Bacterial communities are often well adapted and stable in a particular environment, be it a human mouth or a lake. Humans are changing environments at an increasing rate, not more so than in cities and their urbanizing surroundings. In a study published today in the journal Total Environmental Science, led by scientists from the Leibniz Institute for Freshwater Ecology and Inland Fisheries (IGB) and the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) as part of the Alliance of Leibniz research “Infections”, bacterial communities were examined in urban and waste water bodies in Berlin and in relation to lakes less influenced by anthropization in surrounding rural areas. The results reveal that urbanization introduces large amounts of nutrients, chemical pollutants and antimicrobials, and thus changes the composition of the microbiome by favoring groups of bacteria that contain human pathogenic bacteria, with as yet unknown consequences on the functioning. ecosystems and human and animal health.

Whether it’s an armpit, garden soil or water, almost every place on earth has its own natural bacterial community. By altering environments, humans also change the bacterial composition of these places by creating new conditions that favor certain groups of bacteria over others. In a new study, scientists from IGB and Leibniz-IZW along with colleagues from other members of the Leibniz Research Alliance tracked these changes in bacterial composition related to the urbanization process and demonstrated that bacterial communities in urban water bodies and waste water in Berlin are markedly different. those of rural lakes in the surrounding regions of the Länder of Brandenburg and Mecklenburg-Vorpommern. The urbanization process not only introduces human bacteria (“humanization”), but can also introduce excessive amounts of nutrients (“eutrophication”), chemical pollutants and antimicrobials such as antibiotics, which can radically promote specific bacteria over others and change the composition. of the microbiome with as yet unknown consequences on the functioning of ecosystems and human and animal health.

“We wanted to know if urban water exhibits signatures of urbanization that are predictive of the types of bacteria present in a given community within the city limits,” says IGB’s Professor Hans Peter Grossart, co-principal investigator of the study. The results demonstrate that multiple bacterial groups are enriched in urban waters, with the most extreme examples being found in the inlets and outlets of a sewage treatment plant, indicating a “humanization” of urban lake microbiomes.

“Surprisingly, the bacterial groups enriched in urban environments are those that often contain pathogenic species. This suggests that if a pathogen enters such an environment, it will find a very favorable environment in which to grow,” says Professor Alex Greenwood , head of the Leibniz-IZW Department of Wildlife Diseases and co-principal investigator of the study. This could potentially lead to disease outbreaks in such environments compared to rural water bodies, where such pathogen-friendly conditions were not usually found.

In the future, water hygiene may need to consider deurbanizing the microbiomes of city water sources to establish more natural aquatic ecosystems in the city. This will become increasingly difficult and important as climate change makes many urban areas drier and more nutrient rich, further altering the bacterial communities of urbanized water. This can have profound effects on human and animal health, as the risk of contamination with harmful microbes increases.

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Material provided by Leibniz Institute for Zoo and Wildlife Research (IZW). Note: Content may be edited for style and length.