regulated. Second, predicted PerR regulon genes ahpC and rbr2 were derepressedin Delta PerR and Delta Fur mutants and induction of neither gene was observed in both Delta PerR and Delta Fur when challenged with peroxide, suggesting possible overlap of these regulons. Third, both Delta PerR and Delta Fur appeared to be more tolerant of H2O2 as measured by optical density. Forth, proteomics data suggested de-repression of Fur during the oxidative stress response. In terms of the intracellular enzymatic H2O2 scavenging, gene expression data suggested that Rdl and Rbr2 may play major roles in the detoxification of H2O2. In addition, induction of thioredoxin reductase and thioredoxin appeared to be independent of PerR and Fur. Considering all data together, D. vulgaris employed a distinctive stress resistance mechanism to defend against increased cellular H2O2, and the temporal gene expression changes were consistent with the slowdown of cell growth at the onset of oxidative stress.
Date: January 1, 2009
Creator: Zhou, Aifen; He, Zhili; Redding, A.M.; Mukhopadhyay, Aindrila; Hemme, Christopher L.; Joachimiak, Marcin P. et al.
Partner: UNT Libraries Government Documents Department