Frequency of disturbance alters diversity, function, and underlying assembly mechanisms of complex bacterial communities.
Santillan E, Seshan H, Constancias F, Drautz-Moses DI, Wuertz S
NPJ Biofilms Microbiomes. 2019. doi: 10.1038/s41522-019-0079-4
COMMENT: The authors tested the effect of disturbances on the structure, assembly and function of complex microbial communities. For that, they added toxic 3-choroaniline as disturbance to complex microbial communities within an engineered system with eight different frequency levels of augmentation, either never (L0, undisturbed), every 7, 6, 5, 4, 3, and 2 days (L1–6, intermediately-disturbed), or every day (L7, press-disturbed). They conclude that disturbance affects the ecosystem structure.
The objective of this work was to test the effect of disturbance on the bacterial community structure, diversity, and ecosystem function of a complex bacterial system, with emphasis on the underlying assembly mechanisms.
The undisturbed (L0) and press-disturbed (L7) levels were distinct from each other as well as from the remaining intermediate levels, as supported by multivariate tests.
The ecosystem function was clearly differentiated between L0 and L7, as well as being consistent across replicates at each level. We contend that the observed clustering is an indication that both the undisturbed and press-disturbed levels favoured deterministic assembly mechanisms, where the selective pressure due to unaltered succession (L0) or sustained toxic-stress (L7) promoted species sorting, resulting in similar community structuring among biological replicates over the course of the experiment.
We observed the highest α-diversity at intermediate levels as predicted by the IDH (Intermediate stochasticity hypothesis), both in terms of composition (0D) and abundances (1D, 2D)
Disturbances could promote stochastic assemblages of the sludge communities, which despite harbouring higher diversity could lead to variable overall ecosystem function. This could be the reason why after similar perturbations the process outcome differs, causing operational problems for water utilities. Furthermore, cases where disturbance temporally favours stochastic assembly could lead to a different final community after the perturbation, which could compromise the expected ecosystem function. More research is needed to identify such scenarios in practice.