Trait based approaches to microbial dormancy

Background/Question/Methods

Microbial communities are often comprised of thousands of potentially interacting species that carry out essential ecosystem processes. Insight into the assembly and maintenance of these complex communities may be gained by studying the functional traits of microorganisms. One trait that seems to be particularly important for maintaining diversity is the ability for microorganisms to enter a reversible state of reduced metabolic activity, or dormancy. Our previous work has demonstrated that the success of dormancy as a life history strategy is strongly influenced by the amount of time that individuals can persist prior to being resuscitated. A variety of persistence strategies are thought to have evolved among bacteria, which might have different costs and trade-offs. To test these general expectations, we quantified persistence for a phylogenetically diverse collection of soil bacteria in response to long-term starvation.

Results/Conclusions

Death curves revealed that there was approximately two orders of magnitude variation among strains in response to starvation. Some strains persisted with almost no loss of viability over the course of more than two years, while other strains rapidly succumbed to energy limitation. Interestingly, for the majority of our strains, the decay rate of viability significantly deviated from first-order expectations suggesting that bacterial death rates declined over time. Simulation models indicate that this type of functional response could not arise from cannibalism alone. Rather, our models suggest that the death rates and growth efficiencies of starving bacteria change through time, perhaps in an adaptive manner. Our results suggest that there are divergent eco-evolutionary strategies for dormancy that are important for the size and composition of microbial seed banks