Kin Recognition Systems and Their Role in Multicellular Behaviors

Interactions between individuals are at the foundation of every community. Furthermore, multicellular behaviors can emerge when individuals come together. Microbes—bacteria, fungi, archaea, and parasites—can engage in multicellular behaviors, which help with population dispersal, infections, and protection from environmental threats. A critical interaction in collectives is determining whether the interacting neighbor is a sibling (kin) or a nonsibling (nonkin). Multiple (molecular) ways exist to achieve kin recognition and discrimination, especially when fitness is essential. This review considers four bacterial and eukaryotic microorganisms that engage in collective migration and where recognition is known or implied as part of their emergent behavior. This comparative analysis considers shared themes about recognition behaviors among these social microbes, as well as open questions. As more is learned about why kin recognition occurs in different species, a greater understanding will emerge about its evolutionary history and the potential for exogenous control of microbial social groups.