Project description:The contribution of small RNAs to the regulation of cell wall defense mechanisms, which play a central role in protecting bacteria from environmental insults, remains poorly understood in Lactococcus cremoris, a paradigmatic organism for studying lactic acid bacteria. Analysis of the profiles of 193 putative sRNAs, including 131 newly identified in this study, revealed altered expression of 20 and 25 sRNAs following treatment with major cell wall-targeting antimicrobials lysozyme and penicillin G, respectively. Further analysis and genome-wide functional screening identified four sRNAs that modulate the lysozyme response in opposite directions, with sLLM1042+, sLLM2-, and sLLM1993+ conferring increased, and sLLM461+ decreased, resistance. Moreover, elevated expression of sLLM2- or sLLM1042+ promoted the sensitivity of cells to penicillin G and certain abiotic stresses, and had pleiotropic effects on gene regulation at both RNA and protein levels, positioning them as key elements in regulatory networks. Notably, the sLLM2- mediated decrease in four putative tellurium resistance proteins resulted in L. cremoris sensitivity to tellurite stress. As sLLM2- mutations, altering lysozyme and penicillin responses, reduce the expression of alanine racemase Alr, we suggest that its upregulation possibly modulates D-alanine levels, thereby affecting lipoteichoic acid modification or peptidoglycan synthesis. Our findings underscored the broad roles of sRNAs in defensive responses to cell wall-targeting antimicrobials in lactic acid bacteria.

2026-04-13 | GSE299211 | GEO

SpxB regulates O-acetylation dependent resistance of Lactococcus lactis peptidoglycan to hydrolysis

Project description:Endogenous peptidoglycan (PG) hydrolysing enzymes, the autolysins, are needed to relax the rigid PG sacculus to allow bacterial cell growth and separation. PG of pathogens and commensal bacteria may also be degraded by hydrolases of animal origin (lysozymes), which act as antimicrobials. The genetic mechanisms regulating PG resistance to hydrolytic degradation was dissected in the Gram-positive bacterium Lactococcus lactis. We found that the ability of L. lactis to counteract PG hydrolysis depends on the degree of acetylation. Overexpression of PG O-acetylase, encoded by oatA, led to bacterial growth arrest, indicating potential lethality of oatA and a need for its tight regulation. A novel regulatory factor SpxB (previously denoted as YneH), exerts a positive effect on oatA expression. Our results indicate that SpxB binding to RNA polymerase constitutes a previously missing link in the multi-step response to cell envelope stress, provoked by PG hydrolysis with lysozyme. We suggest that the two component system CesSR responds to this stress by inducing SpxB, thus favoring its interactions with RNA polymerase. Induction of PG O-acetylation by this cascade renders it resistant to hydrolysis. Keywords: mutant, lysozym

2007-04-17 | GSE7386 | GEO

Lactococcus lactis MG1363 â??guaA versus L. lactis MG1363 (wt)

Project description:Gene expression in Lactococcus lactis MG1363 was compared to that of L. lactis MG1363 â??guaA in rich GM17 medium. One condition design comparison of two strains

2016-01-12 | E-GEOD-76764 | biostudies-arrayexpress

Lactococcus cremoris subsp. cremoris MG1363

Project description:Analysis of the effect of acid stress in Lactococcus lactis MG1363

| PRJNA203275 | ENA