Strain CECT 7735T, a marine Gram-reaction negative, aerobic, non-motile bacterium, was isolated from coastal seawater in Valencia, Spain. Strain CECT 7735T is chemoorganotrophic, mesophilic, slightly halophilic, grows at 15-28 °C but not at 4 or 37 °C, requires seawater for growth and grows up to 6 % salinity. The major cellular fatty acid is summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c). The G+C content of the genome is 55.7 mol%. Comparative analysis of the 16S rRNA gene sequence shows the strain is affiliated to the family Rhodobacteraceae, in the class Alphaproteobacteria, with highest similarities to Phaeobacter species (97.0-97.5 %), Shimia species (96.5-97.3 %) and Pseudopelagicola gijangensis (96.5 %). Further phylogenomic analysis through the up-to-date-bacterial core gene (UBCG) set showed P. gijangensis to be its closest relative. Average nucleotide identity and in silico DNA-DNA hybridization values are lower than 85 and 21 %, respectively, with its phylogenetic relatives, suggesting that strain CECT 7735T represents a new species. The average amino acid identity value was over 70 % with the genome of the type strain of P. gijangensis and with all those of Shimia species. These values, together with UBCG set trees, suggest that the new species and P. gijangensisbelong to the same genus and that Pseudopelagicola should be reclassified as a Shimia species. We conclude that strain CECT 7735T represents a new species in the genus Shimia, for which we propose the name Shimiathalassica sp. nov. In addition, Pseudopelagicola gijangensis is reclassified as Shimiagijangensis comb. nov. From the same phylogenomic study, it can be concluded that Thalassobius activus should be reclassified in the genus Cognatishimia as Cognatishimiaactiva comb. nov.
Keywords: AAI; ANI; Cognatishimia; Pseudopelagicola; Rhodobacteraceae; Shimia; marine bacteria.