Browsing by Author "Marathe, Sandhya Amol"

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Clustered regularly interspaced short palindromic repeats-cas system: diversity and regulation in enterobacteriaceae
(Taylor & Francis, 2022-08) Marathe, Sandhya Amol
Insights into the arms race between bacteria and invading mobile genetic elements have revealed the intricacies of the clustered regularly interspaced short palindromic repeats (CRISPR)-Cas system and the counter-defenses of bacteriophages. Incredible spacer diversity but significant spacer conservation among species/subspecies dictates the specificity of the CRISPR-Cas system. Researchers have exploited this feature to type/subtype the bacterial strains, devise targeted antimicrobials and regulate gene expression. This review focuses on the nuances of the CRISPR-Cas systems in Enterobacteriaceae that predominantly harbor type I-E and I-F CRISPR systems. We discuss the systems' regulation by the global regulators, H-NS, LeuO, LRP, cAMP receptor protein and other regulators in response to environmental stress. We further discuss the regulation of noncanonical functions like DNA repair pathways, biofilm formation, quorum sensing and virulence by the CRISPR-Cas system. The review comprehends multiple facets of the CRISPR-Cas system in Enterobacteriaceae including its diverse attributes, association with genetic features, regulation and gene regulatory mechanisms
Comprehensive blueprint of Salmonella genomic plasticity identifies hotspots for pathogenicity genes
(PLOS One, 2024-08) Marathe, Sandhya Amol
Understanding the dynamic evolution of Salmonella is vital for effective bacterial infection management. This study explores the role of the flexible genome, organised in regions of genomic plasticity (RGP), in shaping the pathogenicity of Salmonella lineages. Through comprehensive genomic analysis of 12,244 Salmonella spp. genomes covering 2 species, 6 subspecies, and 46 serovars, we uncover distinct integration patterns of pathogenicity-related gene clusters into RGP, challenging traditional views of gene distribution. These RGP exhibit distinct preferences for specific genomic spots, and the presence or absence of such spots across Salmonella lineages profoundly shapes strain pathogenicity. RGP preferences are guided by conserved flanking genes surrounding integration spots, implicating their involvement in regulatory networks and functional synergies with integrated gene clusters. Additionally, we emphasise the multifaceted contributions of plasmids and prophages to the pathogenicity of diverse Salmonella lineages. Overall, this study provides a comprehensive blueprint of the pathogenicity potential of Salmonella. This unique insight identifies genomic spots in nonpathogenic lineages that hold the potential for harbouring pathogenicity genes, providing a foundation for predicting future adaptations and developing targeted strategies against emerging human pathogenic strains.
The CRISPR-Cas system differentially regulates surface-attached and pellicle biofilm in salmonella enterica serovar typhimurium
(ASM Journals, 2022-06) Marathe, Sandhya Amol
The CRISPR-Cas mediated regulation of biofilm by Salmonella enterica serovar Typhimurium was investigated by deleting CRISPR-Cas components ΔcrisprI, ΔcrisprII, ΔΔcrisprI crisprII, and Δcas op. We determined that the system positively regulates surface biofilm while inhibiting pellicle biofilm formation. Results of real-time PCR suggest that the flagellar (fliC, flgK) and curli (csgA) genes were repressed in knockout strains, causing reduced surface biofilm. The mutants displayed altered pellicle biofilm architecture. They exhibited bacterial multilayers and a denser extracellular matrix with enhanced cellulose and less curli, ergo weaker pellicles than those of the wild type. The cellulose secretion was more in the knockout strains due to the upregulation of bcsC, which is necessary for cellulose export. We hypothesized that the secreted cellulose quickly integrates into the pellicle, leading to enhanced pellicular cellulose in the knockout strains. We determined that crp is upregulated in the knockout strains, thereby inhibiting the expression of csgD and, hence, also of csgA and bcsA. The conflicting upregulation of bcsC, the last gene of the bcsABZC operon, could be caused by independent regulation by the CRISPR-Cas system owing to a partial match between the CRISPR spacers and bcsC gene. The cAMP-regulated protein (CRP)-mediated regulation of the flagellar genes in the knockout strains was probably circumvented through the regulation of yddx governing the availability of the sigma factor σ28 that further regulates class 3 flagellar genes (fliC, fljB, and flgK). Additionally, the variations in the lipopolysaccharide (LPS) profile and expression of LPS-related genes (rfaC, rfbG, and rfbI) in knockout strains could also contribute to the altered pellicle architecture. Collectively, we establish that the CRISPR-Cas system differentially regulates the formation of surface-attached and pellicle biofilm.
