Distribution and Diversity of Aerobic Carbon Monoxide-Oxidizing Bacteria in Geothermal Springs of China, the Philippines, and the United States

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Accumulating genomic evidence suggests that a variety of thermophilic bacteria contain cox operons and may be capable of aerobic carbon monoxide (CO) oxidation. However, little is known about the distribution and diversity of the cox-encoding (COXE) bacteria in natural geothermal environments. In this study, we examined coxL gene (encoding the large subunit of carbon monoxide dehydrogenase: CoxL) sequences retrieved from the sediments of 25 geothermal sites located in the Qinghai-Tibetan Plateau (QTP) and Yunnan Province (YP) of China, the Bacon-Manito Geothermal Production Field (BGPF) of the Philippines, and the Great Basin of the United States (USGB). Temperature and pH ranges of the studied hot springs were 22.1 to 90.8°C and 2.7 to 9.4, respectively. Phylogenetic analyses showed that most CoxL sequences were closely related to the classes Actinobacteria, Deinococci, Ktedonobacteria, Thermomicrobia, and Clostridia, and hot springs from different regions hosted different COXE communities. In addition, these hot springs harbored some COXE bacteria that were phylogenetically distinct from those inhabiting nongeothermal ecosystems. This study revealed no significant correlation between temperature or pH and the composition or diversity of COXE communities at the global scale. However, within a given region, temperature was correlated with the COXE bacterial community composition.