Mechanism for iron control of theVibrio fischeri luminescence system: Involvement of cyclic AMP and cyclic AMP receptor protein and modulation of DNA level
✍ Scribed by Dunlap, Paul V.
- Publisher
- John Wiley and Sons
- Year
- 1992
- Weight
- 914 KB
- Volume
- 7
- Category
- Article
- ISSN
- 0884-3996
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✦ Synopsis
Iron controls luminescence in Vibrio fischeri by an indirect but undefined mechanism. To gain insight into that mechanism, the involvement of cyclic AMP (CAMP) and cAMP receptor protein (CRP) and of modulation of DNA levels in iron control of luminescence were examined in V. fischeri and i n Escherichia coli containing the cloned V. fischeri lux genes on plasmids. For V. fischeri and E. coli adenylate cyclase (cya) and CRP (crp) mutants containing intact lux genes (IuxR IuxlCDABEG). presence of the iron chelator ethylenediamine-di(o-hydroxyphenyl acetic acid) (EDDHA) increased expression of the luminescence system like in the parent strains only in the cya mutants in the presence of added CAMP. In the E. coli strains containing a plasmid with a M u dl(1acZ) fusion in IuxR, levels of p-galactosidase activity (expression from the IuxR promoter) and luciferase activity (expression from the lux operon promoter) were both 2-3-fold higher i n the presence o f EDDHA in the parent strain, and for the mutants this response t o EDDHA was observed only in the cya mutant in the presence of added CAMP. Therefore, cAMP and CRP are required for the iron restriction effect on luminescence, and their involvement in iron control apparently is distinct from the known differential control of transcription from the luxR and IuxlCDABEG promoters by CAMP-CRP. Furthermore, plasmid and chromosomal DNA levels were higher i n E. coli and V. fischeri in the presence of EDDHA. The higher DNA levels correlated w i t h an increase in expression of chromosomally encoded p-galactosidase in E. coli and with a higher level of autoinducer in cultures of V. fischeri. These results implicate CAMP-CRP and modulation of DNA levels in the mechanism of iron control of the V. fischeri luminescence system.