Distinct niche partitioning of marine and freshwater microbes during colonisation

Bacteria are ubiquitous on the Earth, and many use chemotaxis to colonise favourable microenvironments. The colonisation process is continuous, where animals, plants, protists, viruses and chemical and physical factors frequently remove bacteria from wide volume ranges. Colonisation processes are poorly understood in natural communities. Here, we investigated niche partitioning during colonisation in aquatic microbial communities using bands of bacterial chemotaxis in petri dishes from mixed-species communities. The community partitioned into loiterers, primary and secondary colonisers, each having distinct abundances and taxonomy. Within marine samples, Shewanella dominated the primary colonisers, whilst Enterobacteriaceae dominated this group within the freshwater samples. Whether the success of these specific groups translates to what occurs within natural communities is uncertain, but here we show these taxa have the capacity to colonise new, unexplored environments. A strong negative association existed between the primary colonisers and viral abundance, suggesting that successful colonisers simultaneously move toward areas of heightened resources, which correlated with lower virus-like particles. Here, we show that microbial communities constantly sort themselves into distinct taxonomic groups as they move into new environments. This sorting during colonisation may be fundamental to microbial ecology, industry, technology, and disease development by setting the initial conditions that determine the winners as a community develops.