Abstract

Nearly one-third of the world's population is latently infected with Mycobacterium tuberculosis (M. tb), which represents a huge disease reservoir for reactivation and a major obstacle for effective control of tuberculosis. During latent infection, M. tb is thought to enter nonreplicative dormant states by virtue of its response to hypoxia and nutrient-deprived conditions. Knowledge of the genetic programs used to facilitate entry into and exit from the nonreplicative dormant states remains incomplete. In this study, we examined the transcriptional changes of Mycobacterium marinum (M. marinum), a pathogenic mycobacterial species closely related to M. tb, at different stages of resuscitation from hypoxia-induced dormancy. RNA-seq analyses were performed on M. marinum cultures recovered at multiple time points after resuscitation. Differentially expressed genes (DEGs) at each time period were identified and analyzed. Co-expression networks of transcription factors and DEGs in each period were constructed. In addition, we performed a weighted gene co-expression network analysis (WGCNA) on all genes and obtained 12 distinct gene modules. Collectively, these data provided valuable insight into the transcriptome changes of M. marinum upon resuscitation as well as gene module function of the bacteria during active metabolism and growth.

Highlights

  • Mycobacterium tuberculosis (M. tb), the causative agent of tuberculosis (TB), is the leading cause of death due to an infectious disease globally, with an estimated 10 million new cases and 1.3 million deaths in 2017

  • We examined the transcriptional changes of Mycobacterium marinum (M. marinum) at different stages of resuscitation from hypoxia-induced dormancy

  • To analyze transcriptome changes of M. marinum, we focused on genes with RPKM ≥ 10 and compared samples from adjacent intervals: between 0.5 and 0 hr, 4 and 0.5 hr, 12 and 4 hr, 24 and 12 hr, as well as 48 and 24 hr

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Summary

INTRODUCTION

Mycobacterium tuberculosis (M. tb), the causative agent of tuberculosis (TB), is the leading cause of death due to an infectious disease globally, with an estimated 10 million new cases and 1.3 million deaths in 2017. A second set of 230 genes, induced by longer hypoxia exposure (7 days), was identified (Rustad et al, 2008) These genes, collectively known as the enduring hypoxic response (EHR), were DosR-independent genes (Rustad et al, 2008). A few recent studies have used reaeration of hypoxic cultures for in vitro modeling of reactivation or resuscitation (Veatch and Kaushal, 2018). Several regulatory proteins, such as transcription factor ClgR and sigma factors SigH and SigE, were found to play a role in M. tb resuscitation from hypoxia (Mcgillivray et al, 2015; Iona et al, 2016; Veatch et al, 2016). Findings from the current study of M. marinum may be applicable to M. tb

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