Exploring the functional and genomic features of Cellulophaga lytica NFXS1, a zeaxanthin and lytic enzyme-producing marine bacterium that promotes microalgae growth

Beneficial microalgae-bacteria interactions mediate important marine ecological processes and present potential for exploitation in the industrial production of microalgae. Members of the bacterial genus Cellulophaga are known for their ability to interact with several marine organisms, including microalgae, however, not much is understood about their properties. In this work we present the detailed characterization of the marine bacterium, Cellulophaga lytica NFXS1, including its ability to synthesize valuable compounds such as zeaxanthin, its ability to modulate the growth and productivity of two relevant marine microalgae, Nannochloropsis oceanica and Phaeodactylum tricornutum, and the analysis of its complete genome sequence. The obtained results showed that C. lytica NFXS1 used several complex carbohydrates, indicating strong lytic enzymatic activities. Additionally, co-cultivation studies revealed that C. lytica NFXS1 colonized the microalgae phycosphere, catabolized microalgae exudates, promoted the growth of microalgae, and increased fucoxanthin productivity in P. tricornutum. Genomic analysis revealed the basis for the microalgae growth-promoting activities of strain NFXS1, which are mostly mediated by gliding motility, biofilm formation, biosynthesis of phytohormones (auxins, cytokinins), polyamine biosynthesis, and resistance to oxidative stress induced by zeaxanthin production and ROS detoxifying enzymes. A vast array of genes encoding glycosyl hydrolases and pectate lyase family enzymes were also found in the NFXS1 chromosome. Overall, these findings brought new information regarding the properties of C. lytica NFXS1, which can be used as a model organism to study microalgae-bacteria interactions and is a strong candidate for the development of a wide range of marine biotechnological solutions.