Biology subjects

Majumdar, S.

Publications and source records attributed to Majumdar, S..

8 recordsLinked to original sources

bioRxiv2018

Vitexin alters Staphylococcus aureus surface hydrophobicity to interfere with biofilm formation.

Bacterial surface hydrophobicity is one of the determinant biophysical parameters of bacterial aggregation for being networked to form biofilm. Phytoconstituents like vitexin have long been in use for their antibacterial effect. The present work is aimed to characterise the effect of vitexin on S. aureus surface hydrophobicity and corresponding aggregation to form biofilm. We have found that vitexin shows minimum inhibitory concentration at 252 g/ml against S. aureus. Vitexin reduces cell surface hydrophobicity and membrane permeability at sub-MIC dose of 126 g/ml. The in silico binding analysis showed higher binding affinity of vitexin with surface proteins of S. aureus. Down regulation of dltA, icaAB and reduction in membrane potential under sub-MIC dose of vitexin, explains reduced S. aureus surface hydrophobicity. Vitexin has substantially reduced the intracellular adhesion of planktonic cells to form biofilm through interference of EPS formation, motility and subsequent execution of virulence. This was supported by the observation that vitexin down regulates the expression of icaAB and agrAC genes of S. aureus. In addition, vitexin also found to potentiate antibiofilm activity of sub-MIC dose of gentamicin and azithromycin. Furthermore, CFU count, histological examination of mouse tissue and immunomodulatory study justifies the in vivo protective effect of vitexin from S. aureus biofilm associated infection. Finally it can be inferred that, vitexin has the ability to modulate S. aureus cell surface hydrophobicity which can further interfere biofilm formation of the bacteria.\n\nImportanceThere has been substantial information known about role of bacterial surface hydrophobicity during attachment of single planktonic bacterial cells to any surface and the subsequent development of mature biofilm. This study presents the effect of flavone phytoconstituent vitexin on modulation of cell surface hydrophobicity in reducing formation of biofilm. Our findings also highlight the ability of vitexin in reducing in vivo S. aureus biofilm which will eventually outcompete the corresponding in vitro antibiofilm effect. Synergistic effect of vitexin on azithromycin and gentamicin point to a regime where development of drug tolerance may be addressed. Our findings explore one probable way of overcoming drug tolerance through application of vitexin in addressing the issue of S. aureus biofilm through modulation of cell surface hydrophobicity.

microbiology↗

bioRxiv2017

Receptor guanylyl cyclase C confers protection during oral Salmonella Typhimurium infection by attenuating ileal damage and enhancing cytokine and antimicrobial peptide production

Non-typhoidal Salmonella disease contributes towards significant morbidity and mortality across the world. Host factors including IFN-{gamma}, TNF- and gut microbiota, significantly influence the outcome of Salmonella pathogenesis. However, the entire repertoire of host protective mechanisms contributing to Salmonella pathogenicity is not completely appreciated. Here, we have investigated the roles of receptor guanylyl cyclase C (GC-C) that is predominantly expressed in the intestine, and regulates intestinal cell proliferation and fluid-ion homeostasis. Mice deficient in GC-C (Gucy2c-/-) displayed accelerated mortality following infection via the oral route, in spite of possessing comparative systemic Salmonella infection burden. Survival following intra-peritoneal infection remained similar, indicating that GC-C offered protection via a gut-mediated response. Serum cortisol was higher in Gucy2c-/- mice, in comparison to wild type (Gucy2c+/+) mice, and an increase in infection-induced thymic atrophy, with loss in immature CD4+CD8+ double positive thymocytes, was observed. Accelerated and enhanced damage in the ileum, including submucosal edema, epithelial cell damage, focal tufting and distortion of villus architecture, was seen in Gucy2c-/- mice, concomitant with a larger number of ileal tissue-associated bacteria. Transcription of key mediators in Salmonella-induced inflammation (IL-22/Reg3{beta}) were altered in Gucy2c-/- mice in comparison to Gucy2c+/+ mice. A reduction in fecal Lactobacilli, which are protective against Salmonella infection, was observed in Gucy2c-/- mice. Gucy2c-/- mice cohoused with wild type mice continued to show reduced Lactobacilli and increased susceptibility to infection. Our study therefore suggests that receptor GC-C confers a survival advantage during gut-mediated S. Typhimurium pathogenesis, presumably by regulating Salmonella-effector mechanisms and maintaining a beneficial microbiome.

microbiology↗

bioRxiv2017

Multi-clonal evolution of MDR/XDR M. tuberculosis in a high prevalence setting in Papua New Guinea over three decades

