Description
Light is a key environmental cue shaping microbial dynamics in the ocean, yet its role in regulating bacterial motility remains poorly understood. As part of a study exploring light-mediated microbial interactions within the phycosphere, we investigated the behavioral response of the marine bacterium Alteromonas macleodii to controlled illumination. Using high-speed video microscopy and microfluidic chambers, we observed a marked increase in swimming speed upon exposure to blue light (455 nm). This photoresponse was wavelength-specific, as no comparable effect was detected under red light. These findings suggest that A. macleodii possesses a functional blue-light sensory pathway influencing its motility, potentially mediated by flavin-based photoreceptors such as BLUF or LOV-domain proteins. Given the ecological ubiquity of A. macleodii, such light-dependent behavioral plasticity could have important implications for microbial positioning, nutrient acquisition, and interactions within the illuminated layers of the ocean. Ongoing work tests how this photoresponse varies under different light regimes and across distinct phases of the bacterial life cycle, as well as how light sensitivity shapes behavior in complex optical microenvironments mimicking the phycosphere. Together, these results reveal light as a dynamic regulator of bacterial motility and microscale ecological interactions.