Global transcriptional upregulation in the absence of increased translation in Chlamydia during IFN[gamma]-mediated host cell tryptophan starvation

• Published in: Molecular microbiology 2006-12, Vol.62 (5), p.1387
• Main Authors: Ouellette, Scot P, Hatch, Thomas P, AbdelRahman, Yasser M, Rose, Lorne A
• Format: Article
• Language: English
• Subjects: Amino acids; Bacteria; Cellular biology; Gene expression; Genomics; Protein synthesis
• ISSN: 0950-382X; 1365-2958

The developmentally regulated intracellular pathogen Chlamydia pneumoniae is a natural tryptophan auxotroph. These organisms survive tryptophan starvation induced by host cell activation with IFNγ by blocking maturation to the infectious form. In most bacteria, the stringent response is induced during amino acid starvation to promote survival. However, the response of obligate intracellular pathogens, which are predicted to lack stringent responses to amino acid starvation, is poorly characterized. Chlamydial transcription and translation were analyzed during IFNγ-mediated tryptophan starvation using genomic normalization methods, and the data revealed the novel findings that: (i) global chlamydial transcription was upregulated; and (ii) protein synthesis was dramatically reduced. These results indicate a dysregulation of developmental gene expression and an uncoupling of transcription from translation. These observations represent an alternative survival strategy for host-adapted obligate intracellular bacterial pathogens that have lost the genes for stringent control during reductive evolution. [PUBLICATION ABSTRACT]