Identification of bacteriophage K20 binding regions of OmpF and lipopolysaccharide in Esherichia coli K-12

Two classes of phage K20 resistant Escherichia coli K-12 mutants were obtai ned. One class of mutants possessed alterations within the ompF gene while the rfa gene cluster, which is responsible for lipopolysaccharide (LPS) syn thesis, was affected in the second class of mutants. The OmpF mutants conta ined substitutions affecting residues localized within the surface-exposed loops 5, 6 or 7. A single deletion mutation resulted in the removal of eigh t residues of loop 5. These alterations prevented the binding of K20 to cel l surface without affecting OmpF's channel activity. One LPS mutant charact erized in detail contained an unusual aberration within the rfa gene cluste r caused by an IS5 element. Its insertion mediated a deletion encompassing the rfaBIJ genes. Genetic complementation analysis revealed that the rfaB g ene, whose product catalyzes the addition of a galactose residue to the fir st glucose molecule of the LPS core, is necessary to synthesize LPS able to serve as a co-receptor for phage K20. (C) 1999 Federation of European Micr obiological Societies. Published by Elsevier Science B.V. All rights reserv ed.