Screening of Escherichia coli Species Biodiversity Reveals New Biofilm-Associated Antiadhesion Polysaccharides

Abstract

Bacterial biofilms often form multispecies communities in which complex but ill-understood competition and cooperation interactions occur. In light of the profound physiological modifications associated with this lifestyle, we hypothesized that the biofilm environment might represent an untapped source of natural bioactive molecules interfering with bacterial adhesion or biofilm formation. We produced cell-free solutions extracted from in vitro mature biofilms formed by 122 natural Escherichia coli isolates, and we screened these biofilm extracts for antiadhesion molecules active on a panel of Gram-positive and Gram-negative bacteria. Using this approach, we showed that 20% of the tested biofilm extracts contained molecules that antagonize bacterial growth or adhesion. We characterized a compound, produced by a commensal animal E. coli strain, for which activity is detected only in biofilm extract. Biochemical and genetic analyses showed that this compound corresponds to a new type of released high-molecular-weight polysaccharide whose biofilm-associated production is regulated by the RfaH protein. We demonstrated that the antiadhesion activity of this polysaccharide was restricted to Gram-positive bacteria and that its production reduced susceptibility to invasion and provided rapid exclusion of Staphylococcus aureus from mixed E. coli and S. aureus biofilms. Our results therefore demonstrate that biofilms contain molecules that contribute to the dynamics of mixed bacterial communities and that are not or only poorly detected in unconcentrated planktonic supernatants. Systematic identification of these compounds could lead to strategies that limit pathogen surface colonization and reduce the burden associated with the development of bacterial biofilms on medical devices.

Potential Novel Therapeutic Strategies in Cystic Fibrosis: Antimicrobial and Anti-Biofilm Activity of Natural and Designed α-Helical Peptides Against Staphylococcus aureus, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia

“…Inhibiting biofilm formation of a wide range of bacteria without affecting their growth represents a special feature of the polysaccharide described in this report. This characteristic has already been described for other polysaccharides in a few very recent articles [40][41][42]. Further research on such surface-active compounds might help developing new classes of anti-biofilm molecules with broad spectrum activity and more in general will allow to explore new functions of bacterial polysaccharides in the environment.…”

“…In addition, pre-coating the wells of the polystyrene microtiter plate with the compound also effectively inhibits biofilm formation. To our knowledge, coating with the polysaccharide from sponge-associated bacteria for inhibition of biofilm formation has been reported for the first time here, although there are some reports on the use of pre-coating surfaces with different surfactants and enzymes [38][39][40][41].…”

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

“…Consistently, biofilm communities were shown to release molecules that affect bacterial access to space and resources. Examples of such compounds range from metabolites and amino acids (Valle et al, 2008;Kolodkin-Gal et al, 2010 to anti-adhesion molecules (Bendaoud et al, 2011;Rendueles et al, 2011Rendueles et al, , 2013 and bacteriocins (Yan et al, 2003;Kreth et al, 2004).…”

Biofilm-Related Infections: Bridging the Gap between Clinical Management and Fundamental Aspects of Recalcitrance toward Antibiotics

“…Such molecules have therefore been studied as a possible surface modification in order to prevent bacterial adhesion. For instance, group 2 capsule and Ec300p, two hydrophilic high-molecular-weight polysaccharides produced by different E. coli strains, have been shown to prevent biofilm formation of Gram-positive and/or Gram-negative pathogens (265,266). Other molecules have been tested, including surfactin, rhamnolipids, and other molecules produced by lactobacilli and Streptococcus thermophilus, although these have not been identified clearly (see the reviews in references 263 and 267).…”