Department of Biological Sciences
Permanent URI for this collectionhttp://localhost:4000/handle/123456789/1922
Browse
7 results
Search Results
Item Metabolomic profiling of biphenyl-induced stress response of Brucella anthropi MAPB-9(Springer Nature, 2025-04) Jha, Prabhat Nath; Paul, Atish TulshiramThe exposure of bacteria to toxic compounds such as polychlorinated biphenyl (PCB) and biphenyl induces an adaptive response at different levels of cell morphology, biochemistry, and physiology. PCB and biphenyl are highly toxic compounds commercially used in the industry. In our previous study, Brucella anthropi MAPB-9 efficiently degraded PCB-77 and biphenyl at a high concentration. In this study, we used metabolomic analyses to understand the metabolic processes occurring in MAPB-9 during exposure to biphenyl. A combination of analytical techniques such as GC-MS/MS and HR-MS study confirmed the complete biphenyl degradation pathway. The intermediate metabolic products identified were cis-2, 3-dihydro-2, 3-dihydroxy biphenyl, 2,3-dihydroxy biphenyl, and 4-dihydroxy-2-oxo-valerate. Further, benzoic acid and 2,3-dihydroxy benzoic acid metabolites identified in the extract revealed the interconnection of biphenyl and benzoic degradation pathways. In addition, the variations in the functioning of the major biochemical pathways in the cells were revealed through changes in the profile of metabolites belonging to glyoxylate, tricarboxylic acid (TCA) cycle, and fatty acid pathways. The exposure to biphenyl inhibited metabolic activity leading to changes in the morphology and metabolism. Despite many adverse changes, the MAPB-9 was able to adapt and grow in the toxic environment undergoing upper and lower biphenyl degradation pathways.Item Characterization of functional amyloid curli in biofilm formation of an environmental isolate Enterobacter cloacae SBP-8. Antonie Van Leeuwenhoek(Springer, 2023-05) Jha, Prabhat Nath; Tare, MeghanaThe biofilm formation by bacteria is a complex process that is strongly mediated by various genetic and environmental factors. Biofilms contribute to disease infestation, especially in chronic infections. It is, therefore important to understand the factors affecting biofilm formation. This study reports the role of a functional amyloid curli in biofilm formation at various abiotic surfaces, including medical devices, by an environmental isolate of Enterobacter cloacae (SBP-8) which has been known for its pathogenic potential. A knockout mutant of csgA, the gene encoding the major structural unit of curli, was created to study the effect of curli on biofilm formation by E. cloacae SBP-8. Our findings confirm the production of curli at 25 °C and 37 °C in the wild-type strain. We further investigated the role of curli in the attachment of E. cloacae SBP-8 to glass, enteral feeding tube, and foley latex catheter. Contrary to the previous studies reporting the curli production below 30 °C in the majority of biofilm-forming bacterial species, we observed its production in E. cloacae SBP-8 at 37 °C. The formation of more intense biofilm in wild-type strain on various surfaces compared to curli-deficient strain (ΔcsgA) at both 25 °C and 37 °C suggested a prominent role of curli in biofilm formation. Further, electron and confocal microscopy studies demonstrated the formation of diffused monolayers of microbial cells on the abiotic surfaces by ΔcsgA strain as compared to the thick biofilm by respective wild-type strain, indicating the involvement of curli in biofilm formation by E. cloacae SBP-8. Overall, our findings provide insight into biofilm formation mediated by curli in E. cloacae SBP-8. Further, we show that it can be expressed at a physiological temperature on all surfaces, thereby indicating the potential role of curli in pathogenesisItem Regulation of Lipid Biosynthesis, Sliding Motility, and Biofilm Formation by a Membrane-Anchored Nucleoid-Associated Protein of Mycobacterium tuberculosis(American Society for Microbiology, 2013-03) Ghosh, SoumitraBacteria use a number of small basic proteins for organization and compaction of their genomes. By their interaction with DNA, these nucleoid-associated proteins (NAPs) also influence gene expression. Rv3852, a NAP of Mycobacterium tuberculosis, is conserved among the pathogenic and slow-growing species of mycobacteria. Here, we show that the protein predominantly localizes in the cell membrane and that the carboxy-terminal region with the propensity to form a transmembrane helix is necessary for its membrane localization. The protein is involved in genome organization, and its ectopic expression in Mycobacterium smegmatis resulted in altered nucleoid morphology, defects in biofilm formation, sliding motility, and change in apolar lipid profile. We demonstrate its crucial role in regulating the expression of KasA, KasB, and GroEL1 proteins, which are in turn involved in controlling the surface phenotypes in mycobacteria.Item Overexpression of Rice Wall-Associated Kinase 25 (OsWAK25) Alters