Analysis of the wee gene cluster responsible for the biosynthesis of the polymeric bioemulsifier from the oil-degrading strain Acinetobacter Iwoffii RAG-1

A cluster (27 kbp) of genes responsible for the biosynthesis of the amphipathic, polysaccharide bioemulsifier emulsan from the oil-degrading Acinetobacter Iwoffii RAG-1 was isolated and characterized. The complete sequence of this cluster, termed wee, consisted of 20 ORFs. One set of 17 ORFs was transcribed in one direction, while a second set of three ORFs, 607 bp upstream of the first, was transcribed in the opposite direction. Mutations in either of the two regions caused defects in emulsan production, yielding specific activities of 5-14% of parental emulsifying activity. Putative functions could be assigned to proteins involved in production of nucleotide amino sugar precursors, transglycosylation, transacetylation, polymerization and transport. However, no JUMPstart or ops sequences, normally found associated with some polysaccharide biosynthetic gene clusters, were identified. Evidence is presented suggesting that the bioemulsifier may be a member of the group 1 or group 4 polysaccharides.