Current Microbiology

, Volume 35, Issue 6, pp 336–342 | Cite as

H-NS Protein Represses Transcription of the lux Systems of Vibrio fischeri and Other Luminous Bacteria Cloned into Escherichia coli

  • Shimon  Ulitzur
  • Abdul  Matin
  • Cress  Fraley
  • Edward  Meighen

Abstract.

High expression in Escherichia coli of the lux system cistron of a luminous bacteria under its own control has been accomplished only for the Vibrio fischeri lux system at high cell density. Mutation of the hns gene in E. coli has resulted in strong expression of the V. fischeri lux system at low cell density even in an rpoS-deleted strain of E. coli that emits very low levels of luminescence. The E. coli double mutant, MC4110 hns∝kan rpoS∝tet carrying the lux system of V. fischeri, developed high luminescence from the very early stages of cellular growth, regardless of the presence of deletion mutations in the luxI or luxR genes. Moreover, autoinducer synthesis was restored in the double mutant with the luxR-deleted system. plac-controlled V. fischeri luxCDABE genes missing luxI and luxR were dim in E. coli rpoS mutant cells, but had wild-type levels of light in the hns-deleted strain [MC4110 hns rpoS], showing that expression was independent of lux regulators in the absence of H-NS. DNA gyrase inhibitors and DNA intercalating agents also brought about the restoration of luminescence in the rpoS-deficient strain. High expression of the lux systems of Vibrio harveyi, Photobacterium leiognathi, and Xenorhabdus luminescens in E. coli MC4110 hns rpoS cells compared with that in wild-type or rpoS mutants was also accomplished. Taken together, these data suggest that the H-NS protein inhibits transcription in E. coli of the lux systems of all or most luminous bacteria at the luxC gene as well as in the luxRI region of the V. fischeri lux operon. These DNA regions are highly enriched with homopolymeric stretches of poly d(A) and poly d(T) characterizing curved DNA, a preferable site of H-NS binding. The significance of the new findings in understanding the regulatory control of the bacterial lux system is discussed.

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Copyright information

© Springer-Verlag New York Inc. 1997

Authors and Affiliations

  • Shimon  Ulitzur
    • 1
  • Abdul  Matin
    • 2
  • Cress  Fraley
    • 3
  • Edward  Meighen
    • 3
  1. 1.Faculty of Food Engineering and Biotechnology, Technion-Israel Institute of Technology, Technion City, Haifa 32000, Israel IL
  2. 2.Department of Microbiology and Immunology, Sherman Fairchild Science Building, Stanford University School of Medicine, Stanford, CA 94305-5402, USA US
  3. 3.Department of Biochemistry, McGill University, Montreal, Canada H3G1Y6 CA

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