A Member of an Ancient Family of Bacterial Amino Acids Transporters Contributes to Chlamydia Nutritional Virulence and Immune Evasion

Expression activation of over 70% of Chlamydia trachomatis genes during the first hour of infection

The obligate intracellular bacterium Chlamydia has a unique developmental cycle that alternates between two contrasting cell types. With a hardy envelope and highly condensed genome, the small elementary body (EB) maintains limited metabolic activities yet survives in extracellular environments and is infectious. After entering host cells, EBs differentiate into larger and proliferating reticulate bodies (RBs). Progeny EBs are derived from RBs in late developmental stages and eventually exit host cells. How expression of the chlamydial genome consisting of nearly 1,000 genes governs the chlamydial developmental cycle is unclear. A previous microarray study identified only 29 Chlamydia trachomatis immediate early genes, defined as genes with increased expression during the first hour postinoculation in cultured cells. In this study, we performed more sensitive RNA sequencing (RNA-Seq) analysis for C. trachomatis cultures with high multiplicities of infection. Remarkably, we observed well over 700 C. trachomatis genes that underwent 2- to 900-fold activation within 1 hour postinoculation. Quantitative reverse transcription real-time PCR analysis was further used to validate the activated expression of a large subset of the genes identified by RNA-Seq. Importantly, our results demonstrate that the immediate early transcriptome is over 20 times more extensive than previously realized. Gene ontology analysis indicates that the activated expression spans all functional categories. We conclude that over 70% of C. trachomatis genes are activated in EBs almost immediately upon entry into host cells, thus implicating their importance in initiating rapid differentiation into RBs and establishing an intracellular niche conducive with chlamydial development and growth.

Natural Clearance of Chlamydia trachomatis Infection Is Associated With Distinct Differences in Cervicovaginal Metabolites

BACKGROUND

Natural clearance of Chlamydia trachomatis in women occurs in the interval between screening and treatment. In vitro, interferon-γ (IFN-γ)-mediated tryptophan depletion results in C. trachomatis clearance, but whether this mechanism occurs in vivo remains unclear. We previously found that women who naturally cleared C. trachomatis had lower cervicovaginal levels of tryptophan and IFN-γ compared to women with persisting infection, suggesting IFN-γ-independent pathways may promote C. trachomatis clearance.

METHODS

Cervicovaginal lavages from 34 women who did (n = 17) or did not (n = 17) naturally clear C. trachomatis were subjected to untargeted high-performance liquid chromatography mass-spectrometry to identify metabolites and metabolic pathways associated with natural clearance.

RESULTS

In total, 375 positively charged metabolites and 149 negatively charged metabolites were annotated. Compared to women with persisting infection, C. trachomatis natural clearance was associated with increased levels of oligosaccharides trehalose, sucrose, melezitose, and maltotriose, and lower levels of indoline and various amino acids. Metabolites were associated with valine, leucine, and isoleucine biosynthesis pathways.

CONCLUSIONS

The cervicovaginal metabolome in women who did or did not naturally clear C. trachomatis is distinct. In women who cleared C. trachomatis, depletion of various amino acids, especially valine, leucine, and isoleucine, suggests that amino acids other than tryptophan impact C. trachomatis survival in vivo.