AUTHOR=Emerson David , Field Erin , Chertkov Olga , Davenport Karen , Goodwin Lynne , Munk Christine , Nolan Matt , Woyke Tanja 

TITLE=Comparative genomics of freshwater Fe-oxidizing bacteria: implications for physiology, ecology, and systematics

JOURNAL=Frontiers in Microbiology

VOLUME=4

YEAR=2013

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2013.00254

DOI=10.3389/fmicb.2013.00254

ISSN=1664-302X

ABSTRACT=<p>The two microaerophilic, Fe-oxidizing bacteria (FeOB) <italic>Sideroxydans</italic> ES-1 and <italic>Gallionella</italic> ES-2 have single circular chromosomes of 3.00 and 3.16 Mb that encode 3049 and 3006 genes, respectively. Multi-locus sequence analysis (MLSA) confirmed the relationship of these two organisms to one another, and indicated they may form a novel order, the Gallionellalaes, within the Betaproteobacteria. Both are adapted for chemolithoautotropy, including pathways for CO<sub>2</sub>-fixation, and electron transport pathways adapted for growth at low O<sub>2</sub>-levels, an important adaptation for growing on Fe(II). Both genomes contain Mto-genes implicated in iron-oxidation, as well as other genes that could be involved in Fe-oxidation. Nearly 10% of their genomes are devoted to environmental sensing, signal transduction, and chemotaxis, consistent with their requirement for growing in narrow redox gradients of Fe(II) and O<sub>2</sub>. There are important differences as well. <italic>Sideroxydans</italic> ES-1 is more metabolically flexible, and can utilize reduced S-compounds, including thiosulfate, for lithotrophic growth. It has a suite of genes for nitrogen fixation. <italic>Gallionella</italic> ES-2 contains additional gene clusters for exopolysaccharide production, and has more capacity to resist heavy metals. Both strains contain genes for hemerythrins and globins, but ES-1 has an especially high numbers of these genes that may be involved in oxygen homeostasis, or storage. The two strains share homology with the marine FeOB <italic>Mariprofundus ferrooxydans</italic> PV-1 in CO<sub>2</sub> fixation genes, and respiratory genes. In addition, ES-1 shares a suite of 20 potentially redox active genes with PV-1, as well as a large prophage. Combined these genetic, morphological, and physiological differences indicate that these are two novel species, <italic>Sideroxydans lithotrophicus</italic> ES-1<sup>T</sup> (ATCC 700298<sup>T</sup>; JCM 14762; DSMZ 22444; NCMA B100), and <italic>Gallionella capsiferriformans</italic> ES-2<sup>T</sup> (ATCC 700299<sup>T</sup>; JCM 14763; DSMZ 22445; NCMA B101).</p>