Variable transcriptional adaptation between the laboratory (H37Rv) and clinical strains (S7 and S10) of Mycobacterium tuberculosis under hypoxia

- Variable gene expressions, under hypoxia, between standard laboratory strain (H37Rv) and clinical isolates (S7 and S10) of Mycobacterium tuberculosis
- Most prevalent south Indian clinical strains of Mycobacterium tuberculosis were used.
- Ten inversely related genes that were repressed under hypoxia in H37Rv, by microarray, were up-regulated in both clinical isolates.
- All the 10 genes were validated by quantitative real-time PCR (qRT-PCR).
- Highlights the need of using clinical isolated for in vitro experiments to minimize variations

Tuberculosis continues to be a major public health problem in many parts of the world, despite intensified efforts taken to control the disease. The remarkable success of M. tuberculosis as a pathogen is largely due to its ability to persist within the host for long periods. To develop the effective intervention strategies, understanding the biology of persistence is highly required. Accumulating evidences showed oxygen deprivation (hypoxia) as a potential stimulus for triggering the transition of M. tuberculosis to a non-replicating persistent state analogous to latency in vivo. To date, in vitro hypoxia experimental models used the laboratory adapted isolate H37Rv and very little is known about the behavior of clinical isolates that are involved during disease outbreaks. Hence, we compared the transcription profiles of H37Rv and two south Indian clinical isolates (S7 and S10) under hypoxia to find differences in gene expression pattern. The main objective of this current work is to find “differentially regulated genes” (genes that are down regulated in H37Rv but upregulated in both the clinical isolates) under hypoxia. Microarray results showed, a total of 502 genes were down regulated in H37Rv under hypoxia and 10 out of 502 genes were upregulated in both the clinical isolates. Thus, giving less importance to down regulated genes based on H37Rv model strain might exclude the true representative gene candidates in clinical isolates. Our study suggests the use of most prevalent clinical isolates for in vitro experimental model to minimize the variation in understanding the adaptation mechanisms of the strains.