Swimming in the sea: chemotaxis by marine bacteria

Abstract

Like many organisms, bacteria regularly inhabit environments characterised by spatiotemporal heterogeneity in the availability of resources required for growth and energy generation, meaning they must either tune their metabolism to prevailing conditions or have the capacity to migrate to favourable microenvironments1. To achieve the latter, bacteria measure their resource landscape and suitably direct their locomotion using a behaviour called chemotaxis, which is the ability to guide movement up or down chemical gradients. The capacity to perform chemotaxis is widespread across the bacterial domain, although most of our understanding of this phenotype is derived from enteric bacteria2,3. In the ocean, marine bacteria are often motile4, and in fact capable of much higher swimming speeds5 and chemotactic precision6 than these enteric models for chemotaxis2. Here we discuss the underlying motives and purposes for bacterial chemotaxis in the ocean, by noting that marine bacteria experience a surprisingly heterogeneous chemical seascape7,8, whereby chemotaxis can provide substantial fitness advantages and even influence large-scale processes including marine ecosystem productivity, biogeochemical cycling and disease.