Abstract
Different microbial communities are impacted disproportionately by environmental disturbances. The degree to which a community can remain stable when faced with a disturbance is referred to as resistance. However, the contributing ecological factors, which infer a community’s resistance are unknown. In this study, we investigate the impact of historical environmental stability on ecological phenomena and in turn, microbial community resistance to shocks. Three separate methanogenic consortia, which were subjected to varying degrees of historical environmental stability, and displayed different levels of resistance to an organic overload were sampled. Their community composition was assessed using high throughput sequencing of 16S rRNA genes and assembly based metagenomics. A suite of ecological analysis were applied to determine the effect of environmental stability on ecological phenomena such as microbial community assembly, microbial niche breadth and the rare biosphere and in turn, the effect of these phenomena on community resistance. Additionally, metagenome assembled genomes were analysed for functional effects of prolonged stability/instability. The system which was subjected to more environmental instability experienced more temporal variation in community beta diversity and a proliferation of specialists, with more abundant two component regulatory systems. This community was more susceptible to deterministic community assembly processes caused by a large environmental disturbance. These results imply that microbial communities experiencing longer term environmental instability (e.g. variations in pH or temperature) are less able to resist a large disturbances.