New Insights into the Anti-pathogenic Potential of against Based on RNA Sequencing Profiling.

The bio-preservation potential of lies in its capacity to inhibit the growth of , especially , in dairy products and . , inhibition is modulated by the level of aeration, owing to hydrogen peroxide (HO) production by under aeration. The response to this inhibition has already been studied. However, the molecular mechanisms of underlying the antagonism against have never been explored. This study provides evidence of the presence of another extracellular inhibition effector . This effector was neither a protein, nor a lipid, nor a polysaccharide, nor related to an L-threonine deficiency. To better understand the HO-related inhibition mechanism at the transcriptome level and to identify other mechanisms potentially involved, we used RNA sequencing to determine the transcriptome response of to different aeration levels and to the presence or absence of . The transcriptome differed radically between different aeration levels mainly in biological processes related to fundamental functions and nutritional adaptation. The transcriptomic response of to aeration level differed according to the presence or absence of . The higher concentration of HO with high aeration was not associated with a higher expression of HO-synthesis genes (, , and ) but rather with a repression of HO-degradation genes (, , , and ). We showed that displayed an original, previously undiscovered, HO production regulation mechanism among bacteria. In addition to the key factor HO, the involvement of another extracellular effector in the antagonism against was shown. Future studies should explore the relation between HO-metabolism, HO-producing LAB and the pathogen they inhibit. The nature of the other extracellular effector should also be determined.