Exploring the dynamics of a synthetic riverine bacterial community

The dynamics of a community of four 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-culture and quadriculture. Two interaction networks were constructed that summarise the impact of the strains on the growth rate of each other 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. is the fastest-growing strain and dominates the co-cultures. In general, we saw a correlation between growth rate and carrying capacity in this system. Moreover, growth rate in monoculture was predictive of carrying capacity in co-culture. This study increases our knowledge of interactions among riverine bacteria, which paves the way towards a better understanding of their response to pollution.