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

The technological properties of a strain which influence the manufactu ring process and the quality of the product is the result of the expre ssion and regulation of a great number of genes. Such complexity imped es the development of direct genetic measures of the industrial potent ial of strains. Moreover, the biochemical analysis of products is not yet reliable. The only available method to evaluate the quality of a s train is thus to use it for small-scale production, which is time-cons uming and thus limited to a restricted number of strains. The rapid de velopment 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 genetic ally related species, subspecies, groups and subgroups which share a n umber of properties. The construction of a phylogenic tree with differ ent clones of a species would allow a more rational choice of the stra ins to be tested. The study of polymorphism by RFLP, PFGE, PCR and nuc leotide sequences of strains from the genus Lactococcus gives a first view of the genetic diversity of lactococcal strains isolated from dai ry PrOducts and from some other biotopes. The 2 subspecies L lactis su bsp lactis and L lactis subsp cremoris which can not be properly discr iminated by phenotypical tests are not closely related genetically. Th eir nucleotide sequences diverge by 15 to 20 %. Two subspecies probes have been developed to distinguish them unambiguously. Within a subspe cies, some groups can be differentiated and the nucleotide sequence of some clones allowed a direct measure of their relatedness. The maximu m divergence detected was 3 %. The systematic use of these methods fol lowed by statistical analysis of the data would improve our knowledge on the genetic potential in a species and enable a rational approach f or the selection of the strains to be established.