Patent ID: 7803602

Claim:
An isolated Bacteroides fragilis bacterial cell producing a native capsular polysaccharide A (PSA), and having a native promoter that controls expression of native biosynthetic genes of PSA and native promoters that control expression of native biosynthetic genes of native capsular polysaccharides PSB, PSD, PSE, PSF, PSG and PSH, wherein the promoter that controls expression of the native biosynthetic genes of PSA is locked on, wherein at least one of the promoters that controls expression of the native biosynthetic genes of the native capsular polysaccharides selected from the group consisting of: PSB, PSD, PSE, PSF, PSG, and PSH is locked off, wherein the promoter controlling expression of the native biosynthetic genes of PSA is locked on by altering at least one inverted repeat flanking the promoter controlling expression of the native biosynthetic genes of PSA such that inversion of the promoter is not possible, and wherein the inverted repeat comprises SEQ ID NO:7.