# Comparative transcriptomics reveals genes commonly induced by distinct stressors in Chlamydia

## TL;DR

The study compares how Chlamydia bacteria change their gene activity in response to different stress conditions, revealing shared and unique patterns.

## Contribution

The study identifies stressor-specific and shared transcriptomic responses in Chlamydia, highlighting potential vulnerabilities.

## Key findings

- Transcriptomic overlap is reduced when heat shock is included with chronic stress conditions.
- Tryptophan and iron starvation show closer transcriptomic similarity than with interferon-γ treatment.
- Interferon-γ induces a distinct but partially overlapping transcriptome, suggesting additional host mechanisms.

## Abstract

Chlamydia trachomatis is a leading cause of urogenital infections that can result in serious long-term complications. This obligate intracellular bacterium undergoes a biphasic developmental cycle alternating between the infectious elementary body and the replicative reticulate body and can enter a persistent state in response to adverse environmental conditions. Although transcriptomic reprogramming is central to chlamydial stress adaptation and persistence, how responses differ across biologically distinct stressors remains incompletely defined. Here, we performed a comparative reanalysis of five published, high-quality C. trachomatis RNA-Seq data sets generated under prolonged interferon-γ treatment, tryptophan starvation, iron starvation, penicillin exposure, or acute heat shock. Global transcriptomic analyses reveal stress-specific reprogramming and a clear separation between the transcriptome induced by heat shock and those induced by chronic stresses. Transcriptomic overlap observed among chronic stress conditions is substantially reduced when the heat shock transcriptome is included, indicating that shared transcriptional features are stressor-dependent. Consistent with prior findings, tryptophan starvation and iron starvation exhibit particularly close transcriptomic similarity, likely reflecting regulatory cross-talk mediated by the iron-dependent transcriptional repressor YtgR. Notably, this similarity exceeds that observed between tryptophan starvation and interferon-γ treatment, despite the well-established role of interferon-γ in inducing host-mediated tryptophan depletion. In contrast, interferon-γ induces a distinct but partially overlapping transcriptome, likely reflecting activation of additional host-mediated antimicrobial mechanisms beyond tryptophan deprivation. Together, these findings demonstrate that adaptation to different biological stressors in C. trachomatis is driven by distinct transcriptomic reprogramming, while consistently involving a subset of functions that may represent points of vulnerability for disrupting chlamydial persistence.