Can a microbial community become an evolutionary individual?

Microbial communities provide crucial services for human well-being, driving an interest in designing and controlling them towards optimised or novel functions. Unfortunately, promising strategies such as community breeding - sometimes referred to as 'directed evolution' or 'artificial community selection' - have shown limited success. A key issue is that microbial communities do not reliably exhibit heritable variation, limiting their capacity for adaptive evolution. In other words, microbial communities are not evolutionary individuals. Here, we provide an overview of the literature on evolutionary transitions in individuality and, with insights from paradigmatic organisms, build a multidimensional space in which the individuality of a multispecies community is characterised by three ecological traits: positive interactions, functional integration, and entrenchment. We then place microbial communities within this individuality space, explore how they can be directed toward increased individuality, and discuss how this perspective can help improve our approach to community breeding.