Decision-making of the benthic diatom <i>Seminavis robusta</i> searching for inorganic nutrients and pheromones

Microorganisms encounter a diversity of chemical stimuli that trigger individual responses and influence population dynamics. However, microbial behavior under the influence of different incentives and microbial decision-making is poorly understood. Benthic marine diatoms that react to sexual attractants as well as to nutrient gradients face such multiple constraints. Here, we document and model behavioral complexity and context-sensitive responses of these motile unicellular algae to sex pheromones and the nutrient silicate. Throughout the life cycle of the model diatom Seminavis robusta nutrient-starved cells localize sources of silicate by combined chemokinetic and chemotactic motility. However, with an increasing need for sex to restore the initial cell size, a change in behavior favoring the attraction-pheromone-guided search for a mating partner takes place. When sex becomes inevitable to prevent cell death, safeguard mechanisms are abandoned, and cells prioritize the search for mating partners. Such selection processes help to explain biofilm organization and to understand species interactions in complex communities

Poster_MolecularMimicry_2017.pdf

Molecular mimicry is the formation of specific molecules by parasites to avoid recognition and suppression by the immune system of the host. This is analogous to uniforms misused by villains. Several pathogenic Ascomycota and Zygomycota show such a behaviour, deceiving, in particular, the innate immune system. For example,<i>Candida albicans</i> binds human regulators like complement factor H and, thus, hides from the complement system. Such a camouflage can reach a point where the immune system can no longer clearly distinguish between self and non-self. This implies that a trade-off between attacking possible pathogens and host cells has to be made, which can in turn lead to autoimmunity. Based on methods from signalling theory and protein-interaction modelling, we here present a model of molecular mimicry by <i>C. albicans</i><i> </i>involving human immune regulatory factor H

Genome-driven evolutionary game theory helps understand the rise of metabolic interdependencies in microbial communities

The rise of metabolic interdependencies among microbes is still poorly understood. Here, taking the underlying biochemical networks into consideration, Zomorrodi and Segrè integrate genome-scale metabolic models with evolutionary game theory to study the rise of cross-feeding in microbial communities

Orienting the Interaction Compass: Resource Availability as a Major Driver of Context Dependence

Life on earth is enormously diverse, in part because each individual engages in countless interactions with its biotic and abiotic environment during its lifetime. Not only are there many such interactions, but any given interaction of each individual with, say, its neighbor or a nutrient could lead to a different effect on its fitness and on the dynamics of the population of which it is a member. Predicting those effects is an enduring challenge to the field of ecology. Using a simple laboratory system, Hoek and colleagues present evidence that resource availability can be a primary driver of variation between interactions. Their results suggest that a complex continuum of interaction outcomes can result from the simple combined effects of nutrient availability and density-dependent population dynamics. The future is rich with potential to integrate tractable experimental systems like theirs with hypotheses derived from studies of interactions in natural communities

Decision-making of the benthic diatom Seminavis robusta searching for inorganic nutrients and pheromones

Microorganisms encounter a diversity of chemical stimuli that trigger individual responses and influence population dynamics. However, microbial behavior under the influence of different incentives and microbial decision-making is poorly understood. Benthic marine diatoms that react to sexual attractants as well as to nutrient gradients face such multiple constraints. Here, we document and model behavioral complexity and context-sensitive responses of these motile unicellular algae to sex pheromones and the nutrient silicate. Throughout the life cycle of the model diatom Seminavis robusta nutrientstarved cells localize sources of silicate by combined chemokinetic and chemotactic motility. However, with an increasing need for sex to restore the initial cell size, a change in behavior favoring the attraction-pheromone-guided search for a mating partner takes place. When sex becomes inevitable to prevent cell death, safeguard mechanisms are abandoned, and cells prioritize the search for mating partners. Such selection processes help to explain biofilm organization and to understand species interactions in complex communities