Temperature-driven nitrogen mixotrophy shapes marine cyanobacteria Prochlorococcus and Synechococcus latitudinal distribution pattern

Temperature, photosynthetically active radiation, and nutrient availability are pivotal in determining the global distribution of marine cyanobacteria. This study demonstrates that the distinct latitudinal niches of Synechococcus and Prochlorococcus are modulated by their temperature-dependent, mixotrophic nitrogen utilization strategies. Comparative genomic analysis reveals that Prochlorococcus ecotypes differ in their nitrogen transporter repertoire, with low-light ecotypes harboring ~12 transporters, while high-light ecotypes possess ~5 transporters. Conversely, Synechococcus displays greater genomic flexibility, with 17 nitrogen transporters. Reanalysis of Tara Oceans metatranscriptomic data identifies ~15 °C as a key thermal threshold for cyanobacterial distribution. In warmer regions (15-30°C, 35˚S-40˚N), Prochlorococcus optimizes nitrogen transporter functions across their ecotypes, whereas Synechococcus, leveraging its broad nitrogen transporters, exhibits functional plasticity, utilizing inorganic nitrogen in warmer waters and organic nitrogen in cooler waters ranging from -2°C to 15 °C beyond 35˚S/40˚N. Our findings underscore the critical role of temperature-driven mixotrophic nitrogen utilization in shaping the biogeographical patterns of marine cyanobacteria. Prochlorococcus and Synechococcus nitrogen utilisation strategies are regulated by temperature and drive species’ latitudinal distribution, according to the comparative genome analysis of marine cyanobacteria samples, combined with metagenomic and metatranscriptomic data.