Impact of a widespread herbicide on infectious disease dynamics in phytoplankton and fungi host-parasite interactions

• Applicant: Dr. Erika Berenice Martínez Ruiz
• Subject Area: Microbial Ecology and Applied Microbiology
• Term: from 2022 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 471387895

The presence of pollutants from anthropogenic sources in water bodies threatens water quality and the whole aquatic ecosystems. Herbicides are frequently found in water systems due to their continuous use in agriculture worldwide. Metolachlor (MET) is the sixth most globally used herbicide. MET negatively affects non-target aquatic organisms, including phytoplankton. Phytoplanktonic organisms, like cyanobacteria, are primary producers and thus key players in aquatic environments. Eutrophication and other anthropogenic pressures promote cyanobacteria growth within phytoplanktonic communities. Uncontrolled cyanobacterial growth in water bodies leads to the formation of cyanobacterial blooms. Cyanobacterial blooms negatively impact the environment, the economy, and the health of humans and animals. Fungal parasitism regulates cyanobacterial growth in aquatic environments. Fungal infections occur worldwide and are relevant for the dynamics, trophic interactions, and evolution of phytoplankton. The most important parasites of phytoplankton are chytrids. Information regarding the impact of anthropogenic pollutants on chytrid parasites and phytoplanktonic hosts is limited. Chytrid parasites and phytoplanktonic hosts within the aquatic ecosystem are involved in a complex network of interactions with other organisms such as heterotrophic bacteria. Co-existing heterotrophic bacteria profit from chytrid infection in phytoplanktonic hosts due to the release of dissolved organic carbon upon phytoplankton lysis. However, it is unclear how this plays out in the sustained presence of pollutants. Chytrid fungi and their hosts (e.g. cyanobacteria) are ecologically relevant. Therefore, it is pivotal to understand the impact of widespread anthropogenic pollutants, like MET, on their infection dynamic. This proposal aims to investigate how a widespread herbicide impacts the infection dynamic of a chytrid parasite and its toxigenic cyanobacterial host. To accomplish this goal, this proposal has three objectives. First, I will determine to which extent the exposure to MET promotes the infection of toxigenic cyanobacteria by chytrid parasites. Second, I will evaluate the transcriptional and metabolic response of cyanobacteria and chytrids in their interaction while exposed to MET to gain understanding of its toxicity mechanism. And third, I will test whether sustained exposure to MET can act as a selective pressure promoting growth of MET-degrading bacterial groups. The successful completion of this project would expand our understanding of the anthropogenic impact on phytoplankton and disease dynamics. Furthermore, it will deepen our knowledge on how pollutants affect ecological interactions between species at the multi-organisms level, such as host-parasite interactions.

• DFG Programme: WBP Position