Research Article: Chlamydia trachomatis and Chlamydia muridarum spectinomycin resistant vectors and a transcriptional fluorescent reporter to monitor conversion from replicative to infectious bacteria

Date Published: June 6, 2019

Publisher: Public Library of Science

Author(s): María Eugenia Cortina, Rachel J. Ende, R. Clayton Bishop, Charlie Bayne, Isabelle Derré, Agathe Subtil.


Chlamydia trachomatis infections are the leading cause of sexually transmitted infections of bacterial origin. Lower genital tract infections are often asymptomatic, and therefore left untreated, leading to ascending infections that have long-term consequences on female reproductive health. Human pathology can be recapitulated in mice with the mouse adapted strain C. muridarum. Eight years into the post-genetic era, significant advances to expand the Chlamydia genetic toolbox have been made to facilitate the study of this important human pathogen. However, the need for additional tools remains, especially for C. muridarum. Here, we describe a new set of spectinomycin resistant E. coli-Chlamydia shuttle vectors, for C. trachomatis and C. muridarum. These versatile vectors allow for expression and localization studies of Chlamydia effectors, such as Inc proteins, and will be instrumental for mutant complementation studies. In addition, we have exploited the differential expression of specific Chlamydia genes during the developmental cycle to engineer an omcA::gfp fluorescent transcriptional reporter. This novel tool allows for monitoring RB to EB conversion at the bacterial level. Spatiotemporal tracking of GFP expression within individual inclusions revealed that RB to EB conversion initiates in bacteria located at the edge of the inclusion and correlates with the time post initiation of bacterial replication and inclusion size. Comparison between primary and secondary inclusions potentially suggests that the environment in which the inclusions develop influences the timing of conversion. Altogether, the Chlamydia genetic tools described here will benefit the field, as we continue to investigate the molecular mechanisms underlying Chlamydia-host interaction and pathogenesis.

Partial Text

Chlamydia spp. are Gram-negative obligate intracellular bacterial pathogens that infect a wide range of hosts and are responsible for various diseases. Chlamydia trachomatis is the leading cause of sexually transmitted infections of bacterial origin and the most common cause of non-congenital blindness due to trachoma [1]. Infection with C. pneumoniae leads to community-acquired pneumonia [2]. C. felis, C. caviae, and C. suis are among Chlamydia species that infect animals [3]. Of interest to this study, the mouse-adapted strain C. muridarum is commonly used to model human female genital tract infections, because intravaginal C. muridarum infection in mice recapitulates the upper genital tract pathology observed with C. trachomatis infection in women [4].

Altogether, we present here a new set of genetic tools for C. trachomatis and C. muridarum that will be instrumental as the field continues to harness the power of genetics to study this important pathogen.