Vibrio rubrogenes sp. nov., prodigiosin producing halophilic bacterium from seaweed Sargassum wightii of Mandapam coast, India

Seaweeds are known for their rich bioactive compounds with potential applications in biotechnological and industrial fields. However, seaweed associated bacteria are least explored for bioactive and other functional capabilities. A study aimed to bio-prospect seaweed associated bacteria for bioactive potential, a Gram-negative, rod shaped red pigmented strain SW71 was isolated from the seaweed thallus of Sargassum wightii, which exhibit unique biochemical and genomic characteristics. The strain was observed to be oxidase negative, and catalase positive. The isolate was positioned biochemically under Gazogenes clade of Vibrio, however the species delineation difficulties further went for molecular phylogenetic analysis. 16S rRNA analysis placed the isolate position to V. gazogenes by 97.94%. Whole genome sequence analysis showed that the proposed novel strain is closely identical to V. ruber and V. gazogenes with phylogenomic tree and the overall genome relatedness indices such as average nucleotide identity (ANIu) (89.95% and 87.92%), and digital DNA-DNA hybridization (dDDH) (38.5% and 34.4%) values. The value for dDDH against V. rhizosphaerae was 33%. However, the difficulty in species delineation further supported by ribosomal Multi-Locus Sequence Typing (MLST) analysis where the strain predicted as V. gazogenes with only 88% identity. The predominant fatty acids in the cellular fraction was C16:0 (23.47%), followed by C18:1 (17.23%), C22:1 (8.19%), C18:0 (7.64%), and C16:1 (4.91%). The major lipid classes detected were Phosphatidylethanolamine (34:2), Phosphatidylethanolamine (32:1), Galactosylceramide (d18:2/21:0), N-lauroylglycine, Phosphatidic acid (32:2), Diphosphatidyl glycerol (Cardiolipin) (68:4), and Phosphatidylserine (34:0). Gene mining and metabolomic profiling confirmed the red pigmentation by the presence of prodigiosin in the strain genome. Based on the phenotypic, genotypic and chemotypic analyses, the strain proposed as Vibrio rubrogenes sp. nov. strain smcift-1 T = MTCC 14081) here.