CRISPR-Cas system positively regulates virulence of Salmonella enterica serovar Typhimurium
(Springer, 2024-10) Marathe, Sandhya Amol
Salmonella, a foodborne pathogen, possesses a type I-E clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR associated (Cas) system. We investigated the system’s role in regulating Salmonella virulence by deleting the CRISPR arrays and Cas operon.
Emerging relationship between the gut microbiota and neurodegenerative disorders
(Springer, 2024-08) Marathe, Sandhya Amol; Tare, Meghana
A growing body of evidence indicates that the multitude of organisms residing in our gut can profoundly affect our health. These organisms are loosely termed as gut microbiota and have been known to affect the function as well as the behavioral aspects of human health. Recent research shows that the microorganisms in our gut play a crucial role in determining our health and susceptibility to disease. Newly identified intricacies of connection between nervous system and gut microbiota are specially intriguing, since nervous system intersects and in a manner regulates almost every other function of the body. Interestingly, gut microbiota has been found to be affected in cases of nervous system disorders, including neurodegeneration, such as but not limited to Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and multiple sclerosis. The number of people worldwide with neurodegenerative disorders grows yearly, but effective treatments with few side effects remain limited. There is a new avenue of translational research, which evaluates the gut-brain-microbiome axis for management and therapeutic ideas for neurodegenerative disorders. It is therefore important to understand the newer intervention techniques using microbiota, which can be employed for holistic cure of neurodegenerative disorders. This chapter encompasses a comprehensive review of the relationship between gut microbiota in the context of specific neurodegenerative disorders.
Formulating ternary inclusion complex of sorafenib tosylate using β-cyclodextrin and hydrophilic polymers: physicochemical characterization and in vitro assessment
(Springer, 2022-09) Marathe, Sandhya Amol; Singhvi, Gautam
Sorafenib tosylate (SFNT) is the first-line drug for hepatocellular carcinoma. It exhibits poor solubility leading to low oral bioavailability subsequently requiring intake of large quantities of drug to exhibit desired efficacy. The present investigation was aimed at enhancing the solubility and dissolution rate of SFNT using complexation method. The binary inclusion complex was prepared with β-cyclodextrin (β-CD). The molecular docking studies confirmed the hosting of SFNT into hydrophobic cavity of β-CD, while the phase solubility studies revealed the stoichiometry of complexation with a stability constant of 735.8 M−1. The ternary complex was prepared by combining the SFNT-β-CD complex with PEG-6000 and HPMC polymers. The results from ATR-IR studies revealed no interaction between drug and excipients. The decreased intensities in ATR-IR peaks and changes in chemical shifts from NMR of SFNT in complexes indicate the possibility of SFNT hosting into the hydrophobic cavity of β-CD. The disappearance of SFNT peak in DSC and XRD studies revealed the amorphization upon complexation. The ternary complexes exhibited improved in vitro solubility (17.54 µg/mL) compared to pure SFNT (0.19 µg/mL) and binary inclusion complex (1.52 µg/mL). The dissolution profile of ternary inclusion complex in 0.1 N HCl was significantly higher compared to binary inclusion complex and pure drug. In cytotoxicity studies, the ternary inclusion complex has shown remarkable effect than the binary inclusion complex and pure drug on HepG2 cell lines.