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The metabolic activity of Mycobacterium tuberculosis , assessed by use of a novel inducible GFP expression system, correlates with its capacity to inhibit phagosomal maturation and acidification in human macrophages
Author(s) -
Lee BaiYu,
Clemens Daniel L.,
Horwitz Marcus A.
Publication year - 2008
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2008.06214.x
Subject(s) - phagosome , biology , mycobacterium tuberculosis , green fluorescent protein , microbiology and biotechnology , lac operon , bacteria , intracellular , mycobacterium , intracellular parasite , tuberculosis , recombinant dna , biochemistry , phagocytosis , gene , medicine , genetics , pathology
Summary Mycobacterium tuberculosis generally reside in phagosomes within human macrophages that resist maturation and acidification, but exhibit significant heterogeneity. In this study we have constructed an IPTG‐inducible GFP expression system in M. tuberculosis to assess the relationship between the metabolic status of M. tuberculosis and the degree of phagosomal maturation. Using these recombinant bacteria, we have found that, in human macrophages, M. tuberculosis that respond to IPTG with expression of GFP fluorescence, and hence are metabolically active, reside in non‐acidified phagosomes that have not fused with Texas red dextran pre‐labelled lysosomes. In contrast, M. tuberculosis that fail to express GFP in response to IPTG, and hence are metabolically inactive, reside within acidified phagosomes that have fused with Texas red dextran labelled lysosomes. These studies demonstrate that metabolic activity of M. tuberculosis correlates strongly with phagosomal maturation and that the inducible GFP expression system is useful for assessing metabolic activity of intracellular M. tuberculosis .