THE ISPB GENE ENCODING OCTAPRENYL DIPHOSPHATE SYNTHASE IS ESSENTIAL FOR GROWTH OF ESCHERICHIA-COLI

The Escherichia coli ispB gene encoding octaprenyl diphosphate synthas e is responsible for the synthesis of the side chain of isoprenoid qui nones, We tried to construct an E. coli ispB-disrupted mutant but coul d not isolate the chromosomal ispB disrupted mutant unless the ispB ge ne or its homolog was supplied on a plasmid, The chromosomal ispR disr uptants that harbored plasmids carrying the ispR homologs from Haemoph ilus influenzae and Synechocystis sp, strain PCC6803 produced mainly u biquinone 7 and ubiquinoue 9, respectively, Our results indicate that the function of the ispB gene is essential for normal growth and that this function can be substituted for by homologs of the ispB gene from other organisms that produce distinct forms of ubiquinone.