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Journal of Bacteriology, August 2005, p. 5179-5188, Vol. 187, No. 15
0021-9193/05/$08.00+0     doi:10.1128/JB.187.15.5179-5188.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Transcriptional Analysis of a Gene Cluster Involved in Glucose Tolerance in Zymomonas mobilis: Evidence for an Osmoregulated Promoter

Anastasia Christogianni,1 Eugenia Douka,1 Anna I. Koukkou,1 Efstathios Hatziloukas,2 and Constantin Drainas1*

Sector of Organic Chemistry and Biochemistry, Department of Chemistry, University of Ioannina, 45110 Ioannina, Greece,1 Department of Biological Applications & Technologies, University of Ioannina, Dourouti, 45110 Ioannina, Greece2

Received 14 September 2004/ Accepted 16 February 2005

Exponentially growing cells of Zymomonas mobilis normally exhibit a lag period of up to 3 h when they are transferred from a liquid medium containing 2% glucose to a liquid medium containing 10% glucose. A mutant of Z. mobilis (CU1) exhibited a lag period of more than 20 h when it was grown under the same conditions, whereas it failed to grow on a solid medium containing 10% glucose. The glucose-defective phenotype of mutant CU1 was due to a spontaneous insertion in a putative gene (ORF4) identified as part of an operon (glc) which includes three additional putative genes (ORF1, ORF2, and ORF3) with no obvious involvement in the glucose tolerance mechanism. The common promoter controlling glc operon transcription, designated Pglc, was found to be osmoregulated and stimulated by the putative product of ORF4 in an autoregulated fashion, as indicated by expression of the gfp reporter gene. Additionally, reverse transcriptase PCR analysis showed that the gene cluster produces a single mRNA, which verified the operon organization of this transcription unit. Further transcriptional analysis demonstrated that glc operon expression is regulated by the concentration of glucose, which supported the hypothesis that this operon is directly involved in the uncharacterized glucose tolerance mechanism of Z. mobilis.

* Corresponding author. Mailing address: Sector of Organic Chemistry and Biochemistry, Department of Chemistry, University of Ioannina, 45110 Ioannina, Greece. Phone: 30-651-98372. Fax: 30-651-47832. E-mail: cdrainas{at}cc.uoi.gr.

Journal of Bacteriology, August 2005, p. 5179-5188, Vol. 187, No. 15
0021-9193/05/$08.00+0     doi:10.1128/JB.187.15.5179-5188.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.





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