Microbial analysis is challenged by immigration

High throughput characterisation of microbial communities is widely used as a source of information to develop strategies for improved biological processes in humans, animals and engineered systems. However, the introduction of organisms that do not contribute or grow in the system can ruin conclusions derived from the composition. In this study we sequenced samples from digesters and their influent streams to evaluate which organisms were truly growing and which were probably just continuously fed into the system.