AUTHOR=Wang Pei , Li Liang Zhi , Qin Ya Ling , Liang Zong Lin , Li Xiu Tong , Yin Hua Qun , Liu Li Jun , Liu Shuang-Jiang , Jiang Cheng-Ying 

TITLE=Comparative Genomic Analysis Reveals the Metabolism and Evolution of the Thermophilic Archaeal Genus Metallosphaera

JOURNAL=Frontiers in Microbiology

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2020.01192

DOI=10.3389/fmicb.2020.01192

ISSN=1664-302X

ABSTRACT=<p>Members of the genus <italic>Metallosphaera</italic> are widely found in sulfur-rich and metal-laden environments, but their physiological and ecological roles remain poorly understood. Here, we sequenced <italic>Metallosphaera tengchongensis</italic> Ric-A, a strain isolated from the Tengchong hot spring in Yunnan Province, China, and performed a comparative genome analysis with other <italic>Metallosphaera</italic> genomes. The genome of <italic>M. tengchongensis</italic> had an average nucleotide identity (ANI) of approximately 70% to that of <italic>Metallosphaera cuprina</italic>. Genes <italic>sqr</italic>, <italic>tth</italic>, <italic>sir</italic>, <italic>tqo</italic>, <italic>hdr</italic>, <italic>tst</italic>, <italic>soe</italic>, and <italic>sdo</italic> associated with sulfur oxidation, and gene clusters <italic>fox</italic> and <italic>cbs</italic> involved in iron oxidation existed in all <italic>Metallosphaera</italic> genomes. However, the adenosine-5′-phosphosulfate (APS) pathway was only detected in <italic>Metallosphaera sedula</italic> and <italic>Metallosphaera yellowstonensis</italic>, and several subunits of <italic>fox</italic> cluster were lost in <italic>M. cuprina</italic>. The complete 3-hydroxypropionate/4-hydroxybutyrate cycle and dicarboxylate/4-hydroxybutyrate cycle involved in carbon fixation were found in all <italic>Metallosphaera</italic> genomes. A large number of gene family gain events occurred in <italic>M. yellowstonensis</italic> and <italic>M. sedula</italic>, whereas gene family loss events occurred frequently in <italic>M. cuprina.</italic> Pervasive strong purifying selection was found acting on the gene families of <italic>Metallosphaera</italic>, of which transcription-related genes underwent the strongest purifying selection. In contrast, genes related to prophages, transposons, and defense mechanisms were under weaker purifying pressure. Taken together, this study expands knowledge of the genomic traits of <italic>Metallosphaera</italic> species and sheds light on their evolution.</p>