Investigating the invisible life in our environment

Microorganisms make up more than a third of the Earth's biomass. They are found in water, on land and even in our bodies, recycling nutrients, influencing the planet's climate or causing diseases. Still, we know surprisingly little about the smallest beings that colonise Earth. A new computational method to analyse environmental DNA samples now sheds light on the microbial composition of different habitats, from soil to water. The study reveals that microbes evolve faster in some environments than in others and that they rather rarely change their habitat preferences over time. Studying microorganisms has proven very difficult because most naturally occurring types do not grow in the lab. The rapidly growing field of environmental DNA sequencing now helps to overcome this problem. Instead of analysing the genome of a specific organism, scientists sequence all the DNA they find in environmental samples, ranging from seawater to soil. They collect vast amounts of sequence fragments, which contain genetic information of thousands of species forming communities that colonise a certain habitat.