Gracilibacillus salinarum sp. nov. and Gracilibacillus caseinilyticus sp. nov., halotolerant bacteria isolated from a saltern environment

Two aerobic, Gram- stain-positive, spore-forming motile bacterial strains, designated SSPM10- 3T and SSWR10- 1T, were isolated from salterns in Jeollanam province of South Korea. Both strains were halotolerant and grew well in 5 % NaCl but not in 20 and 25% NaCl, respectively. Optimal growth was observed with 5 % NaCl, at 30 degrees C and at pH 7.0-8.0. On the basis of the results of phylogenetic analysis using 16S rRNA gene sequence, both the strains were placed within the genus Gracilibacillus with Gracilibacillus massiliensis (98.65 % similarity) as their nearest neighbour. Menaquinone- 7 (MK 7) (97 %) was the major isoprenoid quinone in both strains and major cellular fatty acids were anteiso-C15:0, iso-C15: 0 and anteiso-C17:0. Orthologous average nucleotide identity with usearch (OrthoANIu) and digital DNA-DNA hybridisation (dDDH) percentage comparison indicated that SSPM10- 3T and SSWR10- 1T exhibited highest similarity with G. massiliensis Awa-1T at 74.27 % and 21.0 and 74.23 % and 20.0 %, respectively. The DNA G+C contents of the strains were 39.1 % (SSPM10- 3T) and 38.5 % (SSWR10- 1T). Members of the genus Gracilibacillus, both strains were distinct from each other with respect to their ability to produce urease,beta-glucosidase, assimilation of inulin and methyl-alpha-o-glucopyranoside and degradation of casein. Compared with each other, ANI and d4 dDDH calculations were only 88.2 % and 36.3 %, well below the cut off values for species delineation for each index. On the basis of their phenotypic, physiological, biochemical and phylogenetic characteristics,SSPM10- 3T and SSWR10- 1T represent distinct novel species for which names Gracilibacillus salinarum SSPM10-3T and Gracilibacillus caseinilyticus SSWR10-1T are proposed. The type strains are SSPM10- 3T (=KACC 21933T =NBRC 115502T) and SSWR10- 1T (=KACC 21934T =NBRC 115503T).