Microeukaryotic gut parasites in wastewater treatment plants: diversity, activity, and removal

Abstract

Background During wastewater treatment, the wastewater microbiome facilitates the degradation of organic matter, reduction of nutrients, and removal of gut parasites. While the latter function is essential to minimize public health risks, the range of parasites involved and how they are removed is still poorly understood. Results Using shotgun metagenomic (DNA) and metatranscriptomic (RNA) sequencing data from ten wastewater treatment plants in Switzerland, we were able to assess the entire wastewater microbiome, including the often neglected microeukaryotes (protists). In the latter group, we found a surprising richness and relative abundance of active parasites, particularly in the inflow. Using network analysis, we tracked these taxa across the various treatment compartments and linked their removal to trophic interactions. Conclusions Our results indicate that the combination of DNA and RNA data is essential for assessing the full spectrum of taxa present in wastewater. In particular, we shed light on an important but poorly understood function of wastewater treatment – parasite removal.

Active predation, phylogenetic diversity, and global prevalence of myxobacteria in wastewater treatment plants

“…These two strains were grown in minimal salt medium (MSM; Coolaber) containing 4 g l −1 99% 13 C 6 -glucose (Cambridge Isotope Laboratories, Inc.) as the sole carbon source. The same strains were cultivated in MSM medium with 12 C-glucose (Sigma Aldrich). Bacterial cells were transferred once with the same medium, harvested, washed, and resuspended in MSM.…”

“…The 13 C-labeled E. coli and P. putida cells were added to 10 ml of activated sludge to achieve a targeted concentration of 2 × 10 8 cells ml −1 in glass bottles closed with screw cap and rubber stopper. In parallel, 12 C-E. coli and P. putida cells were added to the 12 C-microcosms and a control group without cell amendment was set up. Bottles were destructively sampled with duplicate microcosms after 16 h, one day, two days, four days, and eight days of incubation, resulting in a total of 50 glass bottles.…”

“…To identify the ASVs and microbial genera that incorporated the 13 C-labeled E. coli or P. putida biomass, we employed an "enrichment factor" (EF) to infer the enrichment of the corresponding sequences in 13 C-heavy fractions as previously applied [40,48] and calculated as follows: EF ¼ 13c Heavy 13c Light À 12c Heavy 12c Light (1) where Heavy and Light are the taxon-specific relative sequence abundance in the selected heavy and light fractions of a gradient, and 13 C and 12 C in this formula refer to the treatments with 13 C-labeled and unlabeled cells. EFs were calculated for all the prokaryotic and eukaryotic genera with >1% read abundance, and ASVs with >0.1% read abundance in heavy rRNA fractions of at least one treatment at a sampling time point.…”

“…However, intrabacterial predation has been largely neglected in prior studies on wastewater treatment microbiota, although predatory bacteria are ubiquitous in environment and particularly regarded as "living antibiotics" due to their capability to kill a range of human and plant pathogens [8][9][10]. Compared with the well-studied protozoa [11,12] and bacteriophages [13,14], predatory bacteria, especially their grazing behaviors on the beneficial (e.g., carbon and nitrogen-removing) or detrimental (e.g., antibiotic resistant and pathogenic) bacteria in WWTPs, remain largely unexplored, which impedes a comprehensive understanding of food web interactions therein and development of specific engineering solutions, based on such intricate ecological interactions, to prevent system performance deterioration, solve long-standing operational problems (e.g., bulking and foaming), or tackle sanitation challenges (e.g., COVID-19 and antimicrobial resistance).…”

Resistance of Blastocystis to chlorine and hydrogen peroxide

“…Several factors have been linked with increased occurrence of Blastocystis with waterborne transmission featuring prominently (Anuar et al 2013;Deng et al 2020;Salazar-Sanchez et al 2021). Blastocystis has been detected in drinking water (Leelayoova et al 2008), tap water (Eroglu and Koltas 2010;Jinatham et al 2022), rainwater tanks (Waters et al 2019;Jinatham et al 2021), bodies of freshwater (Khalifa et al 2014), drinking water treatment facilities (Richard et al 2016;Freudenthal et al 2022), and wastewater worldwide.…”