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Updated: Jun 19, 2026
A Microscopic Phenotypic Assay for the Quantification of Intracellular Mycobacteria Adapted for High-throughput/High-content Screening
Published on: January 17, 2014
Disruption of an M. tuberculosis membrane protein causes a magnesium-dependent cell division defect and failure to
Nichole Goodsmith1, Xinzheng V Guo1, Omar H Vandal1
1Department of Microbiology and Immunology, Weill Cornell Medical College, New York, New York, United States of America.
Abstract:
The identification of Mycobacterium tuberculosis genes necessary for persistence in vivo provides insight into bacterial biology as well as host defense strategies. We show that disruption of M. tuberculosis membrane protein PerM (Rv0955) resulted in an IFN-γ-dependent persistence defect in chronic mouse infection despite the mutant's near normal growth during acute infection. The perM mutant required increased magnesium for replication and survival; incubation in low magnesium media resulted in cell elongation and lysis. Transcriptome analysis of the perM mutant grown in reduced magnesium revealed upregulation of cell division and cell wall biosynthesis genes, and live cell imaging showed PerM accumulation at the division septa in M. smegmatis. The mutant was acutely sensitive to β-lactam antibiotics, including specific inhibitors of cell division-associated peptidoglycan transpeptidase FtsI. Together, these data implicate PerM as a novel player in mycobacterial cell division and pathogenesis, and are consistent with the hypothesis that immune activation deprives M. tuberculosis of magnesium.
Insights
Disrupting the Mycobacterium tuberculosis PerM protein impairs bacterial persistence during chronic infection. This membrane protein is crucial for cell division and survival, especially under low magnesium conditions linked to host immune responses.
Area of Science:
- Microbiology
- Immunology
- Pathogenesis
Background:
- Mycobacterium tuberculosis (M.tb) persistence is key to chronic infection.
- Understanding bacterial genes involved in persistence offers insights into host defense.
Purpose of the Study:
- To identify M.tb genes essential for in vivo persistence.
- To investigate the role of membrane protein PerM in M.tb pathogenesis and survival.
Main Methods:
- Gene disruption of M.tb membrane protein PerM (Rv0955).
- In vivo chronic mouse infection model assessing IFN-γ dependence.
- In vitro studies on magnesium requirements, cell morphology, and antibiotic sensitivity.
- Transcriptome analysis under reduced magnesium conditions.
- Live cell imaging in M. smegmatis to observe PerM localization.
Main Results:
- PerM disruption caused an IFN-γ-dependent persistence defect in chronic infection.
- The perM mutant exhibited increased magnesium dependency, with low magnesium leading to cell elongation and lysis.
- Transcriptome analysis revealed altered cell division and cell wall biosynthesis genes in the mutant.
- PerM was observed to accumulate at division septa.
- The mutant showed hypersensitivity to β-lactam antibiotics targeting FtsI.
Conclusions:
- PerM is implicated as a novel factor in mycobacterial cell division and pathogenesis.
- These findings support the hypothesis that host immune activation (via IFN-γ) may reduce magnesium availability, impacting M.tb survival.
