Selection on plastic adherence leads to hyper-multicellular strains and incidental virulence in the budding yeast

Abstract

Many disease-causing microbes are not obligate pathogens; rather, they are environmental microbes taking advantage of an ecological opportunity. The existence of microbes that are not normally pathogenic, yet are well-suited to host exploitation, is an evolutionary paradox. One hypothesis posits that selection in the environment may favor traits that incidentally lead to pathogenicity and virulence, or serve as pre-adaptations for survival in a host. An example of such a trait is surface adherence. To experimentally test the idea of »accidental virulence», replicate populations of the yeast, Saccharomyces cerevisiae, which can be an opportunistic pathogen, were evolved to attach to a plastic bead for hundreds of generations. Along with plastic adherence, two multicellular phenotypes— biofilm formation and flor formation— increased; another phenotype, pseudohyphal growth, responded to the nutrient limitation. Thus, experimental selection led to the evolution of highly-adherent, hyper-multicellular strains. Wax moth larvae injected with evolved hyper-multicellular strains were significantly more likely to die than those injected with evolved non-multicellular strains. Hence, selection on plastic adherence incidentally led to the evolution of enhanced multicellularity and increased virulence. Our results support the idea that selection in the environment for a trait unrelated to virulence can inadvertently generate opportunistic, »accidental» pathogens.

Isolation of human pathogenic Candida species colonising plastic wastes: environmental screening for drug resistance, thermotolerance, and virulence of ‘WHO Priority Fungal Pathogens’

“…Whether bio lm formation on environmental plastic surfaces increases the expression of adhesion factors of environmental isolates of Candida and whether this in uences subsequent mechanisms of pathogenicity is unknown. Understanding colonisation of plastic surfaces, and the in uence of the plastisphere for altering virulence and drug resistance pro les of fungal pathogens is urgently needed to more fully quantify the potential human health risks of plastic pollution (Ormsby et al, 2023;Ekdahl et al, 2023).…”

“…Most Candida species are non-pathogenic environmental microbes, persisting in sources such as food, water or plants (Angebault et al 2013;Miranda et al 2009). However, several species are potentially pathogenic, taking advantage of the opportunity to colonise humans and cause disease (Ekdahl et al, 2023). Candida can survive the transition through wastewater treatment plants (WWTPs) (Assress et (Wallbank et al, 2022).…”