DNA-bridging protein that has both architectural and regulatory roles (PubMed:18187505). Influences the organization of chromatin and gene expression by binding non-specifically to DNA, with a preference for AT-rich sequences, and bridging distant DNA segments (PubMed:20133735). Binds in the minor groove of AT-rich DNA (PubMed:21673140). Represses expression of multiple genes involved in a broad range of cellular processes, including major virulence factors or antibiotic-induced genes, such as iniBAC or efpA (PubMed:17590082), and genes important for adaptation of changing O(2) levels (PubMed:24895305). May also activate expression of some gene (PubMed:24895305). May coordinate global gene regulation and virulence (PubMed:20133735). Also protects mycobacteria against reactive oxygen intermediates during macrophage infection by acting as a physical barrier to DNA degradation (PubMed:19237572); the physical protection has been questioned (PubMed:24895305). A strain overexpressing this protein consumes O(2) more slowly than wild-type (PubMed:24895305). Homodimer. May form higher oligomers via protease-activation. The C-terminal domain binds DNA and the N-terminal domain is involved in dimerization. Both domains are essential for normal function. The three N-terminal residues may be cleaved by proteases in response to external stress. This cleavage may be required for oligomerization, which leads to chromosome compaction and protection. No visible effect on nucleoid structure during anaerobic growth by whole cell staining. Sensitive to atmospheric O(2) levels, at 2% O(2) no difference in growth up to 14 days; required for adaptation to anaerobiosis, at 21 days nearly 1000-fold decrease in survival under anaerobic conditions. Consumes O(2) more rapidly. Has a significant lag in recovery from 7 or 14 days anaerobic growth. Decreased virulence in lungs of BALB/c mice; no visible lung disease at any time point. Increased sensitivity to reactive nitrogen species, not more sensitive to H(2)O(2) or mitomycin (PubMed:24895305). Belongs to the Lsr2 family.