Two kinds of mutants were isolated to clone a cluster of genes essential for zooglan biosynthesis. Zoogloea ramigera 115 strains produce capsular polysaccharide. To achieve conjugation in strain 115 and to facilitate recovery of product, a capsule non-forming strain was isolated via successive centrifugation and screening. The other kind of mutants devoid of or producing altered exopolysaccharides were obtained using classical transposon(Tn5) technique and screened for altered colony morphology and celluflour binding properties. Complementation of these mutants was achieved with Z. ramigera 115 slime gene library constructed in a broad host range cosmid vector and helper plasmid by triparental conjugation.