Abstract
The 8th Symposium on Lactic Acid Bacteria (LAB) held in August 2005 in Egmond aan Zee, The Netherlands (), was again the largest meeting of its kind, bringing together 700 scientists from academia and industry around the world to discuss genetics, metabolism and applications in bioprocessing and health of these industrially important bacteria. One of the most striking advances demonstrated at this event was the explosion in the characterization of the genomes of LAB and their genetic elements.
Lactic acid bacteria (LAB) are a heterogeneous family of mainly low G+C Gram-positive, anaerobic, non-sporulating and acid-tolerant bacteria. They can ferment various nutrients in a homofermentative or heterofermentative fashion into primarily lactic acid, but also into by-products such as acetic acid, formic acid, ethanol and carbon dioxide. They contribute to rapid acidification of food products, but also to flavour, texture and nutrition. Lactic acid bacteria are naturally found in plant, meat, dairy and cereal fermentation environments, and have a long tradition of use in industrial and artisan food and feed fermentations, where they are used as starter cultures for fermenting raw materials of vegetable or animal origin.
More recently, it has been recognized that some LAB and high G+C Gram-positive bifidobacteria are natural inhabitants of the human and animal gastro-intestinal tract, where they contribute to and stimulate gastro-intestinal health (Vaughan et al., 2005). This probiotic (health-promoting) activity is now being exploited by enriching functional foods and drinks with probiotic LAB, mainly lactobacilli and bifidobacteria (Saxelin et al., 2005). Emphasis in scientific research of LAB has shifted towards unravelling and understanding the mechanisms of probiotic effects, and survival and colonization of LAB in the gastro-intestinal tract as this evidence is required to substantiate health claims of commercial probiotic products.
Genome sequencing of food and health-related LAB and bifidobacteria was slow to start, as only Lactococcus lactis IL1403 (Bolotin et al., 2001) and Bifidobacterium longum NCC2705 (Schell et al., 2002) were published at the time of the 7th Symposium on Lactic Acid Bacteria in 2002, shortly followed by the largest known LAB genome to date, Lactobacillus plantarum WCFS1 (Kleerebezem et al., 2003). High hopes for rapid up-scaling were expressed at that time, since many genome projects worldwide were in the pipeline (Klaenhammer et al., 2002), including the sequencing of 11 LAB genomes by the Joint Genome Institute (), initiated by the LAB Genomics Consortium in the USA. Now, at the 8th LAB Symposium in 2005, the keynote lecturer (Klaenhammer et al., 2005) showed that the published genome sequences of Lactobacillus johnsonii (Pridmore et al., 2004), Lactobacillus acidophilus (Altermann et al., 2005) and two Streptococcus thermophilus strains (Bolotin et al., 2004) and whole LAB genome comparisons (Boekhorst et al., 2004) have been added to this list (Table 1). But the real state-of-the-art was evident from oral presentations and numerous posters (abstracts at ), describing genome sequencing of about 30 LAB and bifidobacteria strains (Table 1). In fact, many of these genome sequences are now complete and in the process of annotation or being submitted for publication, as is the case for the JGI genomes (Klaenhammer et al., 2005). Sequencing of large LAB plasmids, known to encode important traits and provide competitive advantage to parent strains, was also reported (Siezen et al., 2005).