Glucose 6-phosphate (G6P) is a metabolic intermediate with many possible cellular fates. In mycobacteria, G6P is a substrate for an enzyme, F 420 -dependent glucose-6-phosphate dehydrogenase (Fgd), found in few bacterial genera. Intracellular G6P levels in six Mycobacterium sp. were remarkably higher (ϳ17-130-fold) than Escherichia coli and Bacillus megaterium. The high G6P level in Mycobacterium smegmatis may result from 10 -25-fold higher activity of the gluconeogenic enzyme fructose-1,6-bisphosphatase when grown on glucose, glycerol, or acetate compared with B. megaterium and E. coli. In M. smegmatis this coincided with up-regulation of the first gluconeogenic enzyme, phosphoenolpyruvate carboxykinase, when acetate was the carbon source, suggesting a cellular program for maintaining high G6P levels. G6P was depleted in cells under oxidative stress induced by redox cycling agents plumbagin and menadione, whereas an fgd mutant of M. smegmatis used G6P less well under such conditions. The fgd mutant was more sensitive to these agents and, in contrast to wild type, was defective in its ability to reduce extracellular plumbagin and menadione. These data suggest that intracellular G6P in mycobacteria serves as a source of reducing power and, with the mycobacteriaspecific Fgd-F 420 system, plays a protective role against oxidative stress.

A definitive diagnosis of M. bovis infection in animals depends on the isolation of the organism, as the optimum condition for the primary isolation of M. bovis infection has not been determined. In this study a total number of 2550 cattle from different governorates in Egypt were tested by Single Intradermal Cervical (SID) tuberculin skin test. Positive reacted cattle (no= 42, 1.6%) were slaughtered and suspected lesions were collected, these samples were decontaminated by using three different methods, which were 0.75 % Hexadecyl Pyridinium Chloride (HPC), 5% oxalic acid and 6 % sulphuric acid. Isolation of mycobacteria from 42 samples by using these decontaminated methods were of 34 (80.9 %), 30 (71.4 %) and 28 (66.6 %), respectively. So it could be concluded that using HPC method as decontaminated agent revealed high rate of isolation of mycobacteria with less contamination (7.1 %) than the other two methods.