Polyphasic characterization of and genomic insights into a haloalkali-tolerant Saccharibacillus alkalitolerans sp. nov., that produces three cellulase isozymes and several antimicrobial compounds.

A cellulase producing novel bacterial strain VR-M41 was isolated from an open-air vegetable and fruit market. Cells are found to be rod-shaped, endospore forming, positive for Gram's stain and negative for catalase, oxidase and urease. Strain VR-M41was halotolerant (upto 8.0% NaCl, w/v), motile and facultative anaerobe. It grew at wide range of pH (6.0-10.0) and temperatures (20-40 °C). Strain VR-M41 produced three isozymes of Carboxymethylcellulase. The 16S rRNA gene sequence of strain VR-M41was 97.3% similar to both Saccharibacillus kuerlensis DSM 22868 and Saccharibacillus sacchari DSM 19268, and less than 96.4% with the rest of the valid species of the genus Saccharibacillus. Whole-genome ANI, dDDH and genome phylogenetic tree analysis revealed that strain VR-M41 significantly differed from Saccharibacillus kuerlensis DSM 22868 and Saccharibacillus sacchari DSM 19268 (ANI 79.6-79.7% and dDDH 23.1%). The strain comprised of MK-7 and anteiso-C 15:0 (42.2%) as predominant isoprenoid quinone and fatty acid respectively. Major polar lipids were found to be diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine. The draft genome of strain VR-M41 consisted of 5,386,426 base pairs with 5103 annotated genes, out of which 2147 corresponded to hypothetical proteins and 2956 with functional assignments. Pan-genome analysis revealed the presence of 2998 core genes, 828 accessory genes, and 1131 unique genes of Saccharibacillus. Strain VR-M41 produced antimicrobials against Staphylococcus aureus, Streptococcus pneumoniae, Micrococcus luteus and Shigella flexneri. Significant phenotypic and genotypic differentiating characteristics from closely related species, indicated that strain VR-M41 is a novel species of the genus Saccharibacillus, for which the name Saccharibacillus alkalitolerans sp. nov., is proposed. The type strain is VR-M41 (= KCTC 43183=NBRC 114337).