Genomic and proteomic characterization of bacteriocin-producing Leuconostoc mesenteroides strains isolated from raw camel milk in two southwest Algerian arid zones

Abstract

Information on the microbiology of camel milk is very limited. In this work, the genetic characterization and proteomic identification of 13 putative producing bacteriocin Leuconostoc strains exhibiting antilisterial activity and isolated from camel milk were performed. DNA sequencing of the 13 selected strains revealed high homology among the 16S rRNA genes for all strains. In addition, 99% homology with Leuconostoc mesenteroides was observed when these sequences were analysed by the BLAST tool against other sequences from reference strains deposited in the Genbank. Furthermore, the isolates were characterized by matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDITOF MS) which allowed for the identification of 2 mass peaks 6242 m/z and 5118 m/z that resulted to be specific to the species L. mesenteroides. Remarkably, the phyloproteomic tree provided more intraspecific information of L. mesenteroides than phylogenetic analysis. Accordingly, phyloproteomic analysis grouped L. mesenteroides strains into different subbranches, while all L. mesenteroides isolates were grouped in the same branch according to phylogenetic analysis. This study represents, to our knowledge, the first report on the use of MALDI-TOF MS on the identification of LAB isolated from camel milk.

Figure 1

Antibacterial activity after eliminating lactic acid with buffered medium. (a) Leuconostoc mesenteroides effect on Listeria innocua. (b) Leuconostoc mesenteroides effect on Listeria ivanovii. Z1–Z6: L. mesenteroides isolated from camel milk sample 1 and B7: L. mesenteroides isolated from camel milk sample 2.

Figure 2

Phylogenetic tree of Leuconostoc spp. This tree was generated for Leuconostoc spp. isolated from camel milk and other reference strains based on 16S rRNA nucleotide sequences using the neighbour-joining method. Numbers above and below branches indicate bootstrap values from the neighbour-joining analysis.

Figure 3

Characteristic mass peaks of L. mesenteroides strain Z_2-09 isolated from camel milk. Specific genus peaks marked as (∗) are present in other Leuconostoc strains and peaks marked as (▼) are absent in the Lactococcus genus.

Figure 4

Spectra corresponding to the species L. carnosum, L. mesenteroides, and L. pseudomesenteroides. Species-specific peaks are marked in each case by (▽).

Figure 5

Phyloproteomic tree of Leuconostoc spp. based on the protein profile obtained by MALDI-TOF MS.