Serine and threonine activate Ser/Thr kinase gene to increase the density of Lactobacillus bulgaricus sp1.1 under salt stress

Résumé fourni par la source

Salt stress significantly impedes high cell-density culture by suppressing the reproductive capacity of lactic acid bacteria . This study examined the effects of salt stress conditions (2% w/v NaCl) on Lactobacillus bulgaricus sp1.1. Although DNA replication and division ring localization remained unaffected, the down-regulation of the ftsZ and dnaA genes inhibited division ring assembly. Consequently, bacteria exhibited filamentation , increased cell length, and accumulated chromosomes and division rings, which obstructed cell division. Under salt stress, sp1.1 experienced several transcriptional changes. The serine/threonine kinase gene was identified as a significant regulator of bacterial division under salt stress. Exogenous addition of serine and threonine could stimulate the expression of Ser/Thr kinase gene, promote the assembly of division ring, and enhance the dividing ability of the bacterium, which led to a density of 7.93 log CFU/mL under the salt stress, which was 6.92 times higher than that of the untreated group. This study provides a new perspective for high-density cultivation of lactic acid bacteria .

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