The Formation and Stability of a Microbial Community

New communities form regularly in nature, as many species rush to colonise a freshly formed island, pool, or microbiome, but it is unclear what rules govern the arrangement of these founders into a smaller, stable community, or whether the process is predictable. I simultaneously inoculated a master mix of bacterial colonisers into 45 identical environments, and allowed them to compete and evolve for around three months. By the end of the experiment, the species compositions of these communities had split into two broad groups, defined mostly by the mutual exclusivity of two Pseudomonas species, which may represent the ecological equivalence of the two species. Due to this functional similarity, I propose that community formation may be predictable at an ecological level, if not a taxonomic level. I also explored one of the communities formed in this experiment in further detail, investigating the maintenance of its diversity and stability. The community was fairly stable, as every species was able to persist even when it began at a much lower population size than its competitors, and no diversity was lost after 4 weeks of culture. I grew the species from this community in monoculture, as well as in every possible pair, triplet, and quartet, to fully assess the network of interactions, and found evidence for many significant higher-order interactions, which have been shown to have a stabilising effect in theoretical models