Resistance to Bacterial and Fungal Pathogens(PLOS Biology, 2016-01) Sharma, RitaWall-associated kinases comprise a sub-family of receptor-like kinases that function in plant growth and stress responses. Previous studies have shown that the rice wall-associated kinase, OsWAK25, interacts with a diverse set of proteins associated with both biotic and abiotic stress responses. Here, we show that wounding and BTH treatments induce OsWAK25 transcript expression in rice. We generated OsWAK25 overexpression lines and show that these lines exhibit a lesion mimic phenotype and enhanced expression of rice NH1 (NPR1 homolog 1), OsPAL2, PBZ1 and PR10. Furthermore, these lines show resistance to the hemibiotrophic pathogens, Xanthomonas oryzae pv. oryzae (Xoo) and Magnaporthe oryzae, yet display increased susceptibility to necrotrophic fungal pathogens, Rhizoctonia solani and Cochliobolus miyabeanus.Item Isolation and characterization of an arsenic-resistant bacterium from a bore-well in West Bengal, India(Springer Nature, 2009) Chowdhury, RajdeepAn arsenic-resistant bacterium, strain KRPC10YT, was isolated from arsenic-infested bore-well of West Bengal, India. The bacterium was resistant to exceeding concentrations of arsenate (30 mM) and arsenite (20 mM). The bacterium was Gram-positive, rod-shaped, motile and yellowish to orange-pigmented. The major fatty acids were anteiso-C15:0, iso-C15∶0. The DNA G+C content was 49 mol %. Based on its phenotypic, chemotaxonomic and phylogenetic characteristics, it was identified as a member of the genusPlanococcus and is the first knownPlanococcus resistant to arsenic. KRPC10YTT was positive for indole, catalase, tolerated up to 12.0% NaCl and exhibited phenotypic differences with other type strains of genusPlanococcus. Strain KRPC10YT thus could be a novel species of the genusPlanococcus. The type strain is KRPC10YT (= MTCC7758T, =JCM 13947T).Item Arsenic extrusion and energy derivation as survival mechanism in a novel exiguobacterium isolated from arsenic contaminated groundwater of West Bengal(IASIR, 2014) Chowdhury, RajdeepThe Bengal-Delta plain at Indo-Bangladesh border is severely affected with groundwater arsenic contamination. The microbial diversity of this site is totally uncharacterized. Here we report the existence of a novel Exiguobacterium strain that could thrive under high arsenic concentrations in the arsenic-infested water of the above region. Drinking water was sampled for presence of bacterial isolates. Analysis of the 16SrRNA sequence of the bacteria isolated revealed them to be members representing various genera. Of particular interest was a new species of genera Exiguobacterium (=MTCC 7757T=JCM 13946T) that thrived in extremely high arsenic concentration, arsenate (30mM) and arsenite (20mM). The growth-rate of the bacterium cultured in arsenate-supplemented medium increased significantly; it gained metabolic energy from arsenate-amended aerobic growth conditions. On analysis of the ars-operon, the strain was positive for arsB, but the genetic contribution to arsenate reduction (arsC) was not recognized, though a differential arsenate reductase activity could be observed. An increased expression of arsB, as an associated process to arsenate reduction, confirmed that arsenic extrusion principle worked behind its survival. Identification of such a bacterium could add to the diversity of bacteria specific to that geographical location and also help us in delineating putative novel arsenic resistance mechanisms operative for survivalItem Design and Synthesis of Imidazo/Benzimidazo[1,2-c]quinazoline Derivatives and Evaluation of Their Antimicrobial Activity(ACS, 2018) Jha, Prabhat N.; Kumar, AnilA new class of fused quinazolines has been designed and synthesized via copper-catalyzed Ullmann type C–N coupling followed by intramolecular cross-dehydrogenative coupling reaction in moderate to good yields. The synthesized compounds were tested for in vitro antibacterial activity against three Gram negative (Escherichia coli, Pseudomonas putida, and Salmonella typhi) and two Gram positive (Bacillus subtilis, and Staphylococcus aureus) bacteria. Among all tested compounds, 8ga, 8gc, and 8gd exhibited promising minimum inhibitory concentration (MIC) values (4–8 μg/mL) for all bacterial strains tested as compared to the positive control ciprofloxacin. The synthesized compounds were also evaluated for their in vitro antifungal activity against Aspergillus niger and Candida albicans and compounds 8ga, 8gc, and 8gd having potential antibacterial activity also showed pronounced antifungal activity (MIC values 8–16 μg/mL) against both strains. The bactericidal assay by propidium iodide and live–dead bacterial cell screening using a mixture of acridine orange/ethidium bromide (AO/Et·Br) showed considerable changes in the bacterial cell membrane, which might be the cause or consequence of cell death. Moreover, the hemolytic activity for most potent compounds (8ga, 8gc, and 8gd) showed their safety profile toward human blood cells.