Abstract
Magnetotactic bacteria utilize magnetosomes to navigate along magnetic fields and employ photosensitive proteins to respond to light. However, whether a synergistic mechanism exists between phototaxis and magnetotaxis remains unclear. To investigate the cooperative roles of the magnetosensitive protein Amb0994 and the photosensitive protein Amb2291 under magnetic reversal and coupled magneto-optical conditions, we conducted a comparative analysis of Magnetospirillum magneticum AMB-1 wild-type and mutant strains (Δamb0994, Δamb2291, Δamb0994Δamb2291). Experimental results demonstrated that wild-type strains exhibited consistent magnetotaxis responses under both illuminated and control (no added light) conditions, suggesting balanced signal integration via protein synergy. The Δamb0994 mutant exhibited accelerated magnetotaxis responses, indicating that Amb0994 normally functions to moderate magnetic signal processing. In contrast, the Δamb2291 mutant showed prolonged reversal times and lacked directional selectivity after illumination, implying Amb2291 functions as a "photo-directionality sensor." The double mutant displayed the slowest responses. Further, gene expression analysis of chemotaxis and flagellar genes revealed that the Amb0994 and Amb2291 proteins act as repressors in a bidirectional inhibitory equilibrium model, which converges on shared downstream effectors to control "U-turn" behavior. Based on these findings, we extended the motion simulation model framework to provide a phenomenological explanation for the magneto-optical response. Together, these results elucidate potential mechanisms of magneto-optical signal synergy in magnetotactic bacteria and offer new insights into the evolution of microbial taxis behaviors.