Biology subjects

Jagdish, S.

Publications and source records attributed to Jagdish, S..

3 recordsLinked to original sources

bioRxiv2025

Identification of 4-Amino-2-Nitrophenol as a novel inducer of phenotypic antibiotic resistance in Escherichia coli: roles of Lon protease and its substrate MarA

In prokaryotes, the energy-dependent protein degradation is controlled primarily by two ATP-dependent proteases, Lon and Clp. This study investigates the roles of the Lon protease in the metabolism of 2,4-dinitrophenol (2,4-DNP), a toxic industrial compound, in Escherichia coli (E. coli). During the study, an observation was made that the absence of Lon protease resulted in an enhanced conversion of yellow coloured 2,4-DNP to a reddish-brown product. This study aims to characterise the compound observed in the media with wild type (WT) and {Delta}lon strains, understand the mechanisms of 2,4-DNP conversion and decipher the roles of Lon protease in the conversion of 2,4-DNP. UV-visible and LC-MS analyses revealed differences in the conversion products between the WT and {Delta}lon strains. One of the substrates of Lon protease is MarA, a transcription factor. Growth studies with different mutants and trans-complemented strains demonstrated MarA-dependent conversion. The bathochromic shift of spectral peaks suggested a reduction process and possible involvement of nitroreductase enzymes. Indeed, the expression of two nitroreductases, nfsA and nfsB, increased with 2,4-DNP and was dependent on MarA. Importantly, the production of the reddish-brown product was lower in strains lacking nfsA or nfsB. Finally, LC-MS analysis identified one of the conversion products of 2,4-DNP to be 4-Amino-2-nitrophenol (4,2-ANP). Dose studies with purified 4,2-ANP demonstrated that it did not lower the growth of E. coli (unlike 2,4-DNP) but induced phenotypic antibiotic resistance (like 2,4-DNP). This study contributes to our understanding of biological treatment of nitroaromatics and may offer insights into environmental pollution mitigation strategies. ImportanceThis study identifies the roles of Lon protease and its substrate MarA in inducing nitroreductases, NfsA and NfsB, in reducing toxic 2,4-DNP to less toxic 4,2-ANP, a novel inducer of phenotypic antibiotic resistance. This study contributes to understanding the biological treatment of nitroaromatics, offering insights into environmental pollution mitigation strategies and the development of efficient bioremediation techniques.

microbiology↗

bioRxiv2023

Interferon-γ lowers tumour growth by increasing glycolysis and lactate production in a nitric oxide-dependent manner: implications for cancer immunotherapy

Interferon-gamma (IFN-{gamma}), the sole member of the type-II interferon family, is well known to protect the host from infectious diseases as well as mount anti-tumour responses. The amounts of IFN-{gamma} in the tumour microenvironment determine the host responses against tumours; however, several tumours employ evasive strategies by responding to low IFN-{gamma} signalling. In this study, the response of various tumour cell lines to IFN-{gamma} was studied in vitro. IFN-{gamma}-activation increases glycolytic flux and reduces mitochondrial function in a nitric oxide (NO)- and reactive oxygen species (ROS)-dependent manner in the H6 hepatoma tumour cell line. The higher glycolysis further fuelled NO and ROS production, indicating a reciprocal regulation. These processes are accompanied by Hypoxia inducing factor (HIF)-1 stabilization and HIF-1-dependent augmentation of the glycolytic flux. The IFN-{gamma} enhancement of lactate production also occurred in other NO-producing cell lines: RAW 264.7 monocyte/macrophage and Renca renal adenocarcinoma. However, two other tumour cell lines, CT26 colon carcinoma and B16F10 melanoma, did not produce NO and lactate upon IFN-{gamma}-activation. HIF-1 stabilization upon IFN-{gamma}-activation led to lower cell growth of B16F10 but not CT26 cells. Importantly, the IFN-{gamma}-activation of both CT26 and B16F10 cells demonstrated significant cellular growth reduction upon metabolic rewiring by exogenous administration of potassium lactate. Clinical studies have shown the crucial roles of IFN-{gamma} for successful cancer immunotherapies involving checkpoint inhibitors and chimeric antigen receptor T cells. The positive implications of this study on the metabolic modulation of IFN-{gamma} activation on heterogeneous tumour cells are discussed.

immunology↗

bioRxiv2023

Global transcriptome analysis reveals Salmonella Typhimurium employs the nitrate-dependent anaerobic pathway to combat bile stress

Salmonella Typhimurium is an enteric pathogen that is highly tolerant to bile. Next-generation mRNA sequencing was performed to analyse the stress and adaptive responses of S. Typhimurium to bile. We identified the cellular pathways affected during bile stress in wild type (WT) and a mutant lacking cspE ({Delta}cspE), which plays an essential role in protection from bile stress. We observed transcriptional upregulation of several genes involved in nitrate metabolism, in response to bile stress. These genes were also differentially expressed between the bile-resilient WT and the bile-sensitive {Delta}cspE strain. To understand the role of nitrate metabolism in bile stress response, we generated a strain lacking fnr ({Delta}fnr), which is the global regulator of nitrate metabolism in S. Typhimurium. fnr was highly induced in the bile treated WT strain but not in the {Delta}cspE strain. Notably, the {Delta}fnr strain was susceptible to bile-mediated killing. Our studies revealed a new role for fnr in mediating the bile stress response. In addition, a strain lacking arcA ({Delta}arcA), a two-component system response regulator involved in anaerobic metabolism, also showed a marked reduction in growth in presence of bile. This corroborated the significance of anaerobic metabolism in S. Typhimurium bile tolerance. Importantly, overexpression of fnr and arcA lowered reactive oxygen species and significantly enhanced the survival of the bile-sensitive {Delta}cspE strain. We also observed that S. Typhimurium pre-treated with nitrate displayed better growth in the presence of bile. Together, these results demonstrate that nitrate-dependent anaerobic metabolism promotes adaptation of S. Typhimurium to bile. ImportanceSalmonella Typhimurium, as an enteric pathogen, manifests an extreme example of bile tolerance. This study describes the diverse metabolic changes at the level of transcriptome in S. Typhimurium exposed to bile. We identified the differential expression of several genes involved in anaerobic metabolism between bile-tolerant WT and bile-sensitive {Delta}cspE strains. Two major regulators of anaerobic metabolism, fnr and arcA, support the growth of S. Typhimurium in bile. Our results highlight that, in presence of bile, S. Typhimurium activates genes involved in anaerobic metabolism, specifically nitrate metabolism, that improves survival of bacteria during bile stress.

microbiology↗