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Environ Microbiol. 2018 Mar 9. doi: 10.1111/1462-2920.14090. [Epub ahead of print]

Genomes of ubiquitous marine and hypersaline Hydrogenovibrio, Thiomicrorhabdus, and Thiomicrospira spp. encode a diversity of mechanisms to sustain chemolithoautotrophy in heterogeneous environments.

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Department of Integrative Biology, University of South Florida, 4202 East Fowler Avenue, Tampa, FL 33620, USA.
Biology Program, Stockton University, Galloway, New Jersey, USA.
Department of Energy Joint Genome Institute, Walnut Creek, CA, USA.
School of Biological & Marine Sciences, University of Plymouth, Drake Circus, Plymouth, UK; Sustainable Earth Institute, University of Plymouth, Drake Circus, Plymouth, UK.
Department of Biochemistry, University of Missouri, Columbia, Missouri, USA.
MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, USA, Department of Plant and Microbial Biology, University of California, Berkeley, USA, and MBIB Division, Lawrence Berkeley National Laboratory, Berkeley, USA.


Chemolithoautotrophic bacteria from the genera Hydrogenovibrio, Thiomicrorhabdus, and Thiomicrospira are common, sometimes dominant, isolates from sulfidic habitats including hydrothermal vents, soda and salt lakes, and marine sediments. Their genome sequences confirm their membership in a deeply branching clade of the Gammaproteobacteria. Several adaptations to heterogeneous habitats are apparent. Their genomes include large numbers of genes for sensing and responding to their environment (EAL- and GGDEF-domain proteins, and methyl-accepting chemotaxis proteins) despite their small sizes (2.1 - 3.1 Mbp). An array of sulfur-oxidizing complexes are encoded, likely to facilitate these organisms' use of multiple forms of reduced sulfur as electron donors. Hydrogenase genes are present in some taxa, including group 1d and 2b hydrogenases in Hydrogenovibrio marinus and H. thermophilus MA2-6, acquired via horizontal gene transfer. In addition to high-affinity cbb3 cytochrome c oxidase, some also encode cytochrome bd-type quinol oxidase or ba3 -type cytochrome c oxidase, which could facilitate growth under different oxygen tensions, or maintain redox balance. Carboxysome operons are present in most, with genes downstream encoding transporters from four evolutionarily distinct families, which may act with the carboxysomes to form CO2 concentrating mechanisms. These adaptations to habitat variability likely contribute to the cosmopolitan distribution of these organisms. This article is protected by copyright. All rights reserved.


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