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Green fluorescent protein as a marker for gene expression and cell biology of mycobacterial interactions with macrophages
Author(s) -
Dhandayuthapani S.,
Via L.E.,
Thomas C.A.,
Horowitz P.M.,
Deretic D.,
Deretic V.
Publication year - 1995
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.1365-2958.1995.mmi_17050901.x
Subject(s) - biology , green fluorescent protein , mycobacterium bovis , mycobacterium smegmatis , cell sorting , aequorea victoria , promoter , microbiology and biotechnology , gene expression , expression vector , complementary dna , fusion protein , shuttle vector , fluorescence microscope , mycobacterium tuberculosis , gene , flow cytometry , recombinant dna , vector (molecular biology) , genetics , fluorescence , tuberculosis , medicine , physics , pathology , quantum mechanics
The green fluorescent protein (GFP) of the jellyfish Aequorea victoria offers certain advantages over other bioluminescence systems because no exogenously added substrate or co‐factors are necessary, and fluorescence can be elicited by irradiation with blue light without exposing the cells producing GFP to invasive treatments. A mycobacterial shuttle‐plasmid vector carrying gfp cDNA was constructed and used to generate transcriptional fusions with promoters of interest and to examine their expression in Mycobacterium smegmatis and Mycobacterium bovis BCG grown in macrophages or on laboratory media. The promoters studied were: (i) ahpC from Mycoosis and Mycobacterium leprae , a gene encoding alkyl hydroperoxide reductase which, along with the divergently transcribed regulator oxyR , are homologues of corresponding stress‐response systems in enteric bacteria and play a role in isoniazid sensitivity; (ii) mtrA , an M. tuberculosis response regulator belonging to the superfamily of bacterial two‐component signal‐transduction systems; (iii) hsp60 , a previously characterized heat‐shock gene from M. bovis ; and (iv) tbprc3 , a newly isolated promoter from M. tuberculosis . Expression of these promoters in mycobacteria was analysed using epifluorescence microscopy, laser scanning confocal microscopy, fluorescence spectroscopy, and flow cytometry. These approaches permitted assessment of fluorescence prior to and after macrophage infection, and analyses of promoter expression in individual mycobacteria and its distribution within populations of bacterial cells. Bacteria expressing GFP from a strong promoter could be separated by fluorescence‐activated cell sorting from cells harbouring the vector used to construct the fusion. In addition, the stable expression of mtrA‐gfp fusion in M. bovis BCG facilitated localization and isolation of phagocytic vesicles containing mycobacteria. The experiments presented here suggest that GFP will be a useful tool for analysis of mycobacterial gene expression and a convenient cell biology marker to study mycobacterial interactions with macrophages.