Environmental adaptations by the intertidal Antarctic cyanobacterium Halotia branconii CENA392 as revealed using long-read genome sequencing

Antarctica poses numerous challenges to life such as cold shock, low nutrient concentrations, and periodic desiccation over a wide range of extreme temperatures. Cyanobacteria survive this harsh environment having evolved adaptive metabolic plasticity to become the dominant primary producers. The type strain cyanobacterium Halotia branconii CENA392 was isolated from an Antarctic intertidal seashore. The complete circular genome of this strain is presented herein, which was assembled using long-sequence reads. The genome encoded some stress-related genes associated with low-temperature adaptation and biosynthesis of mycosporine-like amino acid (MAA) photoprotective compounds. Empirical experimentation demonstrated constitutive production of the MAA porphyra-334 and total carotenoids without exposure to low temperatures or ultraviolet radiation stress. Phylogenetic analysis provided insights on taxonomic placement and evolutionary history of some annotated genes. These data exemplify the importance of generating complete quality genome sequences of microorganisms isolated from extreme intertidal environments, facilitating in-depth evaluation of ecological and taxonomic inferences.