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R J, R.

Publications and source records attributed to R J, R..

2 recordsLinked to original sources

Spatial separation of Streptomyces aerial mycelium during fermentation enhances secondary metabolite production

Conditioning of morphology is an effective technique to enhance secondary metabolite production by Streptomyces. Here we report a novel conditioning method employing glass marbles in batch cultures to enhance secondary metabolite production by Streptomyces sp. The marbles seem to spatially separate aerial and submerged mycelia in the flask which was necessary for the qualitative and quantitative enhancement of metabolite production of secondary metabolites. The method also offers shorter incubation period compared to conventional methods for effective production. Further, using a combination of this method and response surface methodology we could enhance the production of antimycobacterial molecules chrysomycin A and B significantly. ImportanceRediscovery of existing molecules and lack of techniques to induce production of secondary metabolites are the major bottlenecks associated with drug discovery of novel bioactive molecules from Streptomyces, the major source of marketable drugs today. We found a new method to increase the diversity and quantity of secondary metabolites in two Streptomyces species. This method thus enhances the chance of finding novel active principles from Streptomyces.

microbiology

ESAT-6 of Mycobacterium tuberculosis downregulates cofilin1 and reduces the phagosome acidification in infected macrophages

Mycobacterium tuberculosis when phagocytosed by macrophages is not cleared completely and many of the bacteria remain in phagosomes indefinitely. In this study we considered abnormal retention of filamentous actin on early phagosomes contributing to defective phagosome acidification. The actin depolymerizing protein cofilin1 was found downregulated in macrophages infected with virulent M. tuberculosis. Also, phosphocofilin1, the inactive form of cofilin1, which leads to retention of filamentous actin, and the total filamentous actin itself were found upregulated in macrophages infected with virulent M. tuberculosis. Over expression of constitutively active cofilin1 in macrophages was found to decrease the level of filamentous actin and increase phagosome acidification when infected with virulent M. tuberculosis. The anticancer drug sorafenib which activates cofilin1 in PI3K dependent manner was also found to decrease the filamentous actin level and increase phagosome acidification. Cofilin1, known to be positively regulated by superoxide was found to be downregulated by ESAT-6 of M. tuberculosis where the latter is known to reduce ROS in macrophages. Ectopic expression of ESAT-6 in macrophages was found to downregulate cofilin1, increase filamentous actin and to transform the macrophages more spindle shaped. ESAT-6 was also found to decrease phagosome acidification in macrophages infected with an avirulent M. tuberculosis strain. Finally, this study proposes a role for the amino acid methionine in resisting ROS by creating M93 mutants of ESAT-6.

immunology