Two strains, 08MAS2251T and LZ2016-166, were isolated from diverse samples in China collected from the surface of crucian carp and the faeces of a diarrhoea patient, respectively. Both strains were pink-orange coloured, Gram-negative, oxidase- and catalase-positive, facultative anaerobic and motile bacteria, produced H2S and reduced nitrates to nitrites. Growth occurred in the presence of 0-9 % (w/v) NaCl and at 10-42 °C. The optimum conditions were with 1 % (w/v) NaCl and at 35 °C. The phylogenetic tree of 16S rRNA gene demonstrated that strains 08MAS2251T and LZ2016-166 clustered in a distinctive clade next to the species Shewanella chilikensis JC5T within the genus Shewanella. Meanwhile, gyrB gene sequence analysis indicated that the two strains formed an independent branch that was clearly separate from all the other Shewanella species with sequence similarities from 68.49 to 95.74 %. The DNA G+C content of strain 08MAS2251T was 52.68 mol%. Genomic relatedness of in silico DNA-DNA hybridization between strain 08MAS2251T and phylogenetic neighbours ranged from 50.5-51.8 %, below the cutoff of 70 %. In addition, corresponding average nucleotide identity values were between 93.01 to 93.49%, which were lower than 95 % threshold. The major fatty acids of strain 08MAS2251T were C17 : 1ω8c (27.2 %), iso-C15 : 0 (22.5 %), summed feature 3 (C16 : 1ω6c and/or C16 : 1ω7c; 8.7 %), C16 : 0 (6.2 %), iso-C13 : 0 (5.6 %) and C17 : 0 (4.5 %). Based on phenotypic and genetic analysis, strains 08MAS2251T and LZ2016-166 are identified as a novel species of the genus Shewanella, for which the name Shewanellacarassii sp. nov. is proposed. The type strain is 08MAS2251T (=DSM 104682T=CGMCC 1.16033T).
Keywords: 16S rRNA gene; Shewanella; average nucleotide identity; gyrB; in silico DNA-DNA hybridization.