Environmental regulation of expression of virulence determinants in Bordetella pertussis.
The trans-activator vir is required for expression of all virulence-associated genes in Bordetella pertussis. The nature of the global regulation of these factors by vir and environmental signals was examined by Northern blot analysis and with beta-galactosidase transcriptional fusions in five vir-regulated genes. Northern blots suggested that vir regulates at the level of transcription since Vir- organisms did not exhibit detectable mRNA from vir-regulated loci. Environmental signals such as high levels of salts, nicotinic acid, and 6-chloronicotinic acid or growth at low temperatures were examined. Of all of the cations and anions examined, only SO4 ions eliminated transcription of vir-regulated genes and reduced transcription of vir itself, suggesting that global regulation is obtained by modifying expression of the essential component, vir. Organisms grown on 6-chloronicotinic acid or quinaldic acid did not have detectable transcription from vir-regulated loci. Modulation by nicotinic acid, on the other hand, was strain dependent, acting at the level of transcription in strain 18-323 but not in Tohama I derivatives. Growth at lower temperatures reduced, but did not eliminate, transcription from vir-regulated loci. At 28 degrees C the ratio of pertussis toxin mRNA to recA mRNA (a non-vir-regulated factor) was equivalent to that at 37 degrees C, suggesting that transcription at low temperatures is reduced in a proportional manner and need not involve vir.
Melton
A R
AR
Department of Microbiology and Immunology, Virginia Commonwealth University, Richmond 23298.
Weiss
A A
AA
D001886:Bordetella pertussis / Q000187:drug effects / Q000235:genetics* / Q000472:pathogenicity; D015870:Gene Expression / Q000187:drug effects; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial / Q000187:drug effects; D005809:Genes, Regulator; D005838:Genotype; D007477:Ions; D008834:Microclimate; D009525:Niacin / Q000494:pharmacology; D009994:Osmolar Concentration; D010641:Phenotype; D012329:RNA, Bacterial / Q000235:genetics / Q000302:isolation & purification; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics; D015183:Restriction Mapping; D013431:Sulfates / Q000494:pharmacology; D013696:Temperature; D014158:Transcription, Genetic / Q000187:drug effects; D014774:Virulence
D007477:Ions; D012329:RNA, Bacterial; D012333:RNA, Messenger; D013431:Sulfates; D009525:Niacin