Affiliation:
1. School of Biology, Georgia Institute of Technology, Atlanta, Georgia 30332
Abstract
ABSTRACT
Shewanella oneidensis
MR-1, a facultatively anaerobic gammaproteobacterium, respires a variety of anaerobic terminal electron acceptors, including the inorganic sulfur compounds sulfite (SO
3
2−
), thiosulfate (S
2
O
3
2−
), tetrathionate (S
4
O
6
2−
), and elemental sulfur (S
0
). The molecular mechanism of anaerobic respiration of inorganic sulfur compounds by
S. oneidensis
, however, is poorly understood. In the present study, we identified a three-gene cluster in the
S. oneidensis
genome whose translated products displayed 59 to 73% amino acid similarity to the products of
phsABC
, a gene cluster required for S
0
and S
2
O
3
2−
respiration by
Salmonella enterica
serovar Typhimurium LT2. Homologs of
phsA
(annotated as
psrA
) were identified in the genomes of
Shewanella
strains that reduce S
0
and S
2
O
3
2−
yet were missing from the genomes of
Shewanella
strains unable to reduce these electron acceptors. A new suicide vector was constructed and used to generate a markerless, in-frame deletion of
psrA
, the gene encoding the putative thiosulfate reductase. The
psrA
deletion mutant (PSRA1) retained expression of downstream genes
psrB
and
psrC
but was unable to respire S
0
or S
2
O
3
2−
as the terminal electron acceptor. Based on these results, we postulate that PsrA functions as the main subunit of the
S. oneidensis
S
2
O
3
2−
terminal reductase whose end products (sulfide [HS
−
] or SO
3
2−
) participate in an intraspecies sulfur cycle that drives S
0
respiration.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
108 articles.
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