Abstract
Carbon monoxide (CO) is a potential energy and carbon source for thermophilic bacteria in geothermal environments. Geothermal sites ranging in temperature from 45 to 65°C were investigated for the presence and activity of anaerobic CO-oxidizing bacteria. Anaerobic CO oxidation potentials were measured at up to 48.9 μmoles CO g−1 (wet weight) day−1 within five selected sites. Active anaerobic carboxydotrophic bacteria were identified using 13CO DNA stable isotope probing (SIP) combined with pyrosequencing of 16S rRNA genes amplified from labeled DNA. Bacterial communities identified in heavy DNA fractions were predominated by Firmicutes, which comprised up to 95% of all sequences in 13CO incubations. The predominant bacteria that assimilated 13C derived from CO were closely related (>98% 16S rRNA gene sequence identity) to genera of known carboxydotrophs including Thermincola, Desulfotomaculum, Thermolithobacter, and Carboxydocella, although a few species with lower similarity to known bacteria were also found that may represent previously unconfirmed CO-oxidizers. While the distribution was variable, many of the same OTUs were identified across sample sites from different temperature regimes. These results show that bacteria capable of using CO as a carbon source are common in geothermal springs, and that thermophilic carboxydotrophs are probably already quite well known from cultivation studies.
Highlights
Carbon monoxide (CO) is an odorless gas toxic to many animals due to its competitive binding to hemoglobin (Haab, 1990)
While the distribution was variable, many of the same operational taxonomic units (OTUs) were identified across sample sites from different temperature regimes. These results show that bacteria capable of using CO as a carbon source are common in geothermal springs, and that thermophilic carboxydotrophs are probably already quite well known from cultivation studies
Bacteria potentially involved in the anaerobic oxidation of carbon monoxide were identified from hot spring environments using DNA-stable isotope probing (SIP)
Summary
Carbon monoxide (CO) is an odorless gas toxic to many animals due to its competitive binding to hemoglobin (Haab, 1990). There are numerous natural biogenic and abiogenic sources of CO. Thermal decomposition and photochemical degradation of organic compounds are important sources of abiotic CO (Sipma et al, 2006). CO is a component of volcanic emissions, which may contain as much as 1–2% of CO per volume of total gas (Giggenbach, 1980; Svetlichny et al, 1991a; Sokolova et al, 2009 and references therein). Biogenic CO may be produced in microbial ecosystems, and net CO production has been reported for marine algae (Conrad, 1988) and hypersaline cyanobacterial mats (Hoehler et al, 2001) during photosynthesis. Some microbes growing in high temperature environments are likely capable of growth at low concentrations of CO (Sokolova et al, 2009).
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