The Role of Biofilm-Derived Compounds in Microbial and Protozoan Interactions

Biofilms are more than just structural microbial communities. They are dynamic chemical ecosystems that synthesize a range of extracellular compounds involved in functions that extend beyond biofilm architecture. From quorum-sensing molecules like acyl-homoserine lactones (AHLs) to short-chain fatty acids (SCFAs), phenazines, indoles, and reactive sulfur species (RSS), biofilm-derived metabolites can impact the physiology and behavior of microorganisms living in the same ecosystem, including other bacteria and protozoa. It has recently been demonstrated that such molecules may also modulate competition between microbes, promote cooperation, and impact motility, differentiation, or virulence of free-living and parasitic protozoa. This review aims to discuss biofilm compounds that mediate interspecies or interkingdom interactions and their involvement in regulating gut and environmental microbiomes functions, and host-pathogen relationships with special emphasis on protozoan activity and the infection outcome. This review will also address how this chemical dialog can be explored to identify new therapeutic interventions against microbial infections and parasitic diseases.