ABSTRACT
Resorting to mutagenesis permits creating artificial variability, thus increasing the possibilities of choice. However, mutagenic agents often cause undesirable mutations which can reduce the competitiveness of the strains in a hostile environment. Techniques of genetic engineering henceforth allow for envisioning traumatic modifications of the genome. The field of variability can be considerably enlarged by resorting to genes identified in other groups of microorganisms.
