Strategies to improve the phage resistance of lactic acid bacteria (lab)

Abstract

Phage infections of lactic acid bacteria used in the fermentative dairy industry are the principal cause of failures in their acidifying activity. In the last 25 years, a priority of research in this area was the development of phage resistant cultures with good technological capacity for industrial uses. Different strategies have been used to improve LAB strains: 1) Recombinant DNA techniques (Per, Antisense RNA and Suicide system). These were developed mainly for lactococci and turned out highly efficient but very specific against phages. Anyway, these genetically modified strains cannot be used for foods. 2) Transfer of phage resistance determinants by conjugation. This method has been very used in many countries to obtain industrial strains, and 3) Isolation of spontaneous phage resistant mutants (from secondary cultures or flow cytometry). This is a “natural” strategy and, so, allows to obtain “food grade” strains. Furthermore, it is a simple and rapid method, excepting for the cytometric alternative that requires a specific and expensive equipment.