CNRS scientists and international collaborators have shown that Parisian street gutters are oases of microscopic life, home to microalgae, fungi, sponges and mollusks. Grouped into communities, these microorganisms may help clean rainwater and urban waste by decomposing solid debris and pollutants such as exhaust fumes and engine oil. A deeper understanding of the role and composition of these communities could help elucidate the services rendered by gutter ecosystems. Published in the ISME Journal on October 13, 2017, the researchers’ findings are the first to reveal the unsuspected biodiversity of microscopic life in Paris city streets.