Purpose: The objective of this work is to evaluate genotypic and phenotypic biodiversity of this species by working on strains mainly isolated in the dairy industry but also foodborne strains from outside the dairy ecosystem as well as collections or epidemic strains. A better understanding of this diversity will allow better assessment of the spoilage risks linked to this microorganism.
Methods: More than sixty strains were studied by molecular methods: mainly PFGE and PCR based clustering analysis (REP PCR, M13 RAPD). Among these strains, about thirty were studied for their ability to produce biofilm, surfactant and different enzymes (gelatinase, caseinase, amylase and lipoprotease). All manipulations were performed at least in duplicate and the average result is used for further processing. Clusters of strains were made primarily by hierarchical clustering (Bionumerics, Minitab and JMP)
Results: Composite molecular fingerprint analysis generated by Bionumerix underlined a major group composed of the type strain, raw materials, environment and most dairy product isolates. In order to complete the picture of the potential risks, the combination of molecular and phenotypic diversity yields to a more diverse clustering. Even though in minority, a few strains were distinguished by their high potential for spoilage and/or biofilm formation.
Significance: These results underline the large diversity of strains of B. licheniformis encountered in dairy ecosystem as compared to strains from other origins. The study highlights the existence of clusters with similar behaviors or characteristics but also of more atypical strains that could be considered as “super spoilers.”