Complete genome sequence of Polaribacter sejongensis NJDZ03 exhibiting diverse macroalgal polysaccharide-degrading activity

A macroalgal polysaccharide-degrading bacterial strain, Polaribacter sejongensis NJDZ03, was isolated from the surface of a species of Desmarestia, a seaweed genus endemic to Antarctica. To explore the mechanism underlying the multiple polysaccharide-degrading abilities of this strain, we sequenced and analyzed its complete genome. We found that the genome comprises a 4,078,668 bp circular chromosome containing 3484 coding genes, including 18 rRNA operons whose genes are arranged in the order of 16S-23S-5S rRNA. Gene annotation revealed the existence of three putative polysaccharide utilization loci (PULs) consisting of several agarase, carrangeenase, and alginate lyase genes, repectively. These PULs are likely responsible for the strong agar-, alginate-, and carrageenan-degrading capabilities of P. sejongensis NJDZ03, especially its ability to degrade diverse carrageenans, including κ-carrageenan, τ-carrageenan, and λ-carrageenan. Our findings should provide new insights into the carbon cycle of the Antarctic oceanic ecosystem.