Genomic insights into carbohydrate-active enzymes in a novel Radiobacillus strain from the Antarctic red macroalga Pyropia endiviifolia.

In this study, we analysed the genome of Radiobacillus sp. PE A8.2, an endospore-forming bacterium isolated from the surface of the Antarctic red seaweed Pyropia endiviifolia. Combined 16 S rRNA gene phylogeny and phylogenomic analyses, including Average Nucleotide Identity (ANI), indicate that strain PE A8.2 represents a putative novel species within the rare genus Radiobacillus. The PE A8.2 genome is a circular chromosome of 5.18 Mb in size. Annotated genes were primarily associated with core metabolic processes, and the abundance of transporter systems and regulatory enzymes highlights a strong capacity for substrate uptake and metabolic versatility. Additionally, we discovered a circular plasmid of approximately 10 kb, which contains multiple carbohydrate-active genes, suggesting a potential role in polysaccharide degradation. The PE A8.2 genome putatively encodes 220 CAZyme genes. Moreover, PE A8.2 is distinguished by a rich complement of CAZymes associated with algal polysaccharide degradation, including several glycoside hydrolase families linked to carrageenan, a trait rarely reported in Gram-positive bacteria. As a putative novel species, Radiobacillus sp. PE A8.2 represents a valuable resource for biotechnology, particularly for the discovery of new carbohydrate-degrading enzymes.