Genetics of Lactic Acid Bacteria

Many meat (or fish) products, obtained by the fermentation of meat originating from various animals by the flora that naturally contaminates it, are part of the human diet since millenaries. Historically, the use of bacteria as starters for the fermentation of meat, to produce dry sausages, was thus performed empirically through the endogenous micro-biota, then, by a volunteer addition of starters, often performed by back-slopping, without knowing precisely the microbial species involved. It is only since about 50 years that well defined bacterial cultures have been used as starters for the fermentation of dry sausages. Nowadays, the indigenous micro-biota of fermented meat products is well identified, and the literature is rich of reports on the identification of lactic acid bacteria (LAB) present in many traditional fermented products from various geographical origin, obtained without the addition of commercial starters (See Talon, Leroy, & Lebert, 2007, and references therein). The LAB species that are naturally present in those products and become dominant in the final processing steps essentially belong to Lactobacillus sakei, Lactobacillus curvatus, and Lactobacillus plantarum. These are also the three main species that are sold as starters for the fermentation of dry sausages, essentially in Europe, to which should be added the two other pediococci species Pediococcus pentosaceus and Pediococcus acidilactici (Hammes & Hertel, 1998). Since the last 20 years, many microbiologists have investigated the physiology of these LAB, in order to understand the mechanisms by which they contribute to the quality of the final product, and to improve their use. Molecular tools were therefore developed, leading to an increase of the knowledge about their genetics. More recently, the genomes of L. plantarum WCFS1 (Kleerebezem, et al, 2003), L. sakei 23K (Chaillou, et al., 2005), and P. pentosaceus ATCC25745 (Makarova, et al., 2006) were entirely sequenced, giving a general overview on the whole genetic repertoire of those bacteria. However, the description and analysis of all