Govind Sah - Academia.edu (original) (raw)
Papers by Govind Sah
Journal of Microbiology and Antimicrobials, Jan 30, 2011
Aqueous ethanolic extract of four medicinal plants were subjected to in vitro antibacterial assay... more Aqueous ethanolic extract of four medicinal plants were subjected to in vitro antibacterial assay against human pathogenic Escherichia coli, Salmonella typhi, Salmonella paratyphi, Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa employing cup diffusion method. Among four plants tested Eugenia caryophyllata (Clove) was found to be the most effective against S. typhi. All the plants were ineffective against E. coli and K. pneumonia. Achyranthes bidentata was found to be ineffective against all the tested organisms. The largest zone of inhibition (22 mm) was obtained with E. caryophyllata against S. typhi and Minimum Bactericidal Concentration (MBC) value of 5 mg/l was obtained with Azadirachta indica against S. typhi. K. pneumoniae and E. coli were found to be resistant with all the plant extracts. A qualitative phytochemical analysis was performed for the detection of alkaloids, glycosides, terpenoids, steroids, flavonoids, tannins and reducing sugars. Thin layer chromatography was also performed using solvent system chloroform, methanol and water (10:10:3) for the analysis of lipid present in plant extract. The present study will be successful in identifying candidate plant with different antimicrobial activity which could be further exploited for isolation and characterization of the novel phytochemicals in the treatment of infectious disease especially in light of the emergence of drug-resistant microorganisms and the need to produce more effective antimicrobial agents.
A wide range of biological systems - from microbial swarms to bird flocks, display emergent behav... more A wide range of biological systems - from microbial swarms to bird flocks, display emergent behaviors driven by coordinated movement of individuals. To this end, individual organisms interact by recognizing their kin and adjusting their motility based on others around them. However, even in the best-studied systems, the mechanistic basis of the interplay between kin recognition and motility coordination is not understood. Here, using a combination of experiments and mathematical modeling, we uncover the mechanism of an emergent social behavior in Myxococcus xanthus. By overexpressing cell surface adhesins, TraA and TraB, involved in kin recognition, large numbers of cells adhere to one another and form organized macroscopic circular aggregates that spin clockwise or counterclockwise. Mechanistically, TraAB adhesion results in sustained cell-cell contacts that trigger cells to suppress cell reversals, and circular aggregates form as the result of cells' ability to follow their ow...
mBio, 2021
Many bacterial species use diverse systems to deliver bacteriocins or toxins to neighboring compe... more Many bacterial species use diverse systems to deliver bacteriocins or toxins to neighboring competing cells. These systems are often selective in targeting cells that are related to themselves and therefore compete in the same niches for resources.
Current Opinion in Microbiology, 2020
Myxobacteria conduct complex social traits that requires populations to be highly related and dev... more Myxobacteria conduct complex social traits that requires populations to be highly related and devoid of exploiters. To enrich for clonal cells in populations, they employ kin discrimination mechanisms. One key system involves a polymorphic cell surface receptor, TraA, which recognizes self by homotypic interactions with neighboring myxobacterial cells. Recent studies revealed that TraA and its partner TraB are fluid outer membrane proteins that coalesce into foci upon recognition of kin. The formation of foci leads to transient membrane fusion junctions and the bidirectional exchange of outer membrane components that facilitates cooperative behaviors. Additionally, expansive suites of polymorphic lipoprotein toxins are exchanged, which act as selfidentity barcodes that exquisitely discriminate against nonself to assemble homogenous populations.
Molecular Microbiology, 2020
Cells interact with their surrounding environment through surface proteins. However, knowledge ga... more Cells interact with their surrounding environment through surface proteins. However, knowledge gaps remain in understanding how these important types of proteins are transported and anchored on the cell surface. In the Gram-negative social bacterium, Myxococcus xanthus, a putative Cterminal sorting tag (MYXO-CTERM) is predicted to help direct 34 different proteins onto the cell surface. Here we investigate the sorting pathway for MYXO-CTERM proteins by using the TraA cell surface receptor as a model. Deleting this motif from TraA abolishes cell surface anchoring and results in extracellular secretion. Our findings indicate that conserved cysteines within the MYXO-CTERM are post-translationally modified and are required for TraA cell surface localization and function. A region immediately upstream of these residues is predicted to be disordered and removing this motif caused a secretion defect and blocked cell surface anchoring. We further show that the type II secretion system is required for translocation across the outer membrane and that a cysteine-rich region directs TraA to the T2SS. Similar results were found with another MYXO-CTERM protein indicating our findings can be generalized. Further, we show the universal distribution of MXYO-CTERM motif across the Myxococcales order and provide a working model for sorting of these proteins.
Aqueous ethanolic extract of four medicinal plants were subjected to in vitro antibacterial assay... more Aqueous ethanolic extract of four medicinal plants were subjected to in vitro antibacterial assay against human pathogenic Escherichia coli, Salmonella typhi, Salmonella paratyphi, Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa employing cup diffusion method. Among four plants tested Eugenia caryophyllata (Clove) was found to be the most effective against S. typhi. All the plants were ineffective against E. coli and K. pneumonia. Achyranthes bidentata was found to be ineffective against all the tested organisms. The largest zone of inhibition (22 mm) was obtained with E. caryophyllata against S. typhi and Minimum Bactericidal Concentration (MBC) value of 5 mg/l was obtained with Azadirachta indica against S. typhi. K. pneumoniae and E. coli were found to be resistant with all the plant extracts. A qualitative phytochemical analysis was performed for the detection of alkaloids, glycosides, terpenoids, steroids, flavonoids, tannins and reducing sugars. Thin layer...
