Biology subjects

Chowdhury, A. R.

Publications and source records attributed to Chowdhury, A. R..

2 recordsLinked to original sources

bioRxiv2022

PHYSIOLOGICAL CHARACTERISTICS OF BACTERIAL DROPLETS INDICATE A CATASTROPHIC CONSEQUENCE WITH AN INCREASE IN IMPACT VELOCITY

Droplet impacts on various surfaces play a profound role in different bio-physiological processes and engineering applications. The current study opens a new realm that investigates the plausible effect of impact velocities on bacteria-laden droplets against a solid surface. We unveiled the alarming consequences of Salmonella Typhimurium (STM) laden drop, carrying out the in vitro and intracellular viability of STM to the impact Weber numbers ranging from 100-750. The specified Weber number range mimics the velocity range occurring during the respiratory processes, especially the airborne dispersion of drops during cough. A thick ring of bacterial deposition was observed in all cases irrespective of impacting velocity and the nutrient content of the bacterial medium. The mechanical properties of the bacterial deposit examined using Atomic Force Microscopy reveals the deformation of bacterial morphology, cushioning effect and adhesion energy to determine the cell-cell interactions. The impact velocity induces the shear stress onto the cell walls of STM, thereby deteriorating the in vitro viability. However, we found that even with compromised in vitro viability, Salmonella retrieved from deposited patterns impacted at higher velocity revealed an increased expression of phoP (the response regulator of the PhopQ two-component system) and uninterrupted intracellular proliferation in macrophages. The inability of STM{Delta} phoP growth in nutrient-rich dried droplets to the subjected impact velocities signifies the predominant role of phoP in maintaining the virulence of Salmonella during desiccation stress. Our findings open a promising avenue for understating the effect of bacteria-laden drop impact and its role in disease spread. O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY

bioengineering↗

bioRxiv2021

The extracellular loops of Salmonella Typhimurium outer membrane protein A (OmpA) maintain the stability of Salmonella containing vacuole (SCV) in murine macrophages and protect the bacteria from autophagy-dependent lysosomal degradation

After entering the host cells, Salmonella Typhimurium (STM) stays inside a modified membrane-bound compartment called Salmonella containing vacuole (SCV). The biogenesis and stability of SCV are crucial for the intracellular proliferation of Salmonella. Our research has provided a novel mechanistic view on the role of a bacterial porin OmpA in maintaining the stability of SCV. We found that the deletion of OmpA forces the bacteria to escape from the SCV during the immediate early stage of infection. In the absence of OmpA, the bacteria failed to retain the LAMP-1 and came into the host cells cytosol. Subsequently, the cytosolic population of STM{Delta} ompA activated the host autophagy machinery after colocalizing with syntaxin 17 and LC3B. The autophagosomes carrying STM{Delta} ompA were targeted to the lysosomes for degradation. Inhibition of autophagy pathway using bafilomycin A1 restored the intracellular proliferation of STM{Delta} ompA. We further showed that the four extracellular loops of OmpA played a crucial role in holding the LAMP-1 pool around the SCV. We have altered the extracellular loop sequences of Salmonella OmpA by site-directed mutagenesis and observed that the bacteria failed to maintain the LAMP-1 pool around the SCV, which finally resulted in their release into the cytosol of the host macrophages. Surprisingly, the cytosolic population of Salmonella having mutations in the extracellular loops of OmpA didnt activate the lysosomal degradation pathway like STM{Delta} ompA, which helped them to survive within the murine macrophages. In summary, our study revealed an OmpA dependent novel strategy utilized by Salmonella to combat host autophagy by promoting the stability of SCV.

microbiology↗