Biology subjects

Baishya, D.

Publications and source records attributed to Baishya, D..

4 recordsLinked to original sources

bioRxiv2022

Targeting tumor stemness switch phenotype by activating pathogen induced stem cell niche defense

Cancer stem cells (CSCs) reside in their tumor microenvironment (TME) niches, which are often hypoxic. Previously, we found that hypoxia and oxidative stress prevalent in TME may reprogram CSCs to a highly aggressive and inflammatory phenotype, the tumor stemness switch (TSS) phenotype. We previously reported a "stem cell niche defense" mechanism in bone marrow and lung mesenchymal stem cell niche against pathogen. Pathogen induced bystander apoptosis (PIBA) of stem cells harboring intracellular pathogen may be part of this defense mechanism. We speculate that the TSS phenotype may also activate this niche defense mechanism to defend their TME niche against pathogen and therefore could be exploited to target CSCs. Here we report that CSCs of TSS phenotype enriched in post-hypoxia ABCG2+ CSCs of several cell lines of diverse tumors including oral squamous cell carcinoma cell line SCC-25 exhibited bystander apoptosis when infected with either Bacillus Calmette Guerin (BCG) or mutant Mycobacterium tuberculosis (Mtb) strain 18b. The conditioned media (CM) of the infected cells not only exhibited marked anti-tumor activity in vivo, but also showed significant anti-microbial activity. A detailed mechanisms study revealed that some of the infected ABCG2+ CSCs underwent pyroptosis and released a high mobility group box protein 1 (HMGB1)/p53 death signal that can induce a toll like receptor (TLR) 2/4 mediated bystander apoptosis. Thus, our findings suggest that PIBA can be utilized to activate the "niche defense" mechanism in TSS phenotype, which not only target the TSS, but also exhibit marked anti-tumor activity in vivo.

cancer biology↗

bioRxiv2020

Coronavirus activates a stem cell-mediated defense mechanism that accelerates the activation of dormant tuberculosis: implications for the COVID-19 pandemic

We postulate that similar to bacteria, adult stem cells may also exhibit an innate defense mechanism to protect their niche. Here, we provide preliminary data on stem cell based innate defense against a mouse model of coronavirus, murine hepatitis virus-1 (MHV-1) infection. In a mouse model of mesenchymal stem cell (MSC) mediated Mycobacterium tuberculosis (Mtb) dormancy, MHV-1 infection in the lung exhibited 20 fold lower viral loads than the healthy control mice, suggesting the potential enhancement of an anti-MHV-1 defense by Mtb. This defense mechanism involves the in vivo expansion and reprogramming of CD271+MSCs in the lung to an enhanced stemness phenotype. The reprogrammed MSCs facilitate the activation of stemness genes, intracellular Mtb replication, and extracellular release of Mtb. The conditioned media of the reprogrammed MSCs exhibit direct anti-viral activity in an in vitro model of MHV-1 induced toxicity to type II alveolar epithelial cells. Thus, our data suggest that reprogrammed MSCs exert a unique innate defense against MHV-1 by activating dormant Mtb. The molecular details of this anti-viral defense mechanism against coronavirus could be further studied to develop a vaccine against COVID-19.

microbiology↗

bioRxiv2020

Exploration of endo-xylanase from novel strain of Bacillus velezensis AG20 isolated from the cave of Meghalaya

Cave sets the example of extreme ecological niche and habitat for diversified microorganisms. Present study involved in the isolation of endoxylanase producing novel strain Bacillus velezensis AG20 from the Krem Phyllut cave, Meghalaya, India. Culture dependent studies, molecular phylogentics, RNA secondary folding pattern based on 16S rDNA substantiated the identity of this novel strain. Bacillus velezensis AG20 revealed the superbug quality having resistance against various class of broad-spectrum antibiotics. Bacillus velezensis AG20 revealed biofilm formation over the cell surface in FESEM. Highest cell biomass and xylanase production supported in TB medium, further purified partially to 5.3 fold with 21% yield. Molecular weight of the purified xylanase found to be 45 kDa. Enzyme kinetics and pattern of hydrolysis revealed the evidence for the selection of linear birchwood xylan with Vmax = 21.0 {+/-} 3.0 U/ml, Km = 1.25 mg/ml, Kcat = 1.75/s at optimum pH 7 and temperature 50{degrees}C also found significant statistically in Taguchis orthogonal design. Conversely, ruled out any exoacting activity against synthetic pNP-xylopyranoside substrate. Endo-xylanase isolated from Bacillus velezensis AG20 was moderately thermostable over temperatures 50 and 60{degrees}C. Time dependent hydrolysis of agro-waste sugar cane bagasse depicted the production of xylooligosaccharides (XOS) predominantly xylobiose, xylotriose and xylotetrose. Purified mixed XOS hold their prebiotic potential by promoting the growth of probiotics Bifidobacterium and Lactobacillus as well as high stability (~90%) against systemic fluids. Mixed XOS (300 g/ml) displayed anti-proliferation activities by reducing the growth of HT-29 and Caco-2 cells significantly 90% and 75%, respectively, after 48 h. IMPORTANCEExtremophiles dwelling inside the caves have laden with the extraordinary capabilities of bioconversion by nature. The pristine ecological niche inside the cave, absence of proper light and air, supports the livelihood of novel microorganisms. In India, Meghalaya is hoisting longest caves in the East Khasi Hills, providing conducive environment for novel bacterial strains. With the prime objective of isolating novel bacterial strains that produce extracellular xylanase our studies have been carried out. Considering the present industrial demand for nutraceutical, prebiotics, anti-proliferating agents and biofuels by the conversion of lignocellulosic biomass (LCB), novel enzymes are required. Xylanases from bacterial origin play a significant role in conversion of LCB into oligosaccharides. Therefore, exploration and characterization of xylanase producing novel isolate from cave may pave the new arena for the production of prebiotic and anti-inflammatory oligosaccharides from agro-waste.

microbiology↗

bioRxiv2019

Isolation of a novel strain of Lactic Acid Bacteria from traditionally fermented common lime (Citrus aurantifolia) of Assam, India and analysis of exopolymeric substances produced by the strain

A gram positive, rod shaped and catalase negative strain of Lactic Acid Bacteria was isolated from traditionally fermented common lime (Citrus aurantifolia) of Assam, North-East India. Bacterial identification was done by using conventional morphological and biochemical methods as well as advanced molecular technique. Traditionally fermented lime juice was serially diluted on selective culture medium and growth of translucent, ropy bacterial colony was observed in the culture plate. Isolated bacteria were identified up to species level by using ribosomal RNA (rRNA) gene sequencing technique. Based on nucleotide homology and phylogenetic analysis the isolate was found to be a strain of Lactobacillus delbrueckii. This is the first report of finding this sub species of Lactic Acid Bacteria in citrus fruit product. The sequence determined in this study has been deposited in the GenBank database with sequential accession number KT198973. The bacterial isolate also produced exopolysaccharide when grown in chemically defined medium. Fourier Transform Infrared Spectroscopy (FTIR) was done for chemical and compositional characterization of partially purified exopolysaccharide.

microbiology↗