Abstract
Probiotics are a viable alternative to traditional chemotherapy agents to control infectious diseases in aquaculture. In this regard, Lactococcus lactis subsp. cremoris WA2-67 has previously demonstrated several probiotic features, such as a strong antimicrobial activity against ichthyopathogens, survival in freshwater, resistance to fish bile and low pH, and hydrophobicity. The aim of this manuscript is an in silico analysis of the whole-genome sequence (WGS) of this strain to gain deeper insights into its probiotic properties and their genetic basis. Genomic DNA was purified, and libraries prepared for Illumina sequencing. After trimming and assembly, resulting contigs were subjected to bioinformatic analyses. The draft genome of L. cremoris WA2-67 consists of 30 contigs (2,573,139 bp), and a total number of 2493 coding DNA sequences (CDSs). Via in silico analysis, the bacteriocinogenic genetic clusters encoding the lantibiotic nisin Z (NisZ) and two new bacteriocins were identified, in addition to several probiotic traits, such as the production of vitamins, amino acids, adhesion/aggregation, and stress resistance factors, as well as the absence of transferable antibiotic resistance determinants and genes encoding detrimental enzymatic activities and virulence factors. These results unveil diverse beneficial properties that support the use of L. cremoris WA2-67 as a probiotic for aquaculture.
Highlights
Amongst the probiotic traits, analyzed through RAST, were putative genes involved in adhesion and aggregation, vitamin biosynthesis, amino acids metabolism, production of lactic acid, active metabolism, enzyme production involved in food digestion, and stress and host gastro-intestinal tract adaptation (Table S1)
The by which nisin-producing strains protect themselves against the toxicity of their leader peptide is cleaved off by a cell-membrane anchored subtilisin-like protease own bacteriocin: (i) the lipoprotein encoded by nisI, and (ii) the ATP-binding cassette (ABC) transporter encoded by nisP, and resulting in the mature and biologically active nisin Z (NisZ) [71,73]
By NisZ, which consists of apreviously sensor histidine kinase response regulator, encoded we have demonstrated thatand the aknockout isogenic mutant strain L. by cremoris nisK and nisR, respectively
Summary
There are no specific guidelines for the evaluation and selection of probiotics intended for aquaculture, there are general recommendations for their evaluation These recommendations are based upon safety assessments of microorganisms, both used in food and feed, taxonomical identification, and for instance, resistance to antibiotics of clinical importance for human medicine. Bacteriocin production is a common trait of LAB, and many bacteriocinogenic strains have been characterized, displaying antimicrobial activity against a wide range of Gram-positive bacteria, and, to a lesser extent, Gram-negative bacteria, including spoilage and foodborne pathogens Their spectrum of antimicrobial activity has attracted great interest for their potential as food preservatives and as therapeutical agents in both human and veterinary medicine [13]. We performed in silico analysis through use of diverse databases, tools, and software [17–20]
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