OOS 26-5
Apply ecological rules to microbial communities in industrial and engineered habitats
Engineered habitats are no more than islands where we can observe, test and apply the rules of community formation and dynamics for pleasure and profit. Indeed engineers, entrepreneurs and synthetic biologists ignore those rules at their peril.
Results/Conclusions
It transpires that, on average, such reactors faithfully obey the precepts of simple neutral models. Though the patterns first seen in sewage works have been subsequently seen in many natural environments. Calibrating and applying those rules tells us many things. Not least that, though the rules for microbial systems may be the same as those in conventional ecology, the outcomes are not. For microbes work at vastly larger scales. Thus, the rates of immigration scale with the community size; but microbial communities are so vast that immigration declines to the point that they are physically open and yet ecologically closed. Or the taxa-area curve, far from being “the oldest law in ecology” is but a pattern contingent on the numbers of individuals in the system and the diversity of the metacommunity from which they are assembled. The diversity of that metacommunity may very well be related to the free-energy available from the group’s characteristic redox couple. This implies that this free energy somehow affects the rate of evolution.
However, whilst a taxon may be close to neutral on average, on any given day it is not. Taxa oscillate around a mean driven by a mixture of “niche” environmental factors and “stochastic” drift which we are currently partitioning by examining the dynamics of 12 reactors operated in parallel. Though the relative importance of drift and environment is still emerging, what is clear is that the mean net growth rate for all taxa is zero. All taxa hold essentially the same mean long-term abundance, in engineered system for years, perhaps in “real” systems for millennia. This suggests that the debate about the relative importance of “niche and neutral” may be secondary to the question of why a taxon is able to maintain the same long-term abundance ad-infinitum. We posit that the idea of an organism having a niche is not helpful. All an organism has is its genome. A genome is a strategy that delivers benefits and incurs costs. A genome is a success if its benefits, on average, equal its costs: in which case it will sustain the same long-term abundance. The genomes with the most successful strategies will become the most abundant taxa.