Research article

Chlamydia trachomatis responds to heat shock, penicillin induced persistence, and IFN-gamma persistence by altering levels of the extracytoplasmic stress response protease HtrA

Wilhelmina M Huston¹ , Christina Theodoropoulos² , Sarah A Mathews¹ and Peter Timms¹

¹  Institute of Health and Biomedical Innovation, 60 Musk Ave, Queensland University of Technology, Kelvin Grove, QLD, 4059, Australia

²  Analytical and Electron Microscopy Facility, Queensland University of Technology, Brisbane, QLD, 4001, Australia

author email corresponding author email

BMC Microbiology 2008, 8:190doi:10.1186/1471-2180-8-190

Published:	6 November 2008

Abstract

Background

Chlamydia trachomatis, an obligate intracellular human pathogen, is the most prevalent bacterial sexually transmitted infection worldwide and a leading cause of preventable blindness. HtrA is a virulence and stress response periplasmic serine protease and molecular chaperone found in many bacteria. Recombinant purified C. trachomatis HtrA has been previously shown to have both activities. This investigation examined the physiological role of Chlamydia trachomatis HtrA.

Results

The Chlamydia trachomatis htrA gene complemented the lethal high temperature phenotype of Escherichia coli htrA^- (>42°C). HtrA levels were detected to increase by western blot and immunofluorescence during Chlamydia heat shock experiments. Confocal laser scanning microscopy revealed a likely periplasmic localisation of HtrA. During penicillin induced persistence of Chlamydia trachomatis, HtrA levels (as a ratio of LPS) were initially less than control acute cultures (20 h post infection) but increased to more than acute cultures at 44 h post infection. This was unlike IFN-γ persistence where lower levels of HtrA were observed, suggesting Chlamydia trachomatis IFN-γ persistence does not involve a broad stress response.

Conclusion

The heterologous heat shock protection for Escherichia coli, and increased HtrA during cell wall disruption via penicillin and heat shock, indicates an important role for HtrA during high protein stress conditions for Chlamydia trachomatis.