Regulation of Lipid Biosynthesis, Sliding Motility, and Biofilm Formation by a Membrane-Anchored Nucleoid-Associated Protein of Mycobacterium tuberculosis

Abstract

bBacteria use a number of small basic proteins for organization and compaction of their genomes. By their interaction with DNA, these nucleoid-associated proteins (NAPs) also influence gene expression. Rv3852, a NAP of Mycobacterium tuberculosis, is conserved among the pathogenic and slow-growing species of mycobacteria. Here, we show that the protein predominantly localizes in the cell membrane and that the carboxy-terminal region with the propensity to form a transmembrane helix is necessary for its membrane localization. The protein is involved in genome organization, and its ectopic expression in Mycobacterium smegmatis resulted in altered nucleoid morphology, defects in biofilm formation, sliding motility, and change in apolar lipid profile. We demonstrate its crucial role in regulating the expression of KasA, KasB, and GroEL1 proteins, which are in turn involved in controlling the surface phenotypes in mycobacteria.

Rv3852 (H-NS) of Mycobacterium tuberculosis Is Not Involved in Nucleoid Compaction and Virulence Regulation

“…Overall, our experimental results rule out a role for Rv3852 as a global transcriptional regulator. The discrepancy between our findings and those of Ghosh et al (21) could be ascribed to the ectopic expression of M. tuberculosis H-NS in M. smegmatis, a species that has no ortholog of rv3852 in its genome (17). The expression system employed by Ghosh and coworkers may have altered the regulatory network in the bacterium, thus generating an aberrant phenotype.…”

“…3), contrary to the findings of Ghosh and colleagues upon overexpression of M. tuberculosis H-NS in M. smegmatis (21). Moreover, unlike Ghosh et al (21), who reported deregulation of the fatty acid biosynthetic genes kasA and kasB and of the major chaperone gene groEL1, we observed no change in expression of these genes when comparing the global transcriptome of the wild-type strain H37Rv to that of the Δrv3852 mutant by RNA-seq. Besides, we found only two genes involved in fatty acid metabolism (fadD11 and lipQ) and three coding for probable transcriptional regulators (rv0232, mce1R, and rv2989) that were slightly deregulated in expression.…”

“…It was reported that expression of kasA and groEL1 was reduced fourfold upon ectopic expression of M. tuberculosis Rv3852 in M. smegmatis (21). We did not observe the same deregulation in our experiments, where kasA, kasB, the intergenic region between the two genes and groEL1 were expressed at similar levels in the mutant and wild-type strains (Data Set S1).…”

“…Ectopic expression of M. tuberculosis rv3852 in M. smegmatis led to a less-compacted nucleoid, altered biofilm formation, and decreased sliding motility (21). Unusually for a NAP, the C-terminal domain of Rv3852 was identified as a transmembrane helix, suggesting a role in anchoring DNA to the membrane.…”

“…Unusually for a NAP, the C-terminal domain of Rv3852 was identified as a transmembrane helix, suggesting a role in anchoring DNA to the membrane. RNA profiling showed that expression of groEL1, a heat shock chaperone, and kasA, involved in fatty acid biosynthesis, are downregulated upon expression of rv3852 in M. smegmatis (21).…”