SGCG and infection: The nuo G gene encodes the NuoG subunit of the type I NADH (nicotinamide adenine dinucleotide)-dehydrogenase of Mtb. Deletion of this gene leads to elevated ROS levels and apoptosis following infection of primary macrophages [40].Similarly, deletion of the secA2 gene, which encodes a protein required for the secretion of superoxide dismutase A, results in enhanced ROS production and apoptosis.Superoxide dismutase A breaks down superoxide leading to diminished ROS generation, which is a mechanism that Mtb uses to prevent apoptosis [41].