In both systems, the bacteriocin activity decreased more quickly in the presence of wt than in the presence of LMGel, i.e. 24 h sooner in the broth culture and 1 week sooner in the meat system. In broth, strain LMG grew fastest (μmax=0.52), followed by LMGel (0.32) and finally wt (0.22). As the bacteriocin level increased initially at the same rate and reached the same peak value in the LMGel and wt cultures,

it would seem that LMGel is a somewhat less efficient bacteriocin producer than wt, possibly because of plasmid instability. As expected, bacteriocin-degrading proteolytic activity remained low (at about 7.5 U mL−1) in broth cultures seeded with LMG or Autophagy Compound Library cell line LMGel. In cultures seeded with wt or mt, it was about twice as high at the start of the culture and seven times as high at the end. Here, we demonstrate that sakacin P production in L. curvatus is encoded by a plasmid. This is clear from the nonbacteriocinogenic phenotype of our plasmid-cured mutants, from binding of a sakacin-specific probe to plasmid restriction fragments on Southern blots, and from binding of the same

probe to the amplicon produced by PCR from gel-purified plasmid DNA. This approximately 10-kb plasmid, furthermore, appears to exist in two different forms and additionally Y-27632 price to confer streptomycin resistance and the ability to ferment d-celobiose, gentiobiose, and N-acetylglucosamine. These extra features facilitate selection of plasmid-containing cells (with streptomycin) or offer a means of enhancing plasmid

stability (using carbohydrates that can be fermented only if the plasmid is present). Plasmids associated with bacteriocin production, antibiotic resistance, and/or metabolic traits are common in lactobacilli (reviewed in Wang & Lee, 1997). Sometimes, the bacteriocin-encoding plasmid http://www.selleck.co.jp/products/Docetaxel(Taxotere).html also carries a gene conferring immunity to the bacteriocin concerned, and plasmid loss results in sensitivity to that bacteriocin (Møretrøet al., 2005). Here, our plasmid-cured mt isolates remained resistant to sakacin P (plate assays and high-titre exposure, data not shown). This contrasts with the situation described by Møretrøet al. (2005). Naturally occurring LAB have long been used in food technology, and the use of genetically engineered LAB with improved features is envisaged for many applications. In the European Union, regulation EC1829/2003 prohibits the use of genetically modified organisms in human food unless the proposed use has been approved on the basis of evidence that it is safe for human health, animal health, and the environment and that it neither misleads the consumer nor diminishes the nutritional quality of the food. This regulation is applicable to strain LMGel. Regarding the safety of this strain, it is worth stressing that this is genetic engineering performed between two LAB strains of the same genus that are suitable for use in food.

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