The largest freshwater bacterium, Achromatium oxaliferum, is highly flexible in its requirements, as researchers led by the Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB) have now discovered: It lives in places that differ extremely in environmental conditions such as hot springs and ice water. The bacterial strains from the different ecosystems do not differ in their gene content, but rather choose what to express. The adaptation is probably achieved by a process which is unique to these bacteria: only relevant genes are enriched in the genomes and transcribed, while others are archived in cell compartments.