Biofilm formation and toxin production provide a fitness advantage in mixed colonies of environmental yeast isolates

Abstract

Microbes can engage in social interactions ranging from cooperation to warfare. Biofilms are structured, cooperative microbial communities. Like all cooperative communities, they are susceptible to invasion by selfish individuals who benefit without contributing. However, biofilms are pervasive and ancient, representing the first fossilized life. One hypothesis for the stability of biofilms is spatial structure: Segregated patches of related cooperative cells are able to outcompete unrelated cells. These dynamics have been explored computationally and in bacteria; however, their relevance to eukaryotic microbes remains an open question. The complexity of eukaryotic cell signaling and communication suggests the possibility of different social dynamics. Using the tractable model yeast, Saccharomyces cerevisiae, which can form biofilms, we investigate the interactions of environmental isolates with different social phenotypes. We find that biofilm strains spatially exclude nonbiofilm strains and that biofilm spatial structure confers a consistent and robust fitness advantage in direct competition. Furthermore, biofilms may protect against killer toxin, a warfare phenotype. During biofilm formation, cells are susceptible to toxin from nearby competitors; however, increased spatial use may provide an escape from toxin producers. Our results suggest that yeast biofilms represent a competitive strategy and that principles elucidated for the evolution and stability of bacterial biofilms may apply to more complex eukaryotes.

Filamentous Non-albicans Candida Species Adhere to Candida albicans and Benefit From Dual Biofilm Growth

“…We observed a lag in biofilm growth in Ca+Ct co-culture compared to Ca alone; however, surface coverage of the biofilm past 8.5 h ultimately exceeded what C. tropicalis was capable of producing alone, indicating a clear benefit for C. tropicalis . The potential advantages of rapidly establishing and participating in a mature biofilm are numerous, including protection from environmental stresses (Pemmaraju et al, 2016), antifungal agents (Chandra et al, 2001), and other competing microbiota (Deschaine et al, 2018). Conversely, mono-culture biofilms of C. tropicalis have also been shown to be more resistant to antifungal diffusion than C. albicans biofilms (Al-Fattani and Douglas, 2006), which could offer a benefit to C. albicans in Ca+Ct biofilms.…”

Variation at an adhesin locus suggests sociality in natural populations of the yeast Saccharomyces cerevisiae

“…In a growing, spatially structured community, individuals at the edge of the leading front have access to nutrients and space [58]; thus, production of substances that facilitate cell–cell adherence can be a competitive strategy [62,63]. Indeed, competitions between biofilm-forming and non-biofilm-forming yeast strains have shown a fitness benefit to biofilm production, with the biofilm-forming strains dominating the outer edge of the community [64]. We tested the effect of natural FLO11 alleles and found that certain alleles were competitively dominant in mats, suggesting that the natural variation we observed can have a profound effect on social phenotypes.…”

Characterization of Fitness Cost Caused by Tigecycline-Resistance Gene tet(X6) in Different Host Bacteria

“…By contrast, a decreased competitive ability was found in E. coli TOP10 (tet(X6)/pBAD) and S. Enteritidis ATCC13076 (tet(X6)/pBAD) when the L-arabinose concentration was above 0.1 mM (Figures 3A1, B1). Previous studies have reported that bacterial biofilm production is related to its survival status, thus, the ability of biofilm formation can also reflect bacteria fitness [26,27]. A crystal violet staining method was applied to evaluate the ability of biofilm formation in different host bacteria carrying the tet(X6) gene.…”