Francisella salimarina sp. nov., isolated from coastal seawater

Four strains (SYSU SYW-1(T), SYW-2, SYW-3 and XLW-1) were isolated from seawater near the shore in Guangdong Province, China. Cells were Gram-stain-negative, aerobic, non-motile and non-spore-forming. Growth was observed at a temperature range of 16-40 degrees C (optimum, 32 degrees C), a pH range of 4-8 (optimum, pH 7) and in the presence of up to 10% (w/v) NaCl. The major polar lipids were diphosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine and an unidentified phospholipid. The respiratory quinone was ubiquinone 8 (UQ-8), and the predominant fatty acids were C-19:0 3-OH, C-1(0:)0, C-14:0 and C-18:1 omega 9c. Comparison of 16S rRNA gene and genome sequences confirmed that these strains represented a novel member of the genus Francisella, with less than 98.8% 16S rRNA gene sequence similarity and less than 95% genomic average nucleotide identity to recognized Francisella species. The phylogenetic tree based on 16S rRNA gene sequences and the protein-concatamer tree based on a concatenation of 28 protein marker sequences both indicated that the strains clustered with 'Francisella saline' TX07-7308 and 'Francisella marina' E95-16, but formed a distinct lineage group among the other members of the genus Francisella. The DNA G+C contents of the four strains were determined to be 32.9, 32.7, 32.9 and 32.9%, respectively (genome). On the basis of phenotypic and genotypic features, the strains are considered to represent a novel species of the genus Francisella, for which the name Francisella salimarina sp. nov. is proposed. The type strain is SYSU SYW-1(T) (=CGMCC 1.17031(T)=NBRC 113781(T)).