Providencia stuartii form biofilms and floating communities of cells that display high resistance to environmental insults

Abstract

Biofilms are organized communities of bacterial cells that are responsible for the majority of human chronic bacterial infections. Providencia stuartii is a Gram-negative biofilm-forming bacterium involved in high incidence of urinary tract infections in catheterized patients. Yet, the structuration of these biofilms, and their resistance to environmental insults remain poorly understood. Here, we report on planktonic cell growth and biofilm formation by P. stuartii, in conditions that mimic its most common pathophysiological habitat in humans, i.e. the urinary tract. We observed that, in the planktonic state, P. stuartii forms floating communities of cells, prior to attachment to a surface and subsequent adoption of the biofilm phenotype. P. stuartii planktonic and biofilm cells are remarkably resistant to calcium, magnesium and to high concentrations of urea, and show the ability to grow over a wide range of pHs. Experiments conducted on a P. stuartii strain knocked-out for the Omp-Pst2 porin sheds light on the role it plays in the early stages of growth, as well as in the adaptation to high concentration of urea and to varying pH.

Porin self-association enables cell-to-cell contact in Providencia stuartii floating communities

“…The latter may attach and grow on indwelling catheters (3,9,10) and on uroepithelial cells (11). Recently, we reported the microscopic characterization of P. stuartii plankton and biofilms and the unexpected finding that this species forms floating communities of cells in solution before its deposition as a surfaceattached biofilm (12). Within floating communities, cells are in apparent contact and presumably stick to one another via proteinprotein interactions (12).…”

“…Recently, we reported the microscopic characterization of P. stuartii plankton and biofilms and the unexpected finding that this species forms floating communities of cells in solution before its deposition as a surfaceattached biofilm (12). Within floating communities, cells are in apparent contact and presumably stick to one another via proteinprotein interactions (12). Inasmuch as the general diffusion porins are the most abundant proteins in the outer membrane (OM) of gram-negative bacteria, with a major porin often accounting for up to 70% of the OM protein content (up to 10 5 copies per cell) (13), we set out to verify whether P. stuartii porins could partake in the formation of floating communities.…”

“…The uptake of β-lactams (cephalosporins and carbapenems, in particular), quinolones, and fluoroquinolones is mainly due to their passive diffu-sion through Omp-Pst1 (6,7). Omp-Pst1 is essential to P. stuartii survival, while Omp-Pst2 promotes rapid growth, possibly through regulation of the cationic content of the periplasm (12).…”

Les porines : un rôle vital et un lien social au sein du biofilm de Providencia stuartii

“…Le biofilm de Providencia stuartii, une communauté soudée grâce aux porines Lors de précédents travaux, nous avons démontré que P. stuartii n'existe pas, à proprement parler, sous la forme planctonique puisque même en solution, ces bactéries s'assemblent en communautés flottantes [3]. Celles-ci se caractérisent par un contact membranaire étroit entre bactéries adjacentes et représentent ainsi, chez P. stuartii, une étape de socialisation nécessaire et préliminaire à celle d'adhérence à la surface en vue de former un biofilm canonique (Figure 1).…”

“…P. stuartii exprime deux porines au niveau de sa membrane externe, Omp-Pst1 et Omp-Pst2. Présentant une légère sélectivité pour les anions, Omp-Pst1 est une porine vitale pour la bactérie puisque la 3 Les brins β ont une torsion intrinsèque et quand huit à trente-six de ces brins β sont assemblés, ils peuvent former une structure en tonneau (β barrel). délétion du gène codant pour Omp-Pst1 (protéine non produite) est létale.…”