Horizontal Gene Transfer (HGT) events, initially thought to be rare in Mycobacterium tuberculosis, have recentlybeen shown to be involved in the acquisition of virulence operons in M. tuberculosis. We have developed a newpartitioning framework based HGT prediction algorithm, called Grid3M, and applied the same for the prediction ofHGTs in Mycobacteria. Validation and testing using simulated and real microbial genomes indicated better performanceof Grid3M as compared with other widely used HGT prediction methods. Specific analysis of the genesbelonging to dormancy/reactivation regulons across 14 mycobacterial genomes indicated that horizontal acquisition isspecifically restricted to important accessory proteins. The results also revealed Burkholderia species to be a probablesource of HGT genes belonging to these regulons. The current study provides a basis for similar analyses investigatingthe functional/evolutionary aspects of HGT genes in other pathogens. A database of Grid3M predicted HGTs incompletely sequenced genomes is available at https://metagenomics.atc.tcs.com/Grid3M/.