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Abstract:
Chemoautotrophic bacteria belonging to the genus Sulfurimonas (class
Campylobacteria) were previously identified as key players in the
turnover of zero-valence sulfur, a central intermediate in the marine
sulfur cycle. S. denitrificans was further shown to be able to oxidize
cyclooctasulfur (S-8). However, at present the mechanism of activation
and metabolism of cyclooctasulfur is not known. Here, we assessed the
transcriptome and proteome of S. denitrificans grown with either
thiosulfate or S-8 as the electron donor. While the overall expression
profiles under the two growth conditions were rather similar, distinct
differences were observed that could be attributed to the utilization of
S-8. This included a higher abundance of expressed genes related to
surface attachment in the presence of S-8, and the differential
regulation of the sulfur-oxidation multienzyme complex (SOX), which in
S. denitrificans is encoded in two gene clusters: soxABXY(1)Z(1) and
soxCDY(2)Z(2). While the proteins of both clusters were present with
thiosulfate, only proteins of the soxCDY(2)Z(2) were detected at
significant levels with S-8. Based on these findings a model for the
oxidation of S-8 is proposed. Our results have implications for
interpreting metatranscriptomic and -proteomic data and for the observed
high level of diversification of soxY(2)Z(2) among sulfur-oxidizing
Campylobacteria.
