Cyanobacteria can survive and flourish in a broad range of environments, and often dominate in marine habitats as well as in microbial mats and biofilms. Their ubiquitous global distribution reflects, in part, their ability to cope with wide fluctuations in temperature, nutrient, and light levels. Dr. Bhaya is particularly interested in the ability of cyanobacteria to perceive and move towards or away from a light source and thereby optimize conditions for photosynthesis. This project will help the scientific community understand the molecular basis of this critically important trait.
This phenomenon, termed phototaxis, is well-known but little understood. Recently Dr.Bhaya and her colleagues have demonstrated that phototaxis in Synechocystis is a surface-dependent phenomenon that requires type IV pili, surface appendages implicated in both twitching and social motility and the association of bacterial pathogens with their hosts. This investigator has taken advantage of the fact that the Synechocystis genome has been entirely sequenced to generate a library of tagged motility mutants. She will focus her work on a class of mutants that map to chemotaxis-like (che) genes. While the role of chemotaxis proteins is fairly well-understood in enteric bacteria, it is not clear whether many of the paradigms that have been established extend to the operation of Che proteins in other systems. Synechocystis has at least three che loci, two of which are involved in motility responses. Furthermore, one of the mutants that the investigator has isolated has a lesion in a gene encoding a protein with a domain reminiscent of the chromophore-binding domain of phytochrome in vascular plants. To elucidate the elements involved in generating and controlling motility, Dr.Bhaya will use time-lapse video microscopy to record movement in real time in both wild type and mutant strains. This will allow her to observe, for the first time, movement of single cells and cell populations, and thus to ask fundamental questions about the parameters that govern motility. The second aspect of the work is to use molecular and biochemical tools to tag and/or mutate specific proteins, such that the interactions among the proteins that regulate phototaxis can be better understood.
