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Flower nectar is a sugar-rich ephemeral habitat for microorganisms. Nectar-borne yeasts are part of the microbial community and can affect pollination by changing nectar chemistry, attractiveness to pollinators or flower temperature if yeast population densities are high. Pollinators act as dispersal agents in this system; however, pollination events lead potentially to shrinking nectar yeast populations. We here examine how sufficiently high cell densities of nectar yeast can develop in a flower. In laboratory experiments, we determined the remaining fraction of nectar yeast cells after nectar removal, and used honeybees to determine the number of transmitted yeast cells from one flower to the next. The results of these experiments directly fed into a simulation model providing an insight into movement and colonization ecology of nectar yeasts. We found that cell densities only reached an ecologically relevant size for an intermediate pollination probability. Too few pollination events reduce yeast inoculation rate and too many reduce yeast population size strongly. In addition, nectar yeasts need a trait combination of at least an intermediate growth rate and an intermediate remaining fraction to compensate for highly frequent decimations. Our results can be used to predict nectar yeast dispersal, growth and consequently their ecological effects. [ABSTRACT FROM AUTHOR]

Organisms are prone to different stressors and have evolved various defense mechanisms. One such defense mechanism is priming, where a mild preceding stress prepares the organism toward an improved stress response. This improved response can strongly vary, and primed organisms have been found to respond with one of three response strategies: a shorter delay to stress, a faster buildup of their response or a more intense response. However, a universal comparative assessment, which response is superior under a given environmental setting, is missing. We investigate the benefits of the three improved responses for microorganisms with an ordinary differential equation model, simulating the impact of an external stress on a microbial population that is either naïve or primed. We systematically assess the resulting population performance for different costs associated with priming and stress conditions. Our results show that independent of stress type and priming costs, the stronger primed response is most beneficial for longer stress phases, while the faster and earlier responses increase population performance and survival probability under short stresses. Competition increases priming benefits and promotes the early stress response. This dependence on the ecological context highlights the importance of including primed response strategies into microbial stress ecology. [ABSTRACT FROM AUTHOR]

Microbes in nature are exposed to complex environmental stressors which challenge their functioning or survival. Priming is the improved reaction of an organism to an environmental stressor following a preceding, often milder stress event. This phenomenon, also known as cross-protection, predictive response strategy or acquired stress resistance, is becoming an increasingly well-established research topic in microbiology, which has so far been examined from the perspective of a single organism or population. However, microbes in nature occur as part of communities; thus it is timely to highlight the need to also include this level beyond the individual species in studies of priming effects. We here introduce a conceptual framework for such studies at the level of the microbial assemblage and also chart a way forward for empirical and theoretical study. We illustrate some of the elements of our framework with a simple simulation model. Given the dynamic habitat of many microbes, incorporating priming is important for a more complete understanding of microbial community responses to stress. [ABSTRACT FROM AUTHOR]