Antimicrobial Activity of Lactococcus lactis subsp. lactis Isolated from a Stranded Cuvier's Beaked Whale (Ziphius cavirostris) against Gram-Positive and -Negative Bacteria.

Akihiko Suzuki,Miwa Suzuki

doi:10.3390/microorganisms9020243

Abstract

In the present study, we isolated and characterized Lactococcus lactis (L. lactis) subsp. lactis from a female Cuvier’s beaked whale (Ziphius cavirostris) stranded in Shizuoka, Japan. Only five isolates (CBW1-5), grown on Lactobacilli de Man Rogosa Sharpe (MRS) agar plates prepared using 50% artificial seawater, were positive in L. lactis species-specific primer PCR. Their 16S rRNA sequences were highly similar to those of L. lactis subsp. lactis JCM 5805T. The Gram reaction, motility, gas production from glucose, catalase production, and growth conditions were consistent with those of the type strain. Additionally, carbohydrate utilization of the strains was consistent with previously reported marine organism-derived strains. The pH-neutralized cell-free culture supernatant of strain CBW2 inhibited the growth of Bacillus subtilis subsp. subtilis ATCC 6051 and Vibrio alginolyticus ATCC 17749, whereas protease treatment eliminated or diminished its inhibitory activity. The strain possesses a precursor of the nisin structural gene (nisA), which showed 100% homology with nisin Z, and nisin biosynthesis-related genes (nisB, nisC, nisT, nisP, nisF, nisI, and nisRK), suggesting that the strain produces a nisin-like substance. This study provides fundamental information on whale-derived L. lactis subsp. lactis which may be useful for reducing the carriage of B. subtilis subsp. subtilis and V. alginolyticus.

Highlights

Some strains of lactic acid bacteria (LAB), such as Enterococcus, Lactobacillus, Lactococcus, and Pediococcus, have received attention as beneficial organisms [1]
Lactis JCM 5805T (99.04–99.93% similarity) (Table 4). These strains were clustered in the same group as L. lactis subsp. lactis using the neighbor-joining method and Kimura’s two-parameter model, with 100% bootstrap values based on 1000 replicates (Figure 1)
We found that strain CBW2 possessed nisin biosynthesisrelated gene, nisBTCIPRK, and a nisin immunity-related gene, nisF, which is a part of the downstream nisFEG operon

Summary

Introduction

Some strains of lactic acid bacteria (LAB), such as Enterococcus, Lactobacillus, Lactococcus, and Pediococcus, have received attention as beneficial organisms [1]. LAB create a lowpH environment, by fermenting several nutrients, and produce antimicrobial factors, which can prevent contamination by pathogenic bacteria [1,2]. The interaction between LAB and the intestinal mucosa of the host is associated with immunostimulating and immunomodulatory effects [3]. Many studies have reported the potential benefits of using various LAB strains in the food industry [4,5] and LAB-associated health improvement in animals and humans [6,7,8]. Bacteriocins are gene-encoded, ribosomally-synthesized antimicrobial peptides produced by both Gram-positive and -negative microorganisms [9].

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