Affiliation:
1. Department of Microbiology, Bose Institute, Calcutta, India
2. Gas Hydrate Research Group, Geological Oceanography, CSIR—National Institute of Oceanography, Dona Paula, Goa, India
Abstract
During chemolithoautotrophic thiosulfate oxidation, the phylogenetically diverged proteobacteria
Paracoccus pantotrophus
,
Tetrathiobacter kashmirensis
, and
Thiomicrospira crunogena
rendered steady enrichment of
34
S in the end product sulfate, with overall fractionation ranging between −4.6‰ and +5.8‰. The fractionation kinetics of
T. crunogena
was essentially similar to that of
P. pantotrophus
, albeit the former had a slightly higher magnitude and rate of
34
S enrichment. In the case of
T. kashmirensis
, the only significant departure of its fractionation curve from that of
P. pantotrophus
was observed during the first 36 h of thiosulfate-dependent growth, in the course of which tetrathionate intermediate formation is completed and sulfate production starts. The almost-identical
34
S enrichment rates observed during the peak sulfate-producing stage of all three processes indicated the potential involvement of identical S-S bond-breaking enzymes. Concurrent proteomic analyses detected the hydrolase SoxB (which is known to cleave terminal sulfone groups from SoxYZ-bound cysteine
S
-thiosulfonates, as well as cysteine
S
-sulfonates, in
P. pantotrophus
) in the actively sulfate-producing cells of all three species. The inducible expression of
soxB
during tetrathionate oxidation, as well as the second leg of thiosulfate oxidation, by
T. kashmirensis
is significant because the current Sox pathway does not accommodate tetrathionate as one of its substrates. Notably, however, no other Sox protein except SoxB could be detected upon matrix-assisted laser desorption ionization mass spectrometry analysis of all such
T. kashmirensis
proteins as appeared to be thiosulfate inducible in 2-dimensional gel electrophoresis. Instead, several other redox proteins were found to be at least 2-fold overexpressed during thiosulfate- or tetrathionate-dependent growth, thereby indicating that there is more to tetrathionate oxidation than SoxB alone.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
26 articles.
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