Bacterial communities are frequently well adapted and stable in a specific environment, such as a human mouth or a lake. Humans are altering their environments at an increasing rate, none more so than in cities and their surrounding areas during the urbanization process. In a study 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 Leibniz Research Alliance “Infections,” bacterial communities in urban water bodies and wastewater in Berlin were compared to less anthropogenically influenced lakes from surrounding rural regions.
The findings show that urbanization introduces large amounts of nutrients, chemical pollutants, and antimicrobial products, changing the makeup of the microbiome by favoring groups of bacteria that contain human pathogenic bacteria, with unknown consequences for ecosystem functioning and human and animal health.
We wanted to know if there are urbanization signatures in water that predict the types of bacteria present in a given community within city limits. The findings show that multiple bacterial groups are enriched in urban waters, with the most extreme examples found in the inflows and outflows of a wastewater treatment plant, indicating that urban lake microbiomes are being “humanized.”
Prof Hans Peter Grossart
Whether it’s an armpit, garden soil, or water, almost every place on Earth has its own natural bacterial community. Humans change the bacterial composition of environments by creating new conditions that favor some groups of bacteria over others. In a new study, scientists from IGB and Leibniz-IZW, along with colleagues from other Leibniz Research Alliance members, tracked these changes in bacterial composition linked to the process of urbanization and demonstrated that bacterial communities in urban waterbodies and wastewater in Berlin are distinctly different from those in rural lakes in surrounding regions in the federal states of Brandenburg and Mecklenburg-Vorpommern.
The process of urbanization not only introduces human bacteria (“humanisation”), but also excessive amounts of nutrients (“eutrophication”), chemical pollutants, and antimicrobial products such as antibiotics, which can drastically favor specific bacteria over others and change the makeup of the microbiome, with yet unknown consequences for ecosystem functioning and human and animal health.
“We wanted to know if there are urbanization signatures in water that predict the types of bacteria present in a given community within city limits,” says Prof Hans Peter Grossart of the IGB, co-principal investigator of the study. The findings show that multiple bacterial groups are enriched in urban waters, with the most extreme examples found in the inflows and outflows of a wastewater treatment plant, indicating that urban lake microbiomes are being “humanized.”
“Surprisingly, pathogenic bacteria are frequently found in enriched bacterial groups in urban environments. This implies that if a pathogen enters such an environment, it will find a very supportive environment to grow in” Prof Alex Greenwood, co-principal investigator of the study and head of the Leibniz-IZW Department of Wildlife Diseases, says This could lead to outbreaks in such environments, as opposed to rural water bodies, where such favourable conditions for pathogens were not generally found.
Water hygiene may need to consider de-urbanizing the microbiomes of city water sources in the future to establish more natural water ecosystems within the city. This will become more difficult and important as climate change causes many urban areas to become drier and more nutrient-rich, altering the bacterial communities of urbanized water. As the risk of contamination with harmful microbes increases, this could have serious consequences for human and animal health.
Although urbanization has a significant impact on headwater stream chemistry and hydrology, little is known about how these conditions affect bacterial community composition. We predicted that urbanization would have an effect on bacterial community composition, but that at the watershed scale, as measured by impervious cover, stream water column bacterial communities would be most strongly linked to urbanization, whereas sediment bacterial communities would correlate with environmental conditions at the stream reach scale.
