Lactic Acid Bacteria: Genomics, Genetic Engineering

Lactic acid bacteria (LAB) consist of a phylogenetically related group of bacteria that share a common reliance on fermentation with lactic acid as the major end product. Bifidobacteria are phylogenetically distinct, but share many phenotypic characteristics, including a reliance on fermentation with lactic acid as the major end product, and are therefore often included with the LAB. The economic significance of this group of bacteria in the food fermentation and probiotic (ingesting microbes for intestinal and overall health) industries has prompted extensive research. Numerous genetic tools for manipulating these bacteria have been developed, including cloning vectors, vectors for heterologous gene expression, and strategies for site-directed mutagenesis and gene replacement. Representatives of most of the species comprising this group of organisms have also been sequenced completely and their genomes reflect their evolutionary background. It is evident from a comparative genome analysis of the LAB that their evolution involved significant genome reduction during adaptation to their nutrient habitats and involved acquiring a large array of transporters to facilitate utilizing the varied nutrients from their environments. This genome analysis is furthering the understanding of this very intriguing group of organisms that impact the lives of every person on the planet.