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We propose a new method that allows accurate discrimination of Lactobacillus helveticus from other closely related homofermentative lactobacilli, especially Lactobacillus gallinarum. This method is based on the amplification by PCR of two peptidoglycan hydrolytic genes, Lhv_0190 and Lhv_0191. These genes are ubiquitous and show high homology at the intra-species level. The PCR method gave two specific PCR products, of 542 and 747 bp, for 25 L. helveticus strains coming from various sources. For L. gallinarum, two amplicons were obtained, the specific 542 bp amplicon and another one with a size greater than 1,500 bp. No specific PCR products were obtained for 12 other closely related species of lactobacilli, including the L. acidophilus complex, L. delbrueckii, and L. ultunensis. The developed PCR method provided rapid, precise, and easy identification of L. helveticus. Moreover, it enabled differentiation between the two closely phylogenetically related species L. helveticus and L. gallinarum.

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Solichová K., Složilová I., Jebavá I., Uhrová B., Plocková M. (2012): Characterisation of antilisterial bacteriocin-like substance produced by Enterococcus mundtii. Czech J. Food Sci., 30: 89-97.The antilisterial activity of e. mundtii 1282 strain and its cell-free neutralised supernatant was observed against five persistent l. monocytogenes strains using the agar spot method. The enterococcal metabolite was consequently characterised as a proteinaceous substance -the bacteriocin-like substance, which was heat-stable at heating to 100°C for 30 min, stable at pH 2-12, and still active after eight-week long storage at 6°C and -20°C. The bacteriocin-like substance reached the highest activity of 6400 AU/ml after ten hours of cultivation of e. mundtii 1282 strain, when it was at the stationary phase of its growth. e. mundtii 1282 strain produced the bacteriocin-like substance: in BHI broth with pH 4-6, at the cultivation temperature 12-45°C, and in BHI broth with 1-6% (w/w) NaCl.