Sex hormones as a factor influencing microbial community of fish.

• Applicant: Dr.-Ing. Paulina Cholewinska
• Subject Area: Veterinary Medical Science
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 550698817

Increasing number of pollutant classes are being introduced to aquatic ecosystem compartments due to anthropogenic activities, including plastic particles, heavy metals, halogens or hormones, and the list of potential threats is continuously updated. Sex hormones, are among the most difficult organic substances to remove from sewage and the concentrations observed downstream of sewage treatment plant outflows are one of the highest that are observed in the aquatic environment. In the water environment we can observe differences in level of sex hormones that correlate to the surrounding environment. One of the main factors determining the degree of risk resulting from the presence of hormones in the environment is their half-life - from 12 h and up to 180 days in the case of water reservoirs without a stabilized population of microorganisms and with adequate physico-chemical conditions. Recent research efforts have focused on the influence of hormones on mammalian (including human) physiology and toxicology, and only a handful of studies have considered the interplay with microbial communities in affected organisms, and to my best knowledge, there are no published studies about role of environmental steroid endocrine disruptors on gut microbiomes in fishes. The main problem is that confounding factors can interfere with determination of the effect of the sex hormones on microbial communities in digestive tract. There is limited knowledge about roles of sex of the fish, age or diet, as well as individual genetic diversity, as determination factors of the microbiome communities. However, we at least are aware that each of the mentioned fundamental differences may affect the microbiome. In this study I will focus on develop and test utility of the novel fish model K. marmoratus for use in gut microbiome research, establish a baseline of microbiome composition in different time points under the consistent diet and laboratory conditions, and determine degree of statistical variations in the microbiome in individual fish specimens with identical/similar genetic background. However most important part will be expose Mangrove killifish to environmentally relevant concentrations of sex hormones in controlled environment and determine differences in microbiome composition over time in different control and experimental groups using novel technics.

• DFG Programme: WBP Position