Antimicrobial compounds produced by Lysinibacillus odysseyi epiphytic bacteria associated with red algae.

Seaweed epiphytic bacteria are highly host specific and their association is little known. The marine environment of Andaman Islands is rich in algal diversity and their association with microbial communities remains unexplored. We investigated the epiphytic bacterial communities from the intertidal red alga Gracilaria canaliculata. A total of four epiphytic bacterial isolates were cultured and screened for antimicrobial activity. Of the four isolates, one potential isolate, Gr102, exhibited strong antimicrobial activity in 0.50 μg/ml concentration against enteropathogenic Escherichia coli, Klebsiella pneumoniae, and Shigella flexneri. This potential isolate was characterized by genomic sequencing, fatty acid methyl ester analysis, and matrix-assisted laser desorption ionization-time of flight spectrometry, and the strain Gr102 was identified as Lysinibacillus odysseyi KC149512. Purified fractions obtained were analyzed by gas chromatography and mass spectrometry. Antimicrobial compounds such as furan, lupenol, diazene, and butenyl methyl ketone were identified. Based on the high level of activity, red algae epiphytic bacteria are potential sources of producing bioactive secondary metabolites.