Chlamydia trachomatis ChxR is a transcriptional regulator of virulence factors that function in in vivo host-pathogen interactions

Pathog Dis. 2017 Apr 1;75(3):ftx035. doi: 10.1093/femspd/ftx035.


Chlamydia trachomatis is an obligate intracellular pathogen characterized by a unique biphasic developmental cycle that alternates between infectious and non-infectious organisms. Chlamydial ChxR is a transcriptional activator that has been implicated in the regulation of the development cycle. We used a reverse genetics approach to generate three chxR null mutants. All three mutants grew normally in cultured mammalian cells. Whole genome sequencing identified SNPs in other genes; however, none of the mutated genes were common to all three ChxR null mutants arguing against a genetic compensatory mechanism that would explain the non-essential in vitro growth phenotype. Comparative proteomics identified five proteins, CT005, CT214, CT565, CT694 and CT695, that were significantly downregulated in all ChxR null mutants. This group includes established inclusion membrane and type III secreted proteins. ChxR transcriptional regulation of these genes was confirmed by qRT-PCR. Importantly, while ChxR null mutants exhibited no growth deficiencies in in vitro, they did show significant differences in in vivo growth using a mouse genital tract model. Collectively, our findings demonstrated that ChxR is a transcriptional activator that regulates the expression of virulence genes whose functions are restricted to in vivo infection.

Keywords: Chlamydia; ChxR; in vivo infection; transcription.

Publication types

  • Research Support, N.I.H., Intramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alleles
  • Animals
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Cell Line
  • Chlamydia Infections / genetics*
  • Chlamydia Infections / microbiology*
  • Chlamydia trachomatis / genetics
  • Chlamydia trachomatis / growth & development
  • Chlamydia trachomatis / metabolism*
  • Disease Models, Animal
  • Female
  • Gene Expression
  • Gene Expression Regulation
  • Genome, Bacterial
  • Host-Pathogen Interactions*
  • Humans
  • Mice
  • Mutation
  • Sequence Analysis, DNA
  • Transcription Factors / genetics
  • Transcription Factors / metabolism*
  • Virulence Factors / genetics
  • Virulence Factors / metabolism


  • Bacterial Proteins
  • Transcription Factors
  • Virulence Factors