Lipoprotein processing is essential for resistance of Mycobacterium tuberculosis to malachite green

Niaz Banaei, Eleanor Z. Kincaid, S. Y.Grace Lin, Edward Desmond, William R. Jacobs, Joel D. Ernst

Research output: Contribution to journalArticlepeer-review

23 Scopus citations


Malachite green, a synthetic antimicrobial dye, has been used for over 50 years in mycobacterial culture medium to inhibit the growth of contaminants. The molecular basis of mycobacterial resistance to malachite green is unknown, although the presence of malachite green-reducing enzymes in the cell envelope has been suggested. The objective of this study was to investigate the role of lipoproteins in resistance of Mycobacterium tuberculosis to malachite green. The replication of an M. tuberculosis lipoprotein signal peptidase II (lspA) mutant (ΔlspA::lspAmut) on Middlebrook agar with and without 1 mg/liter malachite green was investigated. The lspA mutant was also compared with wild-type M. tuberculosis in the decolorization rate of malachite green and sensitivity to sodium dodecyl sulfate (SDS) detergent and first-line antituberculosis drugs. The lspA mutant has a 104-fold reduction in CFU-forming efficiency on Middlebrook agar with malachite green. Malachite green is decolorized faster in the presence of the lspA mutant than wild-type bacteria. The lspA mutant is hypersensitive to SDS detergent and shows increased sensitivity to first-line antituberculosis drugs. In summary, lipoprotein processing by LspA is essential for resistance of M. tuberculosis to malachite green. A cell wall permeability defect is likely responsible for the hypersensitivity of lspA mutant to malachite green.

Original languageEnglish (US)
Pages (from-to)3799-3802
Number of pages4
JournalAntimicrobial agents and chemotherapy
Issue number9
StatePublished - 2009

ASJC Scopus subject areas

  • Pharmacology
  • Pharmacology (medical)
  • Infectious Diseases


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