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Abstract:
Sulfur-oxidizing Sulfurimonas spp. are widespread in sediments,
hydrothermal vent fields, aquifers and subsurface environments such as
oil reservoirs where they play an important role in the sulfur cycle. We
determined the genome sequence of the oil field isolate Sulfurimonas sp.
strain CVO and compared its gene expression during nitrate-dependent
sulfide oxidation to the coastal sediment isolate Sulfurimonas
denitrificans. Formation of elemental sulfur (S-0) and high expression
of sulfide quinone oxidoreductase (SQR) genes indicates that sulfide
oxidation in both strains is mediated by SQR. Subsequent oxidation of
S-0 was achieved by the sulfur oxidation enzyme complex (SOX). In the
coastal S. denitrificans, the genes are arranged and expressed as two
clusters: soxXY(1)Z(1)AB and soxCDY(2)Z(2)H, and sulfate was the sole
metabolic end product. By contrast, the oil field strain CVO has only
the soxCDY(2)Z(2)H cluster and not soxXY(1)Z(1)AB. Despite the absence
of the soxXY(1)Z(1)AB cluster, strain CVO oxidized S-0 to thiosulfate
and sulfate, demonstrating that soxCDY(2)Z(2)H genes alone are
sufficient for S-0 oxidation in Sulfurimonas spp. and that thiosulfate
is an additional metabolic end product. Screening of publicly available
metagenomes revealed that Sulfurimonas spp. with only the soxCDY(2)Z(2)H
cluster are widespread suggesting this mechanism of thiosulfate
formation is environmentally significant.
