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Carotenoids are complex lipids that are known for acting against photodynamic injury and free radicals. We demonstrate here that [[sigma].sup.F] is required for carotenoid pigment production in Mycobacterium smegmatis. We further show that a sigF mutant exhibits a transformation efficiency [10.sup.4]-fold higher than that of the parental strain, suggesting that [[sigma].sup.F] regulates the production of components affecting cell wall permeability. In addition, a sigF mutant showed an increased sensitivity to hydrogen peroxide. An in silico search of the M. smegmatis genome identified a number of SigF consensus sites, including sites upstream of the carotenoid synthesis locus, which explains its SigF regulation.

The cell envelope of mycobacteria is a complex structure that plays an important role in the interactions of the cell with its environment and in the protection against the antimicrobial activity of the immune system. Glycopeptidolipids (GPLs) are species- or type species-specific glycolipids that are present at the surface of a number of mycobacteria and that are characterized by a high variability in glycosylation patterns. These GPLs possess various biological activities that depend mostly on the sugars capping the core molecule. In Mycobacterium smegmatis, the GPL core can be substituted by either two or three deoxyhexoses. In this study, we show that Gtf3 is a glycosyltransferase responsible for the synthesis of the triglycosylated GPLs. Biochemical analysis of these molecules, with a combination of mass spectrometry and chemical degradation methods, has shown that they contain three deoxyhexose moieties. The presence of the triglycosylated GPLs is associated with cell surface modifications that lead to a decrease in sliding motility as well as a modification in cellular aggregation and colony appearance on Congo red. Phylogenetic analysis indicated that Gtf3 is a member of a yet-uncharacterized glycosyltransferase family conserved among the mycobacteria.

The Bacillus subtilis structural gene sacB encodes levansucrase, a high-molecular-weight protein located in the periplasm. Expression of sacB in the presence of 10% sucrose is lethal to Mycobacterium smegmatis and Mycobacterium bovis BCG. In this study, a mycobacterium conjugative shuttle vector carrying the sacB gene was constructed and inserted into mycobacterial cells. Results revealed repression of growth of transformants on sucrose-supplemented medium, suggesting that sacB can be used as a counterselectable marker in mycobacteria.

Phosphorylation of an alternate residue by FixL of Rhizobium meliloti increases transcriptional process of mutant FixJD54N protein. FixJ functions as a transcriptional activator whereas FixL cats as a homoprotein kinase. FixJD54N's phosphorylation site is changed to asparagine from aspartate 54 and involves the function of FixL and ATP elements. Oxygen signal transduction is done by Asp-54 of FixJ.

Two proteins, FixL and FixJ, belonging to the two-component family of regulatory proteins, are essential for oxygen-regulated in vitro transcription of two vital regulatory genes nifA and fixK. FixJ is a transcriptional activator which functions in combination with the RNA polymerase sigma 70 holoenzyme. FixJ transcriptional activity is augmented by the addition of FixL122 to the transcription assay.

The cell envelope of mycobacteria is a complex structure that plays an important role in the interactions of the cell with its environment and in the protection against the antimicrobial activity of the immune system. Glycopeptidolipids (GPLs) are species- or type species-specific glycolipids that are present at the surface of a number of mycobacteria and that are characterized by a high variability in glycosylation patterns. These GPLs possess various biological activities that depend mostly on the sugars capping the core molecule. In Mycobacterium smegmatis, the GPL core can be substituted by either two or three deoxyhexoses. In this study, we show that Gtf3 is a glycosyltransferase responsible for the synthesis of the triglycosylated GPLs. Biochemical analysis of these molecules, with a combination of mass spectrometry and chemical degradation methods, has shown that they contain three deoxyhexose moieties. The presence of the triglycosylated GPLs is associated with cell surface modifications that lead to a decrease in sliding motility as well as a modification in cellular aggregation and colony appearance on Congo red. Phylogenetic analysis indicated that Gtf3 is a member of a yet-uncharacterized glycosyltransferase family conserved among the mycobacteria. [ABSTRACT FROM AUTHOR]