Biodiversity of the antimicrobial potential of Weissella paramesenteroides strains isolated from dairy cattle

Weissella species are lactic acid bacteria with a high potential for the fermentation of food items. They ferment fruits, vegetables, fish, and meat to deliver aromatic ingredients, produce antibacterial and antifungal compounds, and exert probiotic properties. Despite these attractive attributions, they are still poorly studied. We have isolated 40 strains of Weissella paramesenteroides from one biotope, the udder of milk cattle, to examine genomic plasticity, antibacterial efficacy, and organic acid and hydrogen peroxide formation. Each isolate was identified by DNA sequence comparisons of the 16S rRNA-encoding gene. Patterns of genomic DNA fragments from random amplification of polymorphic DNA showed that 38 isolates differed by more than 5%, thus representing subspecies. Nine isolates were selected for further characterization. They were able to inhibit all eight food-borne pathogens and surrogates used. Salmonella enterica and Pseudomonas aeruginosa were strongly inhibited, while inhibition of Listeria monocytogenes was weaker but still significant. However, the inhibition profiles varied considerably. Acid production was assessed for each isolate in the presence of indicator strains exhibiting different acidification patterns as well. The presence of S. enterica was associated with a drop in pH, whereas no notable acidification occurred when isolates were challenged with Klebsiella pneumoniae and Bacillus subtilis . To confirm the observed differences, we analyzed the pan-genomes of 10 genomes retrieved from the NCBI database. Each genome contains several 100 accessory genes and up to 6.5% unique genes, indicating a high genome fluidity and additional strain-specific metabolic capacity. We suggest that the antibacterial efficacy of W. paramesenteroides is based on a multi-barrier system, whereby strains have developed different genetic qualities for the expression of an individual set of barriers.