Whole-genome sequencing of Pseudoalteromonas piscicida 2515 revealed its antibacterial potency against Vibrio anguillarum: a preliminary invitro study

Abstract

Pseudoalteromonas piscicida 2515, isolated from Litopenaeus vannamei culture water, is a potential marine probiotic with broad anti-Vibrio properties. However, genomic information on P. piscicida 2515 isscarce. In this study, the general genomic characteristics and probiotic properties of the P. piscicida 2515 strain were analysed. In addition, we determined the antibacterial mechanism of this bacterial strain by scanning electron microscopy (SEM). The results indicated that the whole-genome sequence of P. piscicida 2515 contained one chromosome and one plasmid, including a total length of 5,541,406 bp with a G+C content of 43.24%, and 4679 protein-coding genes were predicted. Various adhesion-related genes, amino acid and vitamin metabolism and biosynthesis genes, and stress-responsive genes were found with genome mining tools. The presence of genes encoding chitin, bromocyclic peptides, lantibiotics, and sactipeptides showed the strong antibacterial activity of the P. piscicida 2515 strain. Moreover, in coculture with Vibrio anguillarum, P. piscicida 2515 displayed vesicle/pilus-like structures located on its surface that participated in its bactericidal activity, representing a novel antibacterial mechanism. Nevertheless, 16 haemolytic genes and 3 antibiotic resistance genes (tetracycline, uoroquinolone, and carbapenem) were annotated, but virulence genes encoding enterotoxin FM (entFM), cereulide (ces), and cytotoxin K were not detected. Further toxicity tests should be conducted to con rm the safety of P. piscicida 2515. The results here provide a new understanding of the probiotic properties and antibacterial mechanism of P. piscicida 2515 and theoretical information for its application in aquaculture.