AUTHOR=Pujalte María J. , Lucena Teresa , Rodrigo-Torres Lidia , Arahal David R. 

TITLE=Comparative Genomics of Thalassobius Including the Description of Thalassobius activus sp. nov., and Thalassobius autumnalis sp. nov.

JOURNAL=Frontiers in Microbiology

VOLUME=8

YEAR=2018

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2017.02645

DOI=10.3389/fmicb.2017.02645

ISSN=1664-302X

ABSTRACT=<p>A taxogenomic study was conducted to describe two new <italic>Thalassobius</italic> species and to analyze the internal consistency of the genus <italic>Thalassobius</italic> along with <italic>Shimia</italic> and <italic>Thalassococcus</italic>. Strains CECT 5113<sup>T</sup>, CECT 5114, CECT 5118<sup>T</sup>, and CECT 5120 were isolated from coastal Mediterranean seawater, Spain. Cells were Gram-negative, non- motile coccobacilli, aerobic chemoorganotrophs, with an optimum temperature of 26°C and salinity of 3.5–5%. Major cellular fatty acids of strains CECT 5113<sup>T</sup> and CECT 5114 were C<sub>18 : 1</sub> ω7c/ω6c and C<sub>10 : 0</sub> 3OH, G+C content was 54.4–54.5 mol% and were able to utilize propionate, L-threonine, L- arginine, and L-aspartate as carbon sources. They exhibited 98.3% 16S rRNA gene sequence similarity, 75.0–75.1 ANIb and 19.5–20.9 digital DDH to type strain of their closest species, <italic>Thalassobius maritimus</italic>. Based on these data, strains CECT 5113<sup>T</sup> and CECT 5114 are recognized as a new species, for which the name <italic>Thalassobius activus</italic> is proposed, with strain CECT 5113<sup>T</sup> (=LMG 29900<sup>T</sup>) as type strain. Strains CECT 5118<sup>T</sup> and CECT 5120 were found to constitute another new species, with major cellular fatty acids C<sub>18 : 1</sub> ω<italic>7c</italic>/ω<italic>6c</italic> and C<sub>18 : 1</sub> ω<italic>7c</italic> 11-methyl and a G+C content of 59.8 mol%; they were not able to utilize propionate, L-threonine, L- arginine or L-aspartate. Their closest species was <italic>Thalassobius mediterraneus</italic>, with values of 99.6% 16S rRNA gene sequence similarity, 79.1% ANIb and 23.2% digital DDH compared to the type strain, CECT 5383<sup>T</sup>. The name <italic>Thalassobius autumnalis</italic> is proposed for this second new species, with strain CECT 5118<sup>T</sup> (=LMG 29904<sup>T</sup>) as type strain. To better determine the phylogenetic relationship of the two new species, we submitted 12 genomes representing species of <italic>Thalassobius, Shimia</italic>, and <italic>Thalassoccocus</italic>, to a phylogenomic analysis based on 54 single protein-encoding genes (BCG54). The resulting phylogenomic tree did not agree with the current genera classification, as <italic>Thalassobius</italic> was divided in three clades, <italic>Thalassobius</italic> sensu stricto (<italic>T. mediterraneus, T. autumnalis</italic> sp. nov., and <italic>T. gelatinovorus</italic>), <italic>Thalassobius aestuarii</italic> plus the three <italic>Shimia</italic> spp (<italic>S. marina, S. haliotis</italic>, and <italic>Shimia</italic> sp. SK013) and finally, <italic>Thalasobius maritimus</italic> plus <italic>T. activus</italic> sp. nov. <italic>Thalassococcus halodurans</italic> remained apart from the two genera. Phenotypic inferences from explored genomes are presented.</p>