Light signaling in cyanobacteria

Molecular to physiology, ecology, and evolution

I’m fascinated with how molecules such as DNA, RNA, and proteins underpin the life of organisms. I love microorganisms because they are easy to handle with as a research target and also because these “lower” organism can show us their sophisticated orchestration of molecules than we “higher” organisms expect. My favorite organisms are cyanobacteria. They can grow photoautotrophically with oxygenic photosynthesis, with absorbing CO₂ and emitting oxygen. They are present in various niches on the earth, such as freshwater lakes, rivers, soils, rocks, hot springs, glaciers, and oceans. For cyanobacteria, light is not only an environmental signal but also an energy source. It is not surprising if we can find cyanobacteria elegantly utilize light information. Light is obviously one of the most fundamental environmental factors to control and affect the behavior of organisms. I am studying what happens in cyanobacterial cells when they sense a light environment.

Specifically, I have utilized thermophilic cyanobacterium Thermosynechococcus as a target organism. Many cyanobacteria have cyanobacteria-specific photoreceptors called “cyanobacteriochromes”. I have previously revealed that the three cyanobacteriochromes cooperatively regulate Thermosynechococcus cell aggregation in a light color-sensitive manner (see e.g. Enomoto 2015). This light signaling involves a nucleotide second messenger molecule called “c-di-GMP”. I am now investigating how dynamic behaviors of cyanobacteriochrome proteins and c-di-GMP molecules govern the cellular lifestyle as an EMBO Long-Term fellowship project.

I am also interested in the molecular studies in an ecology/evolution-relevant context. So far most of these analyses are done under constant cultivation conditions using axenic culture. In nature, however, any organism survives under fluctuating conditions with some “foreign friends”. It would be exciting if we can understand the behaviors and functions of molecules under their native niches.