Screening for Bacteriocin-Like Antimicrobial Activity Against Shrimp Pathogenic Vibrios and Molecular Identification of Marine Bacteria from Otter Clam Lutraria philippinarum

Abstract

This study aimed to isolate marine bacteria from otter clam Lutraria philippinarum, screen for bacteriocin-like antimicrobial activity against shrimp pathogenic vibrios and identify these bacteria by molecular methods. Among a total of 128 bacterial isolates, 19 (15%) were found to produce bacteriocins against at least one of three shrimp pathogenic Vibrio strains. The highest bacteriocin production activity was shown by six strains, named H9, H18, H51, H61, H77 and H108. The antimicrobial activity of crude bacteriocin extracts from these strains was completely inactivated after proteinase K and trypsin treatment, heat-labile but relatively stable at pH 4-10. Sequencing and phylogenetic analysis of the 16S rRNA and rpoB genes resulted in the identification of one strain (H77) as Enterobacter cloacae and the other strains as Cronobacter sakazakii. This is the first evidence of bacteriocins produced by a member of the genus Cronobacter and also by bacteria associated with clam. The research presents data that support further studies of bacteriocin diversity in marine bacteria and their potential as probiotics or antibiotic substitutes for sustainable aquaculture.