Journal of Microbiology and Antimicrobials, Jan 30, 2011
Aqueous ethanolic extract of four medicinal plants were subjected to in vitro antibacterial assay... more Aqueous ethanolic extract of four medicinal plants were subjected to in vitro antibacterial assay against human pathogenic Escherichia coli, Salmonella typhi, Salmonella paratyphi, Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa employing cup diffusion method. Among four plants tested Eugenia caryophyllata (Clove) was found to be the most effective against S. typhi. All the plants were ineffective against E. coli and K. pneumonia. Achyranthes bidentata was found to be ineffective against all the tested organisms. The largest zone of inhibition (22 mm) was obtained with E. caryophyllata against S. typhi and Minimum Bactericidal Concentration (MBC) value of 5 mg/l was obtained with Azadirachta indica against S. typhi. K. pneumoniae and E. coli were found to be resistant with all the plant extracts. A qualitative phytochemical analysis was performed for the detection of alkaloids, glycosides, terpenoids, steroids, flavonoids, tannins and reducing sugars. Thin layer chromatography was also performed using solvent system chloroform, methanol and water (10:10:3) for the analysis of lipid present in plant extract. The present study will be successful in identifying candidate plant with different antimicrobial activity which could be further exploited for isolation and characterization of the novel phytochemicals in the treatment of infectious disease especially in light of the emergence of drug-resistant microorganisms and the need to produce more effective antimicrobial agents.
A wide range of biological systems - from microbial swarms to bird flocks, display emergent behav... more A wide range of biological systems - from microbial swarms to bird flocks, display emergent behaviors driven by coordinated movement of individuals. To this end, individual organisms interact by recognizing their kin and adjusting their motility based on others around them. However, even in the best-studied systems, the mechanistic basis of the interplay between kin recognition and motility coordination is not understood. Here, using a combination of experiments and mathematical modeling, we uncover the mechanism of an emergent social behavior in Myxococcus xanthus. By overexpressing cell surface adhesins, TraA and TraB, involved in kin recognition, large numbers of cells adhere to one another and form organized macroscopic circular aggregates that spin clockwise or counterclockwise. Mechanistically, TraAB adhesion results in sustained cell-cell contacts that trigger cells to suppress cell reversals, and circular aggregates form as the result of cells' ability to follow their ow...
mBio, 2021
Many bacterial species use diverse systems to deliver bacteriocins or toxins to neighboring compe... more Many bacterial species use diverse systems to deliver bacteriocins or toxins to neighboring competing cells. These systems are often selective in targeting cells that are related to themselves and therefore compete in the same niches for resources.
Current Opinion in Microbiology, 2020
Myxobacteria conduct complex social traits that requires populations to be highly related and dev... more Myxobacteria conduct complex social traits that requires populations to be highly related and devoid of exploiters. To enrich for clonal cells in populations, they employ kin discrimination mechanisms. One key system involves a polymorphic cell surface receptor, TraA, which recognizes self by homotypic interactions with neighboring myxobacterial cells. Recent studies revealed that TraA and its partner TraB are fluid outer membrane proteins that coalesce into foci upon recognition of kin. The formation of foci leads to transient membrane fusion junctions and the bidirectional exchange of outer membrane components that facilitates cooperative behaviors. Additionally, expansive suites of polymorphic lipoprotein toxins are exchanged, which act as selfidentity barcodes that exquisitely discriminate against nonself to assemble homogenous populations.
Molecular Microbiology, 2020
Cells interact with their surrounding environment through surface proteins. However, knowledge ga... more Cells interact with their surrounding environment through surface proteins. However, knowledge gaps remain in understanding how these important types of proteins are transported and anchored on the cell surface. In the Gram-negative social bacterium, Myxococcus xanthus, a putative Cterminal sorting tag (MYXO-CTERM) is predicted to help direct 34 different proteins onto the cell surface. Here we investigate the sorting pathway for MYXO-CTERM proteins by using the TraA cell surface receptor as a model. Deleting this motif from TraA abolishes cell surface anchoring and results in extracellular secretion. Our findings indicate that conserved cysteines within the MYXO-CTERM are post-translationally modified and are required for TraA cell surface localization and function. A region immediately upstream of these residues is predicted to be disordered and removing this motif caused a secretion defect and blocked cell surface anchoring. We further show that the type II secretion system is required for translocation across the outer membrane and that a cysteine-rich region directs TraA to the T2SS. Similar results were found with another MYXO-CTERM protein indicating our findings can be generalized. Further, we show the universal distribution of MXYO-CTERM motif across the Myxococcales order and provide a working model for sorting of these proteins.
Aqueous ethanolic extract of four medicinal plants were subjected to in vitro antibacterial assay... more Aqueous ethanolic extract of four medicinal plants were subjected to in vitro antibacterial assay against human pathogenic Escherichia coli, Salmonella typhi, Salmonella paratyphi, Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa employing cup diffusion method. Among four plants tested Eugenia caryophyllata (Clove) was found to be the most effective against S. typhi. All the plants were ineffective against E. coli and K. pneumonia. Achyranthes bidentata was found to be ineffective against all the tested organisms. The largest zone of inhibition (22 mm) was obtained with E. caryophyllata against S. typhi and Minimum Bactericidal Concentration (MBC) value of 5 mg/l was obtained with Azadirachta indica against S. typhi. K. pneumoniae and E. coli were found to be resistant with all the plant extracts. A qualitative phytochemical analysis was performed for the detection of alkaloids, glycosides, terpenoids, steroids, flavonoids, tannins and reducing sugars. Thin layer...