Shifts and rebound in microbial community function following repeated introduction of a novel species

Natural microbial communities continually encounter novel species that may
successfully establish or simply be transient, yet both outcomes can alter
the resident community composition and function. Preserving natural
microbial communities and innovating synthetic ones requires insight on
the immediate and long-term impact of species introductions on both
composition and function. For instance, it remains unclear whether there
are gradual and long-term impacts from repeated introductions where the
introduced species fails to establish – so-called failed invaders. To
investigate the persistent impacts by failed invaders, we present an
experimental test of community stability over multiple generations against
repeated novel species introduction. We propagated a natural microbial
community from a traditional fermented milk beverage for approximately 100
generations, with or without, repeated introduction of Escherichia coli at
each transfer. Community function was determined by metabolic profiling,
and we observed alterations therein immediately after E. coli
introduction, followed by recovery, or rebound once ceased. In contrast to
this proxy of community function, changes in the bacterial community
composition were never detected. Our results evidence that community
composition and function do not necessarily respond in parallel to an
introduced species, potentially due to genotypic changes below species
level detection or metabolic plasticity. Our work shows an ability for
functional recovery in microbial communities and contributes insight on
long-term community stability to sustained disturbances.