Predatory and parasitic microeukaryotes in wastewater treatment plants - diversity & function

Microeukaryotes, in particular protists, have been relatively overlooked in wastewater treatment studies due to methodological biases favoring prokaryotes. Applying metatranscriptomics has enabled us to address these biases, and in this presentation, I will provide a summary of four recent studies examining the entire wastewater microbiome, encompassing prokaryotes, fungi, protists, and microscopic metazoa (Heck et al. 2023, Freudenthal et al. 2022, Pohl et al. 2021, Solbach et al. 2021).

Our primary focus has been on exploring biotic interactions within wastewater, leading to several noteworthy findings: 1. Microeukaryotic predators shape the prokaryotic community composition and thus are integral for well-performed wastewater treatment. 2. Gut parasites among microeukaryotes exhibit heightened activity in wastewater but undergo effective reduction during denitrification, likely influenced by microbial predation. 3. The so-far overlooked, but most abundant wastewater protist worldwide, Rhogostoma minus, hosts Legionellales and potentially functions as a vector for Legionnaire's disease in humans. These findings underscore the significance of investigating microbial eukaryotes in wastewater, now made feasible with advanced tools.