Even in their own environment, specialist microbes are dominated by generalists

Specialized microorganisms that are found in only one type of environment turn out to occur there in relatively low but stable numbers. Microorganisms that live in many different types of environments, on the other hand, are able to rapidly increase in numbers when conditions are favourable. Researchers from Utrecht University and the Friedrich-Schiller-Universität Jena conclude this based on a new method to distinguish generalist and specialist microbes, which they applied to a large, global dataset. The results of the study were published yesterday in the journal Nature Ecology & Evolution. Bastiaan von Meijenfeldt, first author of the paper and former PhD candidate at Utrecht University, explains what made this study possible. Von Meijenfeldt: "It has actually only recently become possible to take a sample from the environment, for example from the sea, the soil or the intestines of a human being, and then use the DNA in that sample to determine which microorganisms such as bacteria and archaea are present in it. In recent years, a lot of researchers around the world have done so, and their datasets have often ended up online. We decided to collect this online data. Doing so, we were able to combine data from more than 22 thousand samples taken from all kinds of different environments, such as coastal zones, plants and human faeces. Then we used that data to investigate, for the first time on such large scale, which microbes are generalists and specialists." Microbiomes. Within ecology, organisms are called generalists when they occur in many different types of environment. But how do you define these environments?