Thermosynechococcus switches the direction of phototaxis by a c-di-GMP-dependent process with high spatial resolution

Abstract

Many cyanobacteria, which use light as an energy source via photosynthesis, show directional movement towards or away from a light source. However, the molecular and cell biological mechanisms for switching the direction of movement remain unclear. Here, we visualized type IV pilus-dependent cell movement in the rod-shaped thermophilic cyanobacterium Thermosynechococcus vulcanus using optical microscopy at physiological temperature and light conditions. Positive and negative phototaxis were controlled on a short time scale of 1 min. The cells smoothly moved over solid surfaces towards green light, but the direction was switched to backward movement when we applied additional blue light illumination. The switching was mediated by three photoreceptors, SesA, SesB, and SesC, which have cyanobacteriochrome photosensory domains and synthesis/degradation activity of the bacterial second messenger cyclic dimeric GMP (c-di-GMP). Our results suggest that the decision-making process for directional switching in phototaxis involves light-dependent changes in the cellular concentration of c-di-GMP. Direct visualization of type IV pilus filaments revealed that rod-shaped cells can move perpendicular to the light vector, indicating that the polarity can be controlled not only by pole-to-pole regulation but also within-a-pole regulation. This study provides insights into previously undescribed rapid bacterial polarity regulation via second messenger signalling with high spatial resolution.

Cell surface architecture of the cultivated DPANN archaeonNanobdella aerobiophila

“…The cell motility of strains MJ1 T and MJ1HA was observed at 65ºC using a live-imaging system. The cell culture was poured into a tunnel chamber assembled by taping a coverslip, and both ends of the chamber were sealed with nail polish to keep from drying the sample, as previously described (29). Cell behavior was visualized under an inverted microscope (IX71, Olympus) equipped with an objective lens (LUCPLFLN 40×PH, Olympus), a CMOS camera (DMK33U174, Imaging Source, Germany), and an optical table (HAX-0806, JVI, Japan).…”

Light, Matter, Action: Shining Light on Active Matter

“…Optimal light conditions are crucial for microorganism, e.g. cyanobacteria, that grow by capturing energy from sunlight. They demonstrate positive phototaxis toward green light as it is their preferred energy source for oxygenic photosynthesis, while they show negative phototaxis away from strong light or UV light as it causes cell damage .…”

“…cyanobacteria, that grow by capturing energy from sunlight. They demonstrate positive phototaxis toward green light as it is their preferred energy source for oxygenic photosynthesis, while they show negative phototaxis away from strong light or UV light as it causes cell damage . Similarly, marine zooplankton Platynereis larvae exposed to UV light swim downward, away from the light source, while cyan light makes the larvae swim in the reverse, upward direction .…”

Light, Matter, Action: Shining light on active matter

“…Optimal light conditions crucial for microorganism, e.g. cyanobacteria, 104 that grow by capturing energy from sunlight. They demonstrate positive phototaxis towards green light as it is their preferred energy source for oxygenic photosynthesis, while they show negative phototaxis away from strong light or UV light as it causes cell damage.…”

“…They demonstrate positive phototaxis towards green light as it is their preferred energy source for oxygenic photosynthesis, while they show negative phototaxis away from strong light or UV light as it causes cell damage. 104 Similarly, marine zooplankton Platynereis larvae exposed to UV light swim downwards, away from the light source, while cyan light makes the larvae swim in the reverse, upwards direction. 105 In the ocean, UV light is most intense near the surface, while cyan light reaches greater depths.…”