title: Physiological response of Desulfurispirillum indicum S5 to arsenate and nitrate as terminal electron acceptors.
abstract: The ability of anaerobic prokaryotes to employ different terminal electron acceptors for respiration enables these organisms to flourish in subsurface ecosystems. Desulfurispirillum indicum strain S5 is an obligate anaerobic bacterium that is able to grow by respiring a range of different electron acceptors, including arsenate and nitrate. Here, we examined the growth, electron acceptor utilization, and gene expression of D. indicum growing under arsenate and nitrate-reducing conditions. Consistent with thermodynamic predictions, the experimental results showed that the reduction of nitrate to ammonium yielded higher cell densities than the reduction of arsenate to arsenite. However, D. indicum grew considerably faster by respiration on arsenate compared with nitrate, with doubling times of 4.3 ± 0.2 h and 19.2 ± 2.0 h, respectively. Desulfurispirillum indicum growing on both electron acceptors exhibited the preferential utilization of arsenate before nitrate. The expression of the arsenate reductase gene arrA was up-regulated approximately 100-fold during arsenate reduction, as determined by qRT-PCR. Conversely, the nitrate reductase genes narG and napA were not differentially regulated under the conditions tested. The results of this study suggest that physiology, rather than thermodynamics, controls the growth rates and hierarchy of electron acceptor utilization in D. indicum.
authors.affiliation: Department of Biochemistry and Microbiology, School of Environmental and Biological Sciences, Rutgers University, New Brunswick, NJ 08901, USA.
authors.forename: Ines
authors.initials: I
authors.lastname: Rauschenbach
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Bini
authors.forename: Max M
authors.initials: MM
authors.lastname: Häggblom
authors.forename: Nathan
authors.initials: N
authors.lastname: Yee
mesh_terms: D053502:Arsenate Reductases / Q000235:genetics / Q000378:metabolism; D001149:Arsenates / Q000378:metabolism*; D018053:Arsenites; D001419:Bacteria / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D050901:Nitrate Reductase / Q000235:genetics / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism*; D016877:Oxidants / Q000378:metabolism
chemical_list: D001149:Arsenates; D018053:Arsenites; D009566:Nitrates; D016877:Oxidants; D053502:Arsenate Reductases; D050901:Nitrate Reductase; C015001:arsenite; C025657:arsenic acid