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Inhibitory effects of uranium(VI) on...

Wen, Yi.

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Inhibitory effects of uranium(VI) on bacterial metabolism and transcriptional response of Shewanella oneidensis MR-1 to uranium stress.

Record Type:	Language materials, printed : Monograph/item
Title/Author:	Inhibitory effects of uranium(VI) on bacterial metabolism and transcriptional response of Shewanella oneidensis MR-1 to uranium stress./
Author:	Wen, Yi.
Description:	122 p.
Notes:	Adviser: James Leckie.
Contained By:	Dissertation Abstracts International69-02B.
Subject:	Biogeochemistry. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3302883
ISBN:	9780549489320

Inhibitory effects of uranium(VI) on bacterial metabolism and transcriptional response of Shewanella oneidensis MR-1 to uranium stress.
Wen, Yi.

Inhibitory effects of uranium(VI) on bacterial metabolism and transcriptional response of Shewanella oneidensis MR-1 to uranium stress. - 122 p.

Adviser: James Leckie.

Thesis (Ph.D.)--Stanford University, 2008.

Uranium is a contaminant of great environmental concern. The US Department of Energy (DOE) identified 120 sites in 36 states and territories; most of them are contaminated with uranium. Bioremediation has been considered as a potential strategy to remove uranium form the contaminated sites. However, uranium can have deleterious effects on microorganisms, such as inhibiting microbial metabolism, and reducing microbial growth. How uranium impacts microbial activities must be understood to avoid the potentially deleterious effect of uranium in bioremediation efforts. This dissertation researched the inhibitory effects of uranium(VI) on bacterial metabolic activities and aims to understand the mechanism of uranium stress on bacterial metabolism.

ISBN: 9780549489320Subjects--Topical Terms:

545717
Biogeochemistry.

Inhibitory effects of uranium(VI) on bacterial metabolism and transcriptional response of Shewanella oneidensis MR-1 to uranium stress.
LDR:05698nam 2200325 a 45 001 962845
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020 $a 9780549489320
035 $a (UMI)AAI3302883
035 $a AAI3302883
040 $a UMI $c UMI
100 1 $a Wen, Yi. $3 1285908
245 1 0 $a Inhibitory effects of uranium(VI) on bacterial metabolism and transcriptional response of Shewanella oneidensis MR-1 to uranium stress.
300 $a 122 p.
500 $a Adviser: James Leckie.
500 $a Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 0886.
502 $a Thesis (Ph.D.)--Stanford University, 2008.
520 $a Uranium is a contaminant of great environmental concern. The US Department of Energy (DOE) identified 120 sites in 36 states and territories; most of them are contaminated with uranium. Bioremediation has been considered as a potential strategy to remove uranium form the contaminated sites. However, uranium can have deleterious effects on microorganisms, such as inhibiting microbial metabolism, and reducing microbial growth. How uranium impacts microbial activities must be understood to avoid the potentially deleterious effect of uranium in bioremediation efforts. This dissertation researched the inhibitory effects of uranium(VI) on bacterial metabolic activities and aims to understand the mechanism of uranium stress on bacterial metabolism.
520 $a The metabolism of model organisms including Shewanella oneidensis strain MR-1, Pseudomonas putida strain KT2440 and Bacillus subtilis strain 168 was monitored under U(VI) stress using batch experiments. The presence of U(VI) inhibited the substrate degradation by bacteria. Uranium distribution in the biosystems studied shows that bacterial cells have high affinity for binding uranyl. Transmission electron microscopy (TEM) images indicate that the uranium bound to Shewanella oneidensis strain MR-1 cells are essentially associated with the phospholipid bi-layers of the outer and cytoplasmic membranes. Energy dispersed X-ray (EDAX) analysis gives a U:P molecule ratio of about 1 where uranium is heavily bound on the cell surface.
520 $a Gene expression profiles of Shewanella oneidensis strain MR-1 under uranium(VI) stress were examined over time using whole-genome DNA microarrays. Approximately 18% of the total 4648 predicted S. oneidensis genes represented on the microarray were significantly differentially expressed during exposure to U(VI) The changes in gene expression under uranium stress were sustained over the 80-min study period. The most significantly upregulated genes include genes encoding transport and binding proteins, as well as the genes involved in energy metabolism, cellular processes and protein fate. A substantial number of genes encoding membrane proteins and genes responding to membrane stress were highly upregulated over time, suggesting uranium posed a threat to cell membranes and may disrupt the functions of cell membrane components and cause misfolding of proteins. Many genes encoding metal efflux proteins were upregulated indicating possible detoxification mechanisms.
520 $a The upregulation of many genes encoding c-type cytochromes, which are essential for the U(VI) reduction, was not observed from the microarray data. Aerobic characterization of the CcmC mutant deficient in U(VI) reduction strongly suggests that U(VI) reduction via cytochromes as a detoxification mechanism under uranium stress may not be activated under aerobic conditions.
520 $a The in-frame deletion mutant lacking gene so0150 (putative lipoprotein), so0820 (HlyD family secretion protein), so1809 (phage shock protein C) or so4476 (putative spheroplast protein y precursor) were generated and characterized under uranium stress. The results confirm that these genes highly upregulated under uranium stress did play a role in mitigating the inhibitory effects of uranium on bacterial growth. The lack of genes that assist uranium resistance or inhibiting the processes involved in uranium resistance causes the cells more to be vulnerable to uranium stress. However, it did not change the distribution of uranium in the biotic systems. The gene expression profiles of MR-1 under uranium stress were compared with those of MR-1 under other metal ions stress conditions including As(V), Cd(II), Co(II), Cu(II), Ni(II), Pb(II), and Zn(II). Thirty-two genes up-regulated only under uranium stress were identified, among which thirteen of them encode transport and binding proteins. The functional categories of those genes suggest the activities of both protein efflux systems and multidrug pumps in MR-1 under uranium stress, indicating the efflux pumps may be activated as uranium detoxification responses by MR-1. These genes were only upregulated under uranium stress and can be used as potential marker genes for uranium stress.
520 $a In conclusion, this research has shown that U(VI) inhibits bacterial metabolic activities. The inhibitory effects are caused by the uranium bound to the bacterial cell membranes. The insights provided in this study are important for understanding the mechanisms of uranium inhibition on bacteria and the response of bacteria to uranium stress. Further investigation of the genes of interest pointed out in the microarray study will provide mechanistic insights on the uranium detoxification mechanisms in bacteria.
590 $a School code: 0212.
650 4 $a Biogeochemistry. $3 545717
690 $a 0425
710 2 $a Stanford University. $3 754827
773 0 $t Dissertation Abstracts International $g 69-02B.
790 $a 0212
790 1 0 $a Leckie, James, $e advisor
791 $a Ph.D.
792 $a 2008
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3302883