Transcriptional analysis of a gene cluster involved in glucose tolerance in Zymomonas mobilis: evidence for an osmoregulated promoter.
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 P(glc), 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.
Christogianni
Anastasia
A
Sector of Organic Chemistry and Biochemistry, Department of Chemistry, University of Ioannina, 45110 Ioannina, Greece.
Douka
Eugenia
E
Koukkou
Anna I
AI
Hatziloukas
Efstathios
E
Drainas
Constantin
C
D000595:Amino Acid Sequence; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D005947:Glucose / Q000378:metabolism*; D008969:Molecular Sequence Data; D005810:Multigene Family; D016366:Open Reading Frames; D009876:Operon; D011401:Promoter Regions, Genetic; D016415:Sequence Alignment; D017355:Zymomonas / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*
D005947:Glucose