Evolution of Hitchhiking Interactions in Microbes

Abstract

Abstract Many microbes migrate from unfavourable environments to more favourable ones. They will, for example, seek out nutrients, prey, and hosts or avoid toxins, heat or salinity. However, motility also incurs metabolic costs, and accordingly, for many microbes, it is not cost‐effective to be motile. Interestingly, many nonmotile microbes have been observed to utilize their motile neighbours to ‘hitchhike’ to more favourable environments. Microbial hitchhiking seems quite widespread and has potential impacts on ecological community function and formation. The ecology and evolution of hitchhiking appears to be varied, with interactions ranging from parasitic to mutualistic. Key Concepts Cell motility is crucial for many key functions in microbial populations but comes with metabolic costs and not all microbes possess the machinery to be motile. Four separate mechanisms of hitchhiking in microbes have been identified thus far. These are mechanical pushing by motile cells, direct attachment to cell bodies, direct attachment to bacterial flagella and internal transport by cells. Microbial hitchhiking can be parasitic, commensal, or mutualistic. Microbial hitchhiking can also be mutually beneficial, where both motile and nonmotile counterparts benefit, for example in combining functions such as antibiotic resistance. Microbial hitchhiking can have important ecological implications, including influencing the composition and function of microbial communities and the spread of pathogens. Many motile counterparts in hitchhiking interactions use chemotaxis to move towards more favourable environments.