Role of P27-P55 operon from Mycobacterium tuberculosis in the resistance to toxic compounds

Abstract

BackgroundThe P27-P55 (lprG-Rv1410c) operon is crucial for the survival of Mycobacterium tuberculosis, the causative agent of human tuberculosis, during infection in mice. P55 encodes an efflux pump that has been shown to provide Mycobacterium smegmatis and Mycobacterium bovis BCG with resistance to several drugs, while P27 encodes a mannosylated glycoprotein previously described as an antigen that modulates the immune response against mycobacteria. The objective of this study was to determine the individual contribution of the proteins encoded in the P27-P55 operon to the resistance to toxic compounds and to the cell wall integrity of M. tuberculosis.MethodIn order to test the susceptibility of a mutant of M. tuberculosis H37Rv in the P27-P55 operon to malachite green, sodium dodecyl sulfate, ethidium bromide, and first-line antituberculosis drugs, this strain together with the wild type strain and a set of complemented strains were cultivated in the presence and in the absence of these drugs. In addition, the malachite green decolorization rate of each strain was obtained from decolorization curves of malachite green in PBS containing bacterial suspensions.ResultsThe mutant strain decolorized malachite green faster than the wild type strain and was hypersensitive to both malachite green and ethidium bromide, and more susceptible to the first-line antituberculosis drugs: isoniazid and ethambutol. The pump inhibitor reserpine reversed M. tuberculosis resistance to ethidium bromide. These results suggest that P27-P55 functions through an efflux-pump like mechanism. In addition, deletion of the P27-P55 operon made M. tuberculosis susceptible to sodium dodecyl sulfate, suggesting that the lack of both proteins causes alterations in the cell wall permeability of the bacterium. Importantly, both P27 and P55 are required to restore the wild type phenotypes in the mutant.ConclusionsThe results clearly indicate that P27 and P55 are functionally connected in processes that involve the preservation of the cell wall and the transport of toxic compounds away from the cells.

Malachite Green Interferes with Postantibiotic Recovery of Mycobacteria

“…Second, increased permeability of cells exposed to cell wall targeting antibiotics could facilitate the access of malachite green to its molecular target(s). Consistent with this interpretation, two recent reports demonstrated that mutant strains of mycobacteria with increased cell wall permeability are hypersensitive to malachite green (3,4). Third, antibiotic-mediated killing has been linked to the production of reactive oxygen species (ROS) in Gram-negative and Gram-positive bacteria (7), and malachite green has been shown to trigger ROS production via an unknown mechanism (18).…”

In Search of El Dorado: Current Trends and Strategies in the Development of Novel Anti-Tubercular Drugs

“…These results were very recently confirmed by Bianco et al. who demonstrated that the LprG-P55 operon is required for proper cell wall assembly (Bianco et al, 2011). Intriguingly, only one gene (mmr) belonging to the SMR (Small Multidrug Resistance Family) family and related to drug efflux (in this case Erythromicin) has been located in the M. tuberculosis chromosome (De Rossi et al, 1998).…”

Contribution of Efflux to the Emergence of Isoniazid and Multidrug Resistance in Mycobacterium tuberculosis

“…Nevertheless, even considering the more stringent value of four, a clear and general ability to trigger efflux pump genes overexpression in response to isoniazid presence was observed along the exposure processes, for all strains. The genes for which a more consistent isoniazid-mediated response was observed, were the genes involved in the transport and synthesis of mycolic acids, mmpL7 and efpA respectively [41], [42], and p55 , considered to be involved in isoniazid transport [17], [20], [38], [43], [44]. Again, our study complements other earlier findings [15], [34], [36], who suggested the involvement of these genes in the resistance to isoniazid, by providing experimental data showing that susceptible reference strain and clinical strains use these pumps as an immediate response to the presence of isoniazid concentrations that are considered to be inhibitory.…”