AUTHOR=Gaio Vânia , Lima Tânia , Vilanova Manuel , Cerca Nuno , França Angela 

TITLE=mazEF Homologue Has a Minor Role in Staphylococcus epidermidis 1457 Virulence Potential

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=11

YEAR=2022

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2021.803134

DOI=10.3389/fcimb.2021.803134

ISSN=2235-2988

ABSTRACT=<p><italic>Staphylococcus epidermidis</italic> biofilm cells are characterized by increased antimicrobial tolerance and improved ability to evade host immune system defenses. These features are, in part, due to the presence of viable but non-culturable (VBNC) cells. A previous study identified genes potentially involved in VBNC cells formation in <italic>S. epidermidis</italic> biofilms, among which <italic>SERP1682/1681</italic> raised special interest due to their putative role as a toxin–antitoxin system of the <italic>mazEF</italic> family. Herein, we constructed an <italic>S. epidermidis</italic> mutant lacking the <italic>mazEF</italic> genes homologues and determined their role in (i) VBNC state induction during biofilm formation, (ii) antimicrobial susceptibility, (iii) survival in human blood and plasma, and (iv) activation of immune cells. Our results revealed that <italic>mazEF</italic> homologue did not affect the proportion of VBNC cells in <italic>S. epidermidis</italic> 1457, refuting the previous hypothesis that <italic>mazEF</italic> homologue could be linked with the emergence of VBNC cells in <italic>S. epidermidis</italic> biofilms. Additionally, <italic>mazEF</italic> homologue did not seem to influence key virulence factors on this strain, since its deletion did not significantly affect the mutant biofilm formation capacity, antimicrobial tolerance or the response by immune cells. Surprisingly, our data suggest that <italic>mazEF</italic> does not behave as a toxin–antitoxin system in <italic>S. epidermidis</italic> strain 1457, since no decrease in the viability and culturability of bacteria was found when only the <italic>mazF</italic> toxin homologue was being expressed.</p>