A new component of the DNA damage response biofilm axis in <i>Acinetobacter baumannii</i> is a TetR-like DNA damage response regulator

Acinetobacter baumannii is an opportunistic pathogen that employs a variety of strategies to evade antibiotic treatment which include forming biofilms, which are protective bacterial multicellular communities. Previously, we demonstrated RecA, a key component of the DNA damage response (DDR), governs biofilms with RecA levels inversely correlated with biofilm formation, such that low RecA levels results in high biofilms. In this study, we identify another DDR regulator, EppR-a recently characterized TetR-family transcriptional repressor-as also playing a role in biofilms. We show that an eppR-deficient strain is unable to form biofilms due to reduced expression of genes encoding adhesive pili. This occurs because EppR represses recA expression. Furthermore, we detected in biofilms an EppR-RecA complex that might lower intracellular RecA levels. Our findings provide further insight into both RecA regulation and the link between the DDR and biofilms.