A new biofilm-associated colicin with increased efficiency against biofilm bacteria

Abstract

Formation of bacterial biofilm communities leads to profound physiological modifications and increased physical and metabolic exchanges between bacteria. It was previously shown that bioactive molecules produced within the biofilm environment contribute to bacterial interactions. Here we describe new pore-forming colicin R, specifically produced in biofilms formed by the natural isolate Escherichia coli ROAR029 but that cannot be detected under planktonic culture conditions. We demonstrate that an increased SOS stress response within mature biofilms induces SOSdependent colicin R expression. We provide evidence that colicin R displays increased activity against E. coli strains that have a reduced lipopolysaccharide length, such as the pathogenic enteroaggregative E. coli LF82 clinical isolate, therefore pointing to lipopolysaccharide size as an important determinant for resistance to colicins. We show that colicin R toxicity toward E. coli LF82 is increased under biofilm conditions compared with planktonic susceptibility and that release of colicin R confers a strong competitive advantage in mixed biofilms by rapidly outcompeting sensitive neighboring bacteria. This work identifies the first biofilm-associated colicin that preferentially targets biofilm bacteria. Furthermore, it indicates that the study of antagonistic molecules produced in biofilm and multispecies contexts could reveal unsuspected, ecologically relevant bacterial interactions influencing population dynamics in natural environments.

Interrupting Biosynthesis of O Antigen or the Lipopolysaccharide Core Produces Morphological Defects in Escherichia coli by Sequestering Undecaprenyl Phosphate

“…One complicating factor was that commonly used derivatives of E. coli K-12 (e.g., MG1655) normally do not produce O antigen because the rhamnosyl transferase gene (wbbL) is disrupted by an insertion element (wbbL::IS5) (37). Rendueles et al recently constructed a derivative of E. coli MG1655 in which the wild-type wbbL allele was reintroduced (MG1655 wbbL ϩ ) (31). We obtained this strain and confirmed that it produced the O16 antigen (Fig.…”

“…The parent strain for this study was MG1655 wbbL ϩ (31). Restoration of O-antigen production in MG1655 wbbL ϩ obscures the lipopolysaccharide (LPS) core oligosaccharide, preventing P1-mediated generalized transduction.…”

Microbial Surface Colonization and Biofilm Development in Marine Environments

“…Some surface-associated bacteria use contact-dependent growth inhibition (CDI) systems that constitute cognate toxin-immunity protein pairs for interbacterial competition (703,704). The CDI systems are mainly type V secretion systems, and the secreted toxins display RNase, DNase, or membrane pore-forming activities toward target cells of the same species, suggesting the involvement of these systems in competition between closely related bacterial strains (703,705,706).…”

Post-Segregational Killing, Altruistic Cell Death, and Other Toxin/Antitoxin Fallacies

“…Nebulous nomenclature. Historically, TA systems were deemed cytosolic (not secreted); hence, TA system toxins were considered primarily to affect the metabolism of the host that produced it rather than 20 as serving as a weapon against other cells, such as colicins (Rendueles, et al, 2014). With a better understanding of their biological function, growth diminution as opposed to cell death, TA systems would be more aptly named "growth inhibitors" and "silencers of growth inhibitors," rather than "toxins," which imply a poison used against competitors rather than an internal means to reduce metabolism.…”