Supplementary material for "Interplay Of Virulence Factors and Signaling Molecules: Albumin And Calcium-Mediated Biofilm Regulation In Bordetella bronchiseptia"

Abstract

Bordetella bronchiseptica, a respiratory pathogen capable of infecting various mammals, including humans, is associated with chronic infections, contrasting with the acute infections caused by B. pertussis. Both pathogens can form biofilm-like structures in vivo, providing tolerance against environmental stresses. Biofilm formation in B. bronchiseptica is regulated by the BvgAS two-component system, with intermediate concentrations of certain modulators inducing a phase favoring biofilm formation. Recent studies have highlighted the role of cyclic diguanylate monophosphate (c-di-GMP) in this process: elevated c-di-GMP levels stimulate biofilm formation, whereas phosphodiesterase (PDE) activation reduces biofilms. Respiratory secretions, which contain albumin and calcium at higher concentrations than standard growth media, promote an increase in the amount and localization of the adenylate cyclase toxin (AC), an important Bordetella virulence factor. Secreted AC present in the extracellular media or attached to the outer membrane inhibits biofilm formation. Based on these observations, we hypothesized that serum albumin and calcium inhibit biofilm formation and explored the involvement of c-di-GMP in this process. Our findings demonstrate that albumin and calcium inhibit B. bronchiseptica biofilm formation by two apparently independent mechanisms, formation, increasing with AC secretion playing a significant role, while the filamentous hemagglutinin adhesin (FHA) does not appear to be directly involved. Furthermore,and inducing c-di-GMP degradation. regulates biofilm formation in response to albumin and calcium. This study enhances our understanding of the complex mechanisms governing B. bronchiseptica biofilm formation and its modulation by host factors.