eLife assessment
Sulphur atoms derived from cysteine are thought to play significant roles in maintaining redox homeostasis in Mycobacterium tuberculosis, which encounters stresses associated with immune cell interactions. In this valuable manuscript, the authors provide solid evidence that the genes encoding cysteine biosynthetic enzymes (cysM and cysK2) are required to maintain full viability of M. tuberculosis under in vitro stress conditions, macrophage infections, and within the lung tissues of mice. The manuscript presents transcriptomic and metabolomic evidence to support the hypothesis that CysM and CysK2 play distinct roles in maintaining cysteine-derived metabolite pools under stress conditions. The work will be of interest to microbiologists in general.