An outbreak of multi-drug resistant tuberculosis has been reported on Daru Island, Papua New Guinea. The Mycobacterium tuberculosis strains driving this outbreak and the temporal accrual of drug resistance mutations have not been described. We analyzed 100 isolates using whole genome sequencing and found 95 belonged to a single modern Beijing strain cluster. Molecular dating suggested acquisition of streptomycin and isoniazid resistance in the 1960s, with virulence potentially enhanced by a mycP1 mutation. The outbreak cluster demonstrated a high degree of co-resistance between isoniazid and ethionamide (80/95; 84.2%) attributed to an inhA promoter mutation combined with inhA and ndh coding mutations. Multidrug resistance (MDR), observed in 78/95 samples, emerged with the acquisition of a typical rpoB mutation together with a compensatory rpoC mutation in the 1980s. There was independent acquisition of fluoroquinolone and aminoglycoside resistance; with evidence of local transmission of extensively-drug resistant (XDR) strains from 2009. These findings underscore the importance of whole-genome sequencing in informing an effective public health response to MDR/XDR M. tuberculosis.

microbiology↗

bioRxiv2017

Bacterial Communication And Relevance Of Quantum Theory

The recent findings confirm that bacteria communicate each other through chemical and electrical signals. Bacteria use chemical signaling molecules which are called as quorum sensing molecules(QSMs) or autoinducers. Moreover, the ion channels in bacteria conduct a long-range electrical signaling within biofilm communities through propagated waves of potassium ions and biofilms attracts other bacterial species too. Both communication process are used by bacteria to make their own survival strategies. In this article, we model this bacterial communication mechanism by complex Ginzburg- Landau equation and discuss the formation of patterns depending on kinematic viscosity associated with internal noise. Again, the potassium wave propagation is described by the non-linear Schrodinger equation in a dissipative environment. By adding perturbation to non-linear Schrodinger equation one arrives at Complex Ginzburg-Landau equation. In this paper we emphasize that at the cellular level(bacteria) we use Complex Ginzburg - Landau equation as a perturbed Nonlinear Schrodinger equation to understand the bacterial communication as well as pattern formation in Biofilms for certain range of kinematic viscosity which can be tested in laboratory experiment. Here, the perturbation is due to the existence of non thermal fluctuations associated to the finite size of the bacteria. It sheds new light on the relevance of quantum formalism in understanding the cell to cell communication.

biophysics↗

bioRxiv2017

The role of coherence in bacterial communication

Bacteria within biofilms can coordinate their behavior through distinct from of communication mechanism1. The well-established cell - to - cell signaling process in bacteria is known as quorum sensing through chemical signaling molecules2-5. Recently, another cell- to - cell communication process based on ion channel mediated electrical signaling6 has also been observed. In this article, we propose a novel approach to explain the role of coherence and phase synchronization in the cell - to - cell bacterial communication. The observable long - range coherent electrical signaling is species independent and it is caused by membrane - potential - dependent modulation of tumbling frequency7-9. Moreover, noise can play a constructive role in enhancing the synchronization of chaotic bacterial communication systems and noise associated with the opening and closing the gate of ion channel induce small kinetic viscosity that make a wave-like pattern in concentration profile of quorum sensing.

biophysics↗

bioRxiv2017

Convection - Diffusion model of talking bacteria

Quorum sensing is cell to cell communication process through chemical signals formally known as autoinducers. When the concentration of quorum sensing molecules reached threshold concentration bacteria are in active state or quorum state. In this article, we propose a mathematical model of quorum sensing systems and study this biological system numerically. Moreover, we compare the different numerical scheme with the batch culture of P.aeruginosa. We observed a negative diffusion coefficient which plays an important role in the quorum sensing mechanism.

biophysics↗

bioRxiv2017

Bacterial Conversations and Pattern Formation

It has long been recognized that certain bacterial groups exhibit cooperative behavioral patterns. Bacteria accomplish such communication via exchange of extracellular signaling molecules called pheromones(autoinducer or quorum sensing molecules). As the bacterial culture grows, signal molecules are released into extracellular milieu accumulate, changing water fluidity. Under such threshold conditions swimming bacterial suspensions impose a coordinated water movement on a length scale of the order 10 to 100 micrometers compared with a bacterial size of the order of 3 micrometers.Here, we investigate the non-local hydrodynamics of the quorum state and pattern formation using forced Burgers equation with Kwak transformation. Such approach resulted in the conversion of the Burgers equation paradigm into a reaction-diffusion system. The examination of the dynamics of the quorum sensing system, both analytically as well as numerically result in similar long-time dynamical behaviour.

biophysics↗

bioRxiv2016

Kinetics of multi-substrate in Beauveria bassiana JUCHE22

The pattern of the biomass specific growth rate is an important focus for many biotechnological applications. Several control strategies have been employed to describe version of the exponential phase of growth of microorganisms. Moreover, in some bioprocesses there is more than one feeding substrates required for the specific growth. Hence, the problem of estimating multiple substrate consumption rates together with the specific growth rate of the microorganism becomes applicable. In this context, the dynamics behaviour of fed-batch process with multiple substrates (dextrose and peptone) and kinetics is further investigated in Beauveria bassiana. Different features of the proposed model are assessed by numerical simulation in different scenarios.

microbiology↗