Hemant J. Purohit

Hemant J. Purohit

National Environmental Engineering Research Institute, CSIR

Title: Dynamic gene network selection through stress modulation: An E. coli model


Hemant J Purohit has completed the Ph D in 1986 from Department of Microbiology & Biochemistry Nagpur University India in fermentation microbiology. He did two Post-Doctoral programs (Commonwealth Post -Doctoral Fellowship, Department of Biochemistry, University of Hull, UK & Fogarty Fellowship at Lab of Molecular Biology, NINDS, NIH, Bethesda, USA) before joining as Scientist in Year 1992, at National Environmental Engineering Research Institute (CSIR-NEERI). Currently he is Head, Department of Genomics (CSIR-NEERI). He has published more than 150 papers in reputed journals and serving as an editorial board member of three international journals.


The shifting trend of functional physiology is decided through cross-talks between regulators and regulated genes; and this delicate balance of gene expression gets further modulated through stresses such as change in redox or availability of nutrients. Any stress and its after effects are carried to next phase in life cycle and tracing back the gene expression signature could suggest the possible mechanism by which cell still manages and compromises physiology to get the optimum performance. We have created an E.coli model, wherein cells were subjected to a short term hydrogen peroxide stress and the cellular performance was studied in optimal recovery media. The gene network which brings the optimum performance was predicted based on the dynamic gene expression data using a priori selected genes and their expression through GFP reporter system. In the second scenario the cells were trained at different nutritional level and then subjected hydrogen peroxide stress. The affected genes were selected through the microarray expression data. The dynamic expression data of selected genes using GFP reporter system have been modeled to understand stress mediated emerging network which helps in decision making. The study proposes that the cellular performance could be substantially modulated by different regulators and their interactions. The relationship between different regulators dynamically shifts and with that the new interactions emerge with re-defined network rules. Using different qualitative stresses, the study shows how stress specific new regulatory partners and their correlation appears. What emerges out of the above two scenarios is, as and when needed, a genetic functionally active module/clusters that dictates the cell fate.

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