The H2O2 inherently released by the mycobacterial minor subpopulation enhances the survival of the major kin subpopulation against rifampicin

• Authors: Rashmi Ravindran Nair, Indian Institute of Science; Deepti Sharan, Indian Institute of Science; Vijay Srinivasan, Indian Institute of Science; Nagaraja Mukkayyan, Indian Institute of Science; Kishor Jakkala, Indian Institute of Science; Parthasarathi Ajitkumar, Indian Institute of Science
• Journal Title: Current Research in Microbial Sciences
• Volume: Volume 3
• Publisher: Elsevier | 2022-06-18
• Type of Work: Article | Final Publisher PDF
• Publisher DOI: http://doi.org/10.1016/j.crmicr.2022.100148
• Subjects: Biology, Microbiology
• Keywords: Mycobacteria; Bacterial subpopulations; Rifampicin; Isoniazid; H2O2; Antibiotic stress; Oxidative stress; Survival

Abstract

Exposure to antibiotics most often generates oxidative stress in bacteria. Oxidative stress survival mechanisms would facilitate the evolution of antibiotic resistance. As part of an effort to understand oxidative stress survival mechanisms in mycobacteria, here we show that the minor subpopulation (SCs; short-sized cells constituting 10% of the population) of Mycobacterium smegmatis significantly increased the survival of its major kin subpopulation (NCs; normal/long-sized cells constituting 90% of the population) in the mid-log-phase (MLP) cultures against the oxidative stress induced by rifampicin and exogenously added H2O2 (positive control). We had earlier shown that the SCs in the MLP cultures inherently and naturally release significantly high levels of H2O2 into the medium. Addition of the SCs’ culture supernatant, unlike the supernatant of the dimethylthiourea (H2O2 scavenger) exposed SCs, enhanced the survival of NCs. It indicated that NCs’ survival required the H2O2 present in the SCs’ supernatant. This H2O2 transcriptionally induced high levels of catalase-peroxidase (KatG) in the NCs. The naturally high KatG levels in the NCs significantly neutralised the endogenous H2O2 formed upon exposure to rifampicin or H2O2, thereby enhancing the survival of NCs against oxidative stress. The absence of such enhanced survival in the furA-katG and katG knockout (KO) mutants of NCs in the presence of wild-type SCs, confirmed the requirement of the H2O2 present in the SCs’ supernatant and NCs’ KatG for enhanced oxidative stress survival. The presence of SCs:NCs at 1:9 in the pulmonary tuberculosis patients’ sputum alludes to the clinical significance of the finding.