GENES ENCODING HOMOLOGS OF 3 CONSECUTIVE ENZYMES IN THE BUTYRATE BUTANOL-PRODUCING PATHWAY OF CLOSTRIDIUM-ACETOBUTYLICUM ARE CLUSTERED ON THE CLOSTRIDIUM-DIFFICILE CHROMOSOME/

Screening of a Clostridium difficile lambda EMBL3 gene library with an tisera raised against C. difficile culture supernatant identified seve ral clones expressing a 31-kDa protein. A 1.8-kb HindIII fragment subc loned from one of the clones was sufficient for expression of the 31-k Da polypeptide. Southern blot analysis showed a region homologous to t his fragment robe present in all of 13 different C. difficile strains tested. Sequence analysis of the 1.8-kb fragment revealed three adjace nt open reading frames. A database search showed that these three open reading frames appeared to encode homologues of three consecutive enz ymes in the butanol/butyrate-producing pathway of Clostridium acetobut ylicum (crotonase, beta-hydroxybutyryl coenzyme A dehyrogenase and thi olase).