@article { ISI:000240369800005, title = {Identification of a respiratory-type nitrate reductase and its role for survival of mycobacterium smegmatis in wayne model}, journal = {Microbial Pathogenesis}, volume = {41}, number = {2-3}, year = {2006}, month = {AUG}, pages = {90-95}, publisher = {ACADEMIC PRESS LTD ELSEVIER SCIENCE LTD}, type = {Article}, address = {24-28 OVAL RD, LONDON NW1 7DX, ENGLAND}, abstract = {

Nitrate reductase (NR) is found to be expressed in certain mycobacterium sp. whose link with the development of persistence is yet to be resolved. The present study demonstrates the action of selective inhibitors on NR as well as in the survival of Mycobacterium smegmatis using Wayne{\textquoteright}s model. During gradual shift down to anaerobic stage in Wayne{\textquoteright}s model, conversion of nitrate to nitrite became apparent in M. smegmatis. More than 97 percent inhibition was observed for the conversion of nitrate to nitrite by azide (0.05 mM) and thiocyanate (20 mM) in both whole-cell as well as its cell-free lysate, respectively. Under identical condition, chlorate (20 mM) inhibited nitrate reduction by 67 and 10 percent, respectively. At these concentrations, neither of azide, thiocyanate nor chlorate had any significant effect on cell growth under aerobic condition. In Wayne{\textquoteright}s culture model, thiocyanate and chlorate inhibited the growth of M. smegmatis by almost 2 logs at the same concentrations whereas azide inhibited by almost 1.75 log when added at the time of inoculation. Exposure of same culture at 96 h after inoculation in Wayne{\textquoteright}s model to these inhibitors showed 1.74, 1.95 and 2.37 log inhibition of viable cells with respect to azide, thiocyanate and chlorate. These findings further indicated that NR inhibitors kill the bacilli at anaerobic stage under the experimental condition mentioned. Metronidazole (MTZ) (2 mM) and Nitrofurantoin (NIT) (0.3 mM) reduced the cell number at both stages by \< 0.7log. They did not have any effect on NR. Altogether, the results clearly indicate that NR-specific inhibitors could become more promising in killing the bacilli at anaerobic stage than the available conventional drugs. (c) 2006 Elsevier Ltd. All rights reserved.

}, keywords = {Mycobacterium smegmatis, nitrate reductase, Wayne model}, issn = {0882-4010}, doi = {10.1016/j.micpath.2006.04.006}, author = {Khan, Arshad and Sarkar, Dhiman} } @article { ISI:000262590700009, title = {Presence of a functional nitrate assimilation pathway in mycobacterium smegmatis}, journal = {Microbial Pathogenesis}, volume = {44}, number = {1}, year = {2008}, month = {JAN}, pages = {71-77}, publisher = {ACADEMIC PRESS LTD ELSEVIER SCIENCE LTD}, address = {24-28 OVAL RD, LONDON NW1 7DX, ENGLAND}, abstract = {

Ability of Mycobacterium smegmatis to assimilate nitrate was evaluated in its active and dormant phase. Nitrate (10 mM), nitrite (0.5 mM) and ammonia (10 mM)allowed growth of M. smegmatis concomitant with their complete depletion from the culture in 144, 120 and 96 h, respectively, when used as sole nitrogen Source. Azide (50 mu M) stopped the growth of M. smegmatis when nitrate was used as sole nitrogen source. L-methionine-S-sulfoximine (L-MSO), which is a well-known inhibitor of glutamine synthetase, an enzyme also involved in nitrogen metabolic pathway, when applied at 10 mu g/ml concentration, completely inhibited the growth of the organism when nitrate or nitrite was used as sole nitrogen source. There was no effect of either azide or L-MSO at above concentrations on the growth of the organism when asparagine or ammonia was used as sole nitrogen source. More significantly, utilization of nitrate, nitrite and ammonia continued even in oxygen depletion induced dormant culture at the rates of 289, 25 and 354 mu M/day, respectively. These rates were 5-8 times slower than the rates of 1966, 127 and 2890 mu M/day, respectively, in active replicating phase. In the presence of azide (50 mu M) and L-MSO (10 mu g/ml), 2.1 and 1.51 logs reduction in viability of dormant M. smegmatis was observed using nitrate and nitrite, respectively, as sole nitrogen source. Altogether, the results indicated the presence of nitrate assimilation pathway operating in both active and dormant stage of M. smegmatis. (C) 2007 Elsevier Ltd. All rights reserved.

}, keywords = {Dormant bacilli, Glutamine synthetase, L-methionine-S-sulfoximine, Mycobacterium smegmatis, Nitrate assimilation}, issn = {0882-4010}, doi = {10.1016/j.micpath.2007.08.006}, author = {Khan, Arshad and Akhtar, Shamim and Ahmad, Jawid N. and Sarkar, Dhiman} } @article { ISI:000356251500001, title = {Qualitative and quantitative proteomic analysis of vitamin C induced changes in mycobacterium smegmatis}, journal = {Frontiers in Microbiology}, volume = {6}, year = {2015}, month = {MAY}, pages = {Article Number: 451}, publisher = {FRONTIERS RESEARCH FOUNDATION}, address = {PO BOX 110, LAUSANNE, 1015, SWITZERLAND}, abstract = {

Vitamin C is a critical dietary nutrient in human which has a wide range of regulatory effects on gene expression and physiology of Mycobacterium tuberculosis that leads to a dormant drug-tolerant phenotype. In the presence of iron, vitamin C shows a high bactericidal activity even in the drug resistant phenotype of M. tuberculosis. The regulatory mechanisms underlying vitamin C induced adaptations are largely unknown due to lack of functional genomics data in this field. In this study, we attempt to characterize the direct effect of vitamin C treatment on the physiology of actively growing Mycobacterium smegmatis. The study chose M. smegmatis as it is a fast-growing bacterium and a non-pathogenic model system which shares many physiological features with the pathogenic M. tuberculosis including dormancy and its regulation. The proteomic adaptation of M. smegmatis on vitamin C treatment demonstrates the important changes in cellular and metabolic process such as reversal of tricarboxylic acid cycle, decrease in ATP synthesis, decrease in iron acquisition and storage, and induction of dormancy regulators WhiB3, PhoP, and Lsr2.

}, keywords = {dormancy, Mycobacterium smegmatis, proteomics, tuberculosis, vitamin C}, issn = {1664-302X}, doi = {10.3389/fmicb.2015.00451}, author = {Mishra, Abhishek and Sarkar, Dhiman} }