AUTHOR=Roussin Morgane , Rabarioelina Sedera , Cluzeau Laurence , Cayron Julien , Lesterlin Christian , Salcedo Suzana P. , Bigot Sarah 

TITLE=Identification of a Contact-Dependent Growth Inhibition (CDI) System That Reduces Biofilm Formation and Host Cell Adhesion of Acinetobacter baumannii DSM30011 Strain

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.02450

DOI=10.3389/fmicb.2019.02450

ISSN=1664-302X

ABSTRACT=<p><italic>Acinetobacter baumannii</italic> is a multidrug-resistant nosocomial opportunistic pathogen that is becoming a major health threat worldwide. In this study, we have focused on the <italic>A. baumannii</italic> DSM30011 strain, an environmental isolate that retains many virulence-associated traits. We found that its genome contains two loci encoding for contact-dependent growth inhibition (CDI) systems. These systems serve to kill or inhibit the growth of non-sibling bacteria by delivering toxins into the cytoplasm of target cells, thereby conferring the host strain a significant competitive advantage. We show that one of the two toxins functions as a DNA-damaging enzyme, capable of inducing DNA double-stranded breaks to the chromosome of <italic>Escherichia coli</italic> strain. The second toxin has unknown catalytic activity but stops the growth of <italic>E. coli</italic> without bactericidal effect. In our conditions, only one of the CDI systems was highly expressed in the <italic>A. baumannii</italic> DSM30011 strain and was found to mediate interbacterial competition. Surprisingly, the absence of this CDI system promotes adhesion of <italic>A. baumannii</italic> DSM30011 to both abiotic and biotic surfaces, a phenotype that differs from previously described CDI systems. Our results suggest that a specific regulation mediated by this <italic>A. baumannii</italic> DSM30011 CDI system may result in changes in bacterial physiology that repress host cell adhesion and biofilm formation.</p>