Assignment of genes in the alginate biosynthesis operon of P. aeruginosa and their homologs in Nitratiruptor sp. SB155-2. Genes encoding proteins with homology between P. aeruginosa and Nitratiruptor sp. SB155-2 are connected by dotted lines. Each pentagon is classified by a different color based on known function in P. aeruginosa as follows: blue, precursor biosynthesis; green, alginate polymerization; brown, alginate export; violet, epimerization of mannuronic acid to guluronic acid; red, alginate degradation; gray, O-acetylation. Yellow pentagons show genes with unidentified functions in Nitratiruptor sp. SB155-2.