A mutant of Gluconobacter oxydans deficient in gluconic acid dehydrogenase

Gluconobacter oxydans ATCC 9937 was subjected to transposon mutagenesis usi ng Tn5. A non-pigmented mutant was shown to be defective in gluconic acid d ehydrogenase and to produce gluconic acid from glucose, whereas the parent strain produced 2,5-diketogluconic acid. Cloning and sequencing of the regi on containing the Tn5 insertion showed that the insertion point occurred in an open reading frame homologous (42% amino acid identity) to the ribF gen es of Pseudomonas fluorescens and Escherichia coli. The resulting lack of a riboflavin cofactor would explain the loss of enzyme activity. (C) 1999 Pu blished by Elsevier Science B.V. All rights reserved.