This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Dunlap, P V Articles by Kuo, A Search for Related Content PubMed PubMed Citation Articles by Dunlap, P V Articles by Kuo, A

research-article

Cell density-dependent modulation of the Vibrio fischeri luminescence system in the absence of autoinducer and LuxR protein.

Biology Department, Woods Hole Oceanographic Institution, Massachusetts 02543.

ABSTRACT

Expression of the Vibrio fischeri luminescence genes (luxR and luxICDABEG) in Escherichia coli requires autoinducer (N-3-oxohexanoyl homoserine lactone) and LuxR protein, which activate transcription of luxICDABEG (genes for autoinducer synthase and the luminescence enzymes), and cyclic AMP (cAMP) and cAMP receptor protein (CRP), which activate transcription of the divergently expressed luxR gene. In E. coli and in V. fischeri, the autoinducer-LuxR protein-dependent induction of luxICDABEG transcription (called autoinduction) is delayed by glucose, whereas it is promoted by iron restriction, but the mechanisms for these effects are not clear. To examine in V. fischeri control of lux gene expression by autoinducer, cAMP, glucose, and iron, lux::Mu dI(lacZ) and lux deletion mutants of V. fischeri were constructed by conjugation and gene replacement procedures. beta-Galactosidase synthesis in a luxC::lacZ mutant exhibited autoinduction. In a luxR::lacZ mutant, complementation by the luxR gene was necessary for luminescence, and addition of cAMP increased beta-galactosidase activity four- to sixfold. Furthermore, a luxI::lacZ mutant produced no detectable autoinducer but responded to its addition with induced synthesis of beta-galactosidase. These results confirm in V. fischeri key features of lux gene regulation derived from studies with E. coli. However, beta-galactosidase specific activity in the luxI::lacZ mutant, without added autoinducer, exhibited an eight- to tenfold decrease and rise back during growth, as did beta-galactosidase and luciferase specific activities in the luxR::lacZ mutant and luciferase specific activity in a delta(luxR luxICD) mutant. The presence of glucose delayed the rise back in beta-galactosidase and luciferase specific activities in these strains, whereas iron restriction promoted it. Thus, in addition to transcriptional control by autoinducer and LuxR protein, the V. fischeri lux system exhibits a cell density-dependent modulation of expression that does not require autoinducer, LuxR protein, or known lux regulatory sites. The response of autoinducer-LuxR protein-independent modulation to glucose and iron may account for how these environmental factors control lux gene expressions.

This article has been cited by other articles:

• Qin, N., Callahan, S. M., Dunlap, P. V., Stevens, A. M. (2007). Analysis of LuxR Regulon Gene Expression during Quorum Sensing in Vibrio fischeri. J. Bacteriol. 189: 4127-4134 [Abstract] [Full Text]  
• Sha, J., Lu, M., Chopra, A. K. (2001). Regulation of the Cytotoxic Enterotoxin Gene in Aeromonas hydrophila: Characterization of an Iron Uptake Regulator. Infect. Immun. 69: 6370-6381 [Abstract] [Full Text]  
• Visick, K. L., Foster, J., Doino, J., McFall-Ngai, M., Ruby, E. G. (2000). Vibrio fischeri lux Genes Play an Important Role in Colonization and Development of the Host Light Organ. J. Bacteriol. 182: 4578-4586 [Abstract] [Full Text]  
• Callahan, S. M., Dunlap, P. V. (2000). LuxR- and Acyl-Homoserine-Lactone-Controlled Non-lux Genes Define a Quorum-Sensing Regulon in Vibrio fischeri. J. Bacteriol. 182: 2811-2822 [Abstract] [Full Text]  
• Piper, K. R., Farrand, S. K. (2000). Quorum Sensing but Not Autoinduction of Ti Plasmid Conjugal Transfer Requires Control by the Opine Regulon and the Antiactivator TraM. J. Bacteriol. 182: 1080-1088 [Abstract] [Full Text]  
• Huisman, G., Kolter, R (1994). Sensing starvation: a homoserine lactone--dependent signaling pathway in Escherichia coli. Science 265: 537-539 [Abstract]