Microbial invasion of a toxic medium is facilitated by a resident community but inhibited as the community co-evolves

Abstract

Predicting whether microbial invaders will colonize an environment is critical for managing natural and engineered ecosystems, and controlling infectious disease. Invaders often face competition by resident microbes. But how invasions play out in communities dominated by facilitative interactions is less clear. We previously showed that growth medium toxicity can promote facilitation between four bacterial species, as species that cannot grow alone rely on others to survive. Following the same logic, here we allowed other bacterial species to invade the four-species community and found that invaders could more easily colonize a toxic medium when the community was present. In a more benign environment instead, invasive species that could survive alone colonized more successfully when the residents were absent. Next, we asked whether early colonists could exclude future ones through a priority effect, by inoculating the invaders into the resident community only after its members had co-evolved for 44 weeks. Compared to the ancestral community, the co-evolved resident community was more competitive toward invaders and less affected by them. Our experiments show how communities may assemble by facilitating one another in harsh, sterile environments, but that arriving after community members have co-evolved can limit invasion success.

The evolution of reduced facilitation in a four-species bacterial community

“…Indeed, At evolving alone was the only condition where degradation improved over the course of the experiment and largely surpassed the degradation ability of the community, even though the community includes At . In follow-up experiments reported elsewhere we also found that new, non-resident species were more likely to invade the ancestral compared to the evolved community 44 , suggesting that the community members evolved to cover the available niche space. An alternative initial hypothesis was that positive interactions might increase, leading to the evolution of mutualism (H1 in Fig.…”

“…Over the 44 transfers (Fig. 5A), Ct and the two evolved communities reduced their degradation efficiency, such that at the end, they degraded less than their ancestral counterparts (%COD on day 7, isolates from transfer 1 vs. 44 Knowing that At was a member of the two evolved communities, we wondered why the degradation efficiency of the communities was worse than At evolved alone. Did the community members inhibit the degradation efficiency of At or did it not evolve improved degradation?…”

Convergence effect during spatiotemporal succession of lacustrine plastisphere: loss of priority effects and turnover of microbial species

“…changes in microbial communities colonizing the surface of microplastics are continuously exchanged with microorganisms in the surrounding water [ 13 , 40 ]. However, as the succession of microbial communities in the plastisphere progresses, resident taxa may occupy more ecological niches and monopolize resource availability in colonized environments, thereby reducing further microbial invasions [ 41 ].…”

The underground network: facilitation in soil bacteria

“…The relationship of facilitation to community invasion thus depends on a complex interplay between the resident community's existing niche partitions (Wei et al 2015), environmental conditions (Yang et al 2017) and species' specific or evolutionary effects (van der Putten et al 2007, Jousset et al 2013). The effect of facilitation on such emergent properties has remained a pressing unknown in facilitation research for the last two decades (Richardson et al 2000, Stachowicz and Byrnes 2006, Li et al 2018, Piccardi et al 2022).…”