Phototaxis: Microbial

Abstract

Phototaxis in its broadest sense is light‐regulated movement of motile organisms (microorganisms in the case of microbial phototaxis), usually resulting in their attraction to (positive phototaxis) or avoidance of (negative phototaxis) illuminated regions. Prokaryotes often use a time‐biased random walk strategy under which they choose directions randomly, but move for longer time periods in the chosen direction when that direction happens to be correct. They use type I sensory rhodopsin photoreceptors and two‐component histidine kinase‐mediated phosphotransfer systems to regulate flagellar movement. Eukaryotic microbes by contrast can sense and respond to the direction of light by regulating the direction of movement. Phototransduction pathways in eukaryotic microbes appear to involve protein phosphorylation/dephosphorylation at serine or threonine residues, and the responsible kinases and phosphatases are regulated by second messengers. This review focuses on select representative organisms from each of the three taxonomic domains whose photosensory signal transduction pathways have been studied. Although many components of the signal transduction pathways controlling phototaxis have been identified, there is still much to be elucidated. Key Concepts: Phototaxis enables microorganisms to position themselves in an environment that is optimal for survival. Organisms from all three taxonomic domains display phototaxis with differing photosensory signal transduction pathways. Photosensory signal transduction pathways in eubacteria and archaea involve the coupling of signals from photoreceptors to the same signalling pathways as are used by these organisms for chemotaxis. Phototransduction pathways in eukaryotic microbes appear to involve protein phosphorylation/dephosphorylation at serine or threonine residues, and the responsible kinases and phosphatases are regulated by second messengers.

Comparing the diel vertical migration of Karlodinium veneficum (dinophyceae) and Chattonella subsalsa (Raphidophyceae): PSII photochemistry, circadian control, and carbon assimilation

“…has a circadian period). DVM is particularly complex because it integrates a wide variety of cellular physiologies into a plastic behavior [17], via the use of a variety of sensory perceptions [51], which operate by incompletely characterized signal transduction pathways [1]. In this regard, understanding how DVM is employed by different algal species could be useful to better characterize their ecological niches [17].…”