The invention relates to a fragment of DNA containing genes encoding the synthesis of the O-antigen of Vibrio cholerae serotypes Inaba or Ogawa and being at least 16 kb in length. The invention further related to a cosmid comprising a cloned DNA fragment containing genes encoding the synthesis of O-antigen of Vibrio cholerae serotypes Inaba or Ogawa and to a strain of E.coli that includes the fragment.
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