Two different propionicins produced by Propionibacterium thoenii P-127

The bacteriocin GBZ-1 was purified from the growth media of Propionibacterium thoenii P-127 and was found to have a molecular weight of 6000 Da. P. thoenii P-127 also known as the producer of the bacteriocin PLG-1 (MW 10 kDa). Under specific growth conditions, on semi-solid media, P. thoenii P-127 produced both PLG-1 and GBZ-1. The N-terminal of GBZ-1 was microsequenced, the gene was cloned and the DNA sequence was determined and identified. GBZ-1 is highly homologous to a protease-activated antimicrobial peptide (PAMP). In contrast to PAMP, it was purified in its active form and no protease digestion was required for its activation. The survival curve of indicator bacteria Lactobacillus delbrueckii subsp. lactic ATCC 4797 showed two phases. The fast phase of 20 min was followed by a slow phase. While bacterial survival was reduced by 2 logs during the fast phase, bacterial survival was reduced by additional 3 logs up to 200 min during the slow phase. GBZ-1 activity was affected by magnesium and its activity was completely abolished at 50 mM magnesium chloride. Other divalent cations had no effect on GBZ-1 activity of GBZ-1. To the best of our knowledge this is the first report of a bacterium producing two different bacteriocins under different growth conditions.