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Schlagwörter:
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Zusammenfassung:
Even in the current era of metagenomics, the interpretation of
nucleotide sequence data is primarily dependent on knowledge obtained
from a limited number of microbes isolated in pure culture. Thus, it is
of fundamental importance to expand the variety of strains available in
pure culture, to make reliable connections between physiological
characteristics and genomic information. In this study, two sulfur
oxidizers that potentially represent two novel species were isolated and
characterized. They were subjected to whole-genome sequencing together
with 7 neutrophilic and chemolithoautotrophic sulfur-oxidizing bacteria.
The genes for sulfur oxidation in the obtained genomes were identified
and compared with those of isolated sulfur oxidizers in the classes
Betaproteobacteria and Gammaproteobacteria. Although the combinations of
these genes in the respective genomes are diverse, typical combinations
corresponding to three types of core sulfur oxidation pathways were
identified. Each pathway involves one of three specific sets of
proteins, SoxCD, DsrABEFHCMKJOP, and HdrCBAHypHdrCB. All three core
pathways contain the SoxXYZAB proteins, and a cytoplasmic sulfite
oxidase encoded by soeABC is a conserved component in the core pathways
lacking SoxCD. Phylogenetically close organisms share same core sulfur
oxidation pathway, but a notable exception was observed in the family
'Sulfuricellaceae'. In this family, some strains have either core
pathway involving DsrABEFHCMKJOP or HdrCBAHypHdrCB, while others have
both pathways. A proteomics analysis showed that proteins constituting
the core pathways were produced at high levels. While hypothesized
function of HdrCBAHypHdrCB is similar to that of Dsr system, both sets
of proteins were detected with high relative abundances in the proteome
of a strain possessing genes for these proteins. In addition to the
genes for sulfur oxidation, those for arsenic metabolism were searched
for in the sequenced genomes. As a result, two strains belonging to the
families Thiobacillaceae and Sterohbacteriaceae were observed to harbor
genes encoding ArxAB, a type of arsenite oxidase that has been
identified in a limited number of bacteria. These findings were made
with the newly obtained genomes, including those from 6 genera from
which no genome sequence of an isolated organism was previously
available. These genomes will serve as valuable references to interpret
nucleotide sequences.
