Bordetella bronchiseptica BdcA regulates biofilm formation in a BrtA-dependent manner

FERNANDEZ, JULIETA; SISTI, FEDERICO; AMBROSIS, NICOLÁS MARTÍN

Paraná

Congreso; LIV Reunión Anual de SAIB; 2018

The genus Bordetella is composed of multiple species involved in airways tract infections. B. bronchiseptica is able to persist into their hosts during long periods of time and its biofilm formation ability is proposed to be involved in this process. In order to advance in the understanding of this host-pathogen interaction we analysed the contribution of the c-di-GMP regulated adhesin BrtA in physiologically relevant culture conditions. Hewllet and co-workers have recently shown that physiological concentrations of albumin and calcium (BSACa) elicit a massive increase in the RTX-family protein Adenylate Cyclase (AC) secretion. Like AC, the BrtA adhesin is a RTX-family protein so we hypothesised that BSACa could also have an effect on BrtA secretion. Our western blot results showed that BSACa also increased BrtA secretion. We also studied BrtA mediated biofilm formation in the presence of BSACa using multiple approaches. We used microtiter dishes, glasses and plastic tubes and analyzed the results using CV staining and Scanning Electron Microscopy. We observed a significantly reduction in biofilm formation in the ΔbrtA strain, while ΔlapG strain showed a significantly enhanced biofilm formation compared with wild type strain. To get a deeper understanding on the role of c-di-GMP in this process we performed biofilm formation assays with deletion mutants in two putative diguanylate cyclases involved in BrtA localization. Using biofilms and dot blots techniques we conclude that BdcA but not BdcG is involved in BrtA-dependent biofilm formation on these physiological conditions.