GENETICS AND EVALUATION OF THE INDUSTRIAL POTENTIAL OF LACTIC-ACID BACTERIA

The technological properties of a strain which influence the manufacturing process and the quality of the product is the result of the expression and regulation of a great number of genes. Such complexity impedes the development of direct genetic measures of the industrial potential of strains. Moreover, the biochemical analysis of products is not yet reliable. The only available method to evaluate the quality of a strain is thus to use it for small-scale production, which is time-consuming and thus limited to a restricted number of strains. The rapid development of molecular biology might alleviate this problem. Although a very limited number of characters can be detected by these methods, molecular taxonomy leads to the classification of strains into genetically related species, subspecies, groups and subgroups which share a number of properties. The construction of a phylogenic tree with different clones of a species would allow a more rational choice of the strains to be tested. The study of polymorphism by RFLP, PFGE, PCR and nucleotide sequences of strains from the genus Lactococcus gives a first view of the genetic diversity of lactococcal strains isolated from dairy PrOducts and from some other biotopes. The 2 subspecies L lactis subsp lactis and L lactis subsp cremoris which can not be properly discriminated by phenotypical tests are not closely related genetically. Their nucleotide sequences diverge by 15 to 20 %. Two subspecies probes have been developed to distinguish them unambiguously. Within a subspecies, some groups can be differentiated and the nucleotide sequence of some clones allowed a direct measure of their relatedness. The maximum divergence detected was 3 %. The systematic use of these methods followed by statistical analysis of the data would improve our knowledge on the genetic potential in a species and enable a rational approach for the selection of the strains to be established.