Autogenous regulation and kinetics of induction of Pseudomonas aeruginosa recA transcription as analyzed with operon fusions
A promoterless chloramphenicol acetyltransferase gene (cat) was used to construct recA-cat operon fusions to quantitatively examine the transcriptional regulation of the Pseudomonas aeruginosa recA gene in P. aeruginosa PAO. Wild-type P. aeruginosa containing the recA8-cat fusion was treated with methyl methanesulfonate (MMS) and showed immediate induction of chloramphenicol acetyltransferase (CAT) specific activity, whereas a recA::Tn501 mutant of P. aeruginosa containing recA8-cat showed no induction with MMS. This indicated that a functional copy of recA was required for derepression of recA transcription and that P. aeruginosa recA protein was a positive regulatory factor promoting its own expression. Compared with that in the wild type, the uninduced level of CAT in recA8-cat-containing cells was reduced by approximately one-half in the recA::Tn501 mutant, indicating that recA+-dependent spontaneous induction contributes to the uninduced levels of recA expression in P. aeruginosa. MMS (0.012%) caused recA-directed CAT synthesis to increase almost immediately, with maximum CAT activity, fourfold higher than uninduced levels, attained at 60 min postinduction. The kinetics of recA8-cat fusion activity were shown to be directly related to the MMS doses used. Another fusion called recAa1-cat, where cat was located between the two transcriptional terminators of the P. aeruginosa recA gene, also showed dose-dependent induction by MMS, but the CAT activity from recAa1-cat was only one-half of that obtained with recA8-cat under the same conditions. Treatment of recA+ P. aeruginosa containing recA8-cat with UV irradiation produced an immediate effect on recA8-cat transcription and showed little UV dose dependency at doses of 5 J/m2 or greater.
- Research Organization:
- Univ. of California, Berkeley (USA)
- OSTI ID:
- 6796451
- Journal Information:
- J. Bacteriol.; (United States), Journal Name: J. Bacteriol.; (United States) Vol. 170:10; ISSN JOBAA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
560300* -- Chemicals Metabolism & Toxicology
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
BACTERIA
BIOLOGICAL EFFECTS
BIOLOGICAL RADIATION EFFECTS
DOSE-RESPONSE RELATIONSHIPS
ELECTROMAGNETIC RADIATION
ENZYME ACTIVITY
ENZYMES
ESTERS
GENE REGULATION
GENETIC EFFECTS
GENETIC RADIATION EFFECTS
METHYL METHANESULFONATE
MICROORGANISMS
MUTAGENS
MUTATIONS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
PSEUDOMONAS
RADIATION EFFECTS
RADIATIONS
RADIOINDUCTION
SULFONIC ACID ESTERS
TRANSCRIPTION
TRANSFERASES
ULTRAVIOLET RADIATION