title: Effect of iron on accumulation of exotoxin A-specific mRNA in Pseudomonas aeruginosa.
abstract: A DNA probe from an internal fragment of the exotoxin A structural gene was used to study the effects of selected culture conditions on steady-state levels of exotoxin-specific mRNA in Pseudomonas aeruginosa. Cells grown under conditions of iron deprivation began to synthesize and excrete the exotoxin A polypeptide during the late exponential phase of growth and throughout the stationary phase of growth, concomitant with a sharp increase in exotoxin A mRNA pools in P. aeruginosa cells. The addition of iron to the medium resulted in the failure of these cells to synthesize exotoxin A mRNA, despite significantly enhanced growth. The inhibition of the production of exotoxin A and the accumulation of its mRNA by iron was dose dependent, with a half-maximal inhibitory concentration of FeSO4 of 5 to 10 microM. A blockade of the initiation of transcription by rifampin resulted in the decay of exotoxin A mRNA, with a half-life of approximately 8 to 10 min, depending on the media used for growth. The addition of iron to cells actively engaged in exotoxin A synthesis also resulted in a gradual decrease in the amount of this mRNA in bacteria. However, the rate of decline of mRNA induced by iron was relatively slow (half-life, 90 min), with a considerable lag time between the iron addition and the first detectable effect on mRNA. While iron clearly appears to influence the production of exotoxin A at the transcriptional level, the molecular basis of this effect may involve several interacting factors affecting the initiation of transcription and perhaps mRNA turnover.
mesh_terms: D036002:ADP Ribose Transferases; D001427:Bacterial Toxins; D005098:Exotoxins / Q000096:biosynthesis*; D007501:Iron / Q000494:pharmacology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000378:metabolism*; D012329:RNA, Bacterial / Q000096:biosynthesis*; D012333:RNA, Messenger / Q000096:biosynthesis*; D014158:Transcription, Genetic / Q000187:drug effects; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A
chemical_list: D036002:ADP Ribose Transferases; D001427:Bacterial Toxins; D005098:Exotoxins; D007501:Iron; D012329:RNA, Bacterial; D012333:RNA, Messenger; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A