Project description:To determine the role that GrgA plays in chlamydial physiology, we constructed a Chlamydia trachomatis mutant that we term L/cgad-peig, in which the chromosomal grgA (ctl0766 or ct504) has been disrupted by Targetron mutagenesis, and the plasmid carries an inducible grgA under the control of anhydrotetracycline (ATC). RNA-Seq analysis was performed for L2/cgad-peig grown with and without ATC.
Project description:The obligate intracellular developmental cycle of Chlamydia trachomatis presents significant challenges in defining its proteome. In this study we have applied quantitative proteomics to both the intracellular reticulate body (RB) and the extracellular elementary body (EB) from C. trachomatis. We used C. trachomatis L2 which is a model chlamydial isolate for such a study since it has a high infectivity: particle ratio and there is an excellent quality genome sequence. EBs and RBs (>99% pure) were quantified by chromosomal and plasmid copy number using PCR to determine the concentrations of chlamydial proteins per bacterial cell. RBs harvested at 15h post infection (PI) were purified by three successive rounds of gradient centrifugation. This is the earliest possible time to obtain purified RBs, free from host cell components in quantity, within the constraints of the technology, EBs were purified at 48h PI. We then used two-dimensional reverse phase UPLC to fractionate RB or EB peptides before mass spectroscopic analysis, providing absolute amount estimates of chlamydial proteins.
Project description:C. trachomatis possess a cryptic 7.5 kb plasmid of unknown function. Here we describe a comprehensive molecular and biological characterization of the naturally occurring plasmidless human Chlamydia trachomatis strain L2 (25667R). We found that despite minimal chromosomal polymorphisms the LGV L2 (25667R) strain was indistinguishable from the L2 (434) plasmid positive strain in its in vitro infectivity characteristics such as growth kinetics, plaquing efficiency, and plaque size. The primary in vitro phenotypic differences between L2 (434) and L2 (25667R) were the accumulation of glycogen granules in the inclusion matrix and the lack of the typical intra-inclusion Brownian-like movement characteristic of C. trachomatis strains. Conversely, we observed a marked difference between the two strains in their ability to colonize and infect the female mouse genital tract. The ID50 of the L2 (25667R) plasmidless strain was 500 fold greater (1.XX x 10X IFU) than the L2 (434) plasmid bearing strain (1. XX x 10X IFU). Transcriptome analysis of the two strains clearly demonstrated a decrease in transcript levels of a subset of chromosomal genes for the L2 (25667R) strain. Among those genes was glgA which encodes for glycogen synthase; a finding consistent with the failure of the L2 (25667R) strain to accumulate glycogen granules. Collectively, these findings support an important role for the plasmid in in vivo infectivity and suggest that this virulence characteristic might be controlled by the plasmids ability to regulate the expression of specific chromosomal genes. These results also support an important role for the plasmid in the pathogenesis of human infection and disease. Keywords: strain comparison C. trachomatis strain L2-25667R compared to strain L2-434
