Patent ID: 7678558

Claim:
An isolated Bacteroides fragilis ( B. fragilis ) cell producing a native capsular polysaccharide selected from the group consisting of: polysaccharide A (PSA), polysaccharide B (PSB), polysaccharide D (PSD), polysaccharide E (PSE), polysaccharide F (PSF), polysaccharide G (PSG), and polysaccharide H (PSH), wherein the promoter controlling expression of the native biosynthetic genes of the native capsular polysaccharide is locked on, wherein the promoter is locked on by disabling expression of the endogenous res02 (multiple promoter invertase) gene, said gene comprising the nucleotide sequence of SEQ ID NO:1, wherein res02 expression is disabled such that the level of res02 polypeptide is insufficient for inverting the promoter of the native biosynthetic genes of said native capsular polysaccharide, wherein the res02 polypeptide comprises the amino acid sequence of SEQ ID NO:2, and wherein the res02 expression is disabled by res02 antisense nucleic acid.