AUTHOR=Delpech Pierre , Rifa Etienne , Ball Graham , Nidelet Sabine , Dubois Emeric , Gagne Geneviève , Montel Marie-Christine , Delbès Céline , Bornes Stéphanie 

TITLE=New Insights into the Anti-pathogenic Potential of Lactococcus garvieae against Staphylococcus aureus Based on RNA Sequencing Profiling

JOURNAL=Frontiers in Microbiology

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2017.00359

DOI=10.3389/fmicb.2017.00359

ISSN=1664-302X

ABSTRACT=<p>The bio-preservation potential of <italic>Lactococcus garvieae</italic> lies in its capacity to inhibit the growth of <italic>staphylococci</italic>, especially <italic>Staphylococcus aureus</italic>, in dairy products and <italic>in vitro</italic>. <italic>In vitro</italic>, inhibition is modulated by the level of aeration, owing to hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) production by <italic>L. garvieae</italic> under aeration. The <italic>S. aureus</italic> response to this inhibition has already been studied. However, the molecular mechanisms of <italic>L. garvieae</italic> underlying the antagonism against <italic>S. aureus</italic> have never been explored. This study provides evidence of the presence of another extracellular inhibition effector <italic>in vitro</italic>. This effector was neither a protein, nor a lipid, nor a polysaccharide, nor related to an L-threonine deficiency. To better understand the H<sub>2</sub>O<sub>2</sub>-related inhibition mechanism at the transcriptome level and to identify other mechanisms potentially involved, we used RNA sequencing to determine the transcriptome response of <italic>L. garvieae</italic> to different aeration levels and to the presence or absence of <italic>S. aureus</italic>. The <italic>L. garvieae</italic> transcriptome differed radically between different aeration levels mainly in biological processes related to fundamental functions and nutritional adaptation. The transcriptomic response of <italic>L. garvieae</italic> to aeration level differed according to the presence or absence of <italic>S. aureus</italic>. The higher concentration of H<sub>2</sub>O<sub>2</sub> with high aeration was not associated with a higher expression of <italic>L. garvieae</italic> H<sub>2</sub>O<sub>2</sub>-synthesis genes (<italic>pox</italic>, <italic>sodA</italic>, and <italic>spxA1</italic>) but rather with a repression of <italic>L. garvieae</italic> H<sub>2</sub>O<sub>2</sub>-degradation genes (<italic>trxB1</italic>, <italic>ahpC</italic>, <italic>ahpF</italic>, and <italic>gpx</italic>). We showed that <italic>L. garvieae</italic> displayed an original, previously undiscovered, H<sub>2</sub>O<sub>2</sub> production regulation mechanism among bacteria. In addition to the key factor H<sub>2</sub>O<sub>2</sub>, the involvement of another extracellular effector in the antagonism against <italic>S. aureus</italic> was shown. Future studies should explore the relation between H<sub>2</sub>O<sub>2</sub>-metabolism, H<sub>2</sub>O<sub>2</sub>-producing LAB and the pathogen they inhibit. The nature of the other extracellular effector should also be determined.</p>