Microbial interactions play a critical role in ecosystem stability.
However, the degree of competition and cooperation that are reflected in
the observed composition of microbial communities and their response to
alterations in nutrient availability has not been systematically
investigated. Thus, we utilized monocultures and pairwise co-cultures in
order to measure changes in the growth, niche and interactions among
sixteen cultured rhizosphere soil bacteria across different carbon types
and nutrient availabilities. Our analysis showed that interactions
differed among strain pairs and across carbon sources. We further found
that resource limitation resulted in ∼3% greater increases in microbial
inhibition and more negative interactions. In contrast, high nutrient
concentrations allowed for bacterial metabolic niche expansion, a
decrease in inhibition (79.69% of cases) and stronger facilitation.
Overall, our results show that the prevalence of cooperation is higher
in nutrient-rich conditions, thus revealing the critical role that
resource availability plays in shaping microbial interactions.