Exploring the dynamics of a synthetic riverine bacterial community

Abstract The dynamics of a community of four planktonic bacterial strains isolated from river water was followed in R2 broth for 72 h in batch experiments. 16S rRNA gene sequencing and flow cytometry analyses were combined to monitor the change in abundance of each individual strain in bi-cultures and quadriculture. Two interaction networks were constructed that summarise the impact of the strains on each other’s growth rate in exponential phase and carrying capacity in stationary phase. The networks agree on the absence of positive interactions, but also show differences, implying that ecological interactions can be specific to particular growth phases. Janthinobacterium sp. was the fastest-growing strain and dominated the co-cultures. However, its growth rate was negatively affected by the presence of other strains 10 to 100 times less abundant than Janthinobacterium sp. In general, we saw a positive correlation between growth rate and carrying capacity in this system. In addition, growth rate in monoculture was predictive of carrying capacity in co-culture.