Abstract
Lactic acid bacteria (LAB) are important organisms in food production. Indeed, LAB autolysis is very critical in dairy processing. For example, it influences the development of cheese flavor by releasing intracellular enzymes, and controls cell growth in yogurts and probiotic products. Two component systems (TCS) constitute essential environmental sensors and effectors of signal transduction in most bacteria. In the present work, mutants of one TCS (LBUL_RS00115/LBUL_RS00110) were generated to assess the relationship between TCS and cell autolysis. The mutants displayed decreased autolysis in comparison with wild type; meanwhile, complementation reversed this effect. The interaction between LBUL_RS00115 and LBUL_RS00110 was confirmed by yeast two-hybrid analysis. These observations suggested that the TCS (LBUL_RS00115/LBUL_RS00110) was involved in autolysis in Lactobacillus delbrueckii subsp. bulgaricus.
Highlights
Lactic acid bacteria (LAB) are common starters for the production of yogurt and other dairy products, and their autolysis attracts increasing attention (Cibik and Chapot-Chartier, 2000; Ouzari et al, 2002; Ortakci et al, 2015)
In order to verify whether there is a correlation between the two Two component systems (TCS) and cell autolysis, LBUL_RS04160 and LBUL_RS00115 were knocked out, respectively
Previous research in our laboratory demonstrated that N-acetylmuramidase has a critical function in L. bulgaricus autolysis (Pang et al, 2014), as one of the major degraders of the cell wall
Summary
Lactic acid bacteria (LAB) are common starters for the production of yogurt and other dairy products, and their autolysis attracts increasing attention (Cibik and Chapot-Chartier, 2000; Ouzari et al, 2002; Ortakci et al, 2015). Starter strain lysis in the ripening step releases cytoplasmic enzymes that degrade amino acids into cheese (Xu and Kong, 2013). Such enzymes are believed to promote the degradation of peptides, removing the bitter ones (Valence et al, 2000; Collins et al, 2003; Visweswaran et al, 2017). LAB autolysis lowers live cell count of starters (Pang et al, 2014). This demonstrates the significant role of LAB autolysis in food production, and unveiling the underlying mechanisms is of prime importance
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