Biology subjects

Bhunia, A. K.

Publications and source records attributed to Bhunia, A. K..

3 recordsLinked to original sources

bioRxiv2026

Genomic diversity, antibiotic resistance, and maturation-dependent adhesion of F18 enterotoxigenic Escherichia coli strains in porcine intestinal cells

Enterotoxigenic Escherichia coli (ETEC) strains expressing F4 and F18 fimbriae are major causes of neonatal and post-weaning diarrhea in swine. Although epithelial maturation influences susceptibility in vivo, its impact on ETEC-host interactions remains poorly defined. This study characterizes emerging F18 ETEC isolates using a differentiated porcine intestinal cell model. Three F18 strains (3EC1, 27EC1, 3247EC), a porcine F4 strain, and human ETEC H10407 were analyzed by comparative genomics for virulence factors, toxin genes, and antimicrobial resistance determinants. Adhesion assays were performed using IPEC-1, IPEC-J2, and Caco-2 cells conditioned to Early (6 days post-confluence, DPC), Mid (9 DPC), and Late (16 DPC) maturation states. Transcription of F18-binding receptors (FUT1, FUT2) was quantified by RT-qPCR. IPEC-1 cells exhibited significantly higher FUT1 and FUT2 expression than IPEC-J2, corresponding to approximately two-fold stronger adhesion by most F18 isolates. Strain 3EC1 showed a distinct adhesion peak at 9 DPC, approaching F4 levels, while F4 and H10407 consistently displayed the highest adhesion across all models. Genomic analyses revealed substantial heterogeneity among F18 strains in fimbrial loci, flagellin, lipopolysaccharide biosynthesis, and antimicrobial resistance. Strain 3EC1 uniquely carried stx2e, and non-classical EAST1 variants were detected in 3EC1 and 3247EC. All F18 isolates encoded hlyE and were {beta}-hemolytic; 3247EC harbored 28 antimicrobial resistance genes. The IPEC-1/IPEC-J2 maturation stages recapitulate age-dependent susceptibility to ETEC, likely driven by FUT1/2 expression levels. The combination of strong adhesion, stx2e, and extensive antimicrobial resistance in F18 strains underscores their evolving virulence and supports this model as a refined platform for studying porcine ETEC pathogenesis. ImportanceETEC remains a leading cause of neonatal and post-weaning diarrhea in swine, yet the biological basis for age-dependent susceptibility is not fully understood. This study demonstrates that maturation of porcine intestinal epithelial cells strongly influences F18 ETEC adhesion, driven in part by developmental regulation of the F18-binding receptors FUT1 and FUT2. By integrating comparative genomics with a physiologically relevant in vitro maturation model, we reveal substantial diversity in virulence and resistance among F18 strains, including strong adhesion capacity, stx2e, and extensive antimicrobial resistance in strain 3EC1. These findings highlight the evolution of ETEC toward increased persistence and pathogenic potential in swine populations. The interaction between the maturation-dependent IPEC-1 and IPEC-J2 cell lines and ETEC offers a valuable tool for evaluating intervention strategies to reduce weaning piglet susceptibility to ETEC infection.

microbiology↗

bioRxiv2026

A putative GtrB-like glycosyltransferase modulates cation-dependent BCP8-2 phage infection and cell surface structure in Bacillus cereus

Bacillus cereus is a foodborne pathogen of growing concern due to its persistence and antimicrobial resistance. To identify host determinants influencing susceptibility to phage BCP8-2, a mini-Tn10 transposon mutant library of B. cereus ATCC 14579 was constructed and screened for altered phage susceptibility. A mutant (BC2012) showing partial resistance carried an insertion in BC_RS27090 (previously BC_5432), encoding a putative GtrB-like bactoprenol glycosyltransferase. Complementation restored phage sensitivity, confirming its functional involvement. Adsorption and efficiency-of-plating assays revealed significantly reduced phage binding and infectivity in the mutant, particularly under cation-rich conditions. Microscopy showed altered surface morphology with thinner, smoother cell walls. These data indicate that gtrB affects surface properties essential for cation-dependent phage adsorption and infection and provide a foundation for future studies on the role of surface glycosylation and ionic interactions in Gram-positive phage biology. ImportancePathogenic Bacillus cereus is resilient across diverse environments and produces diverse toxins linked to foodborne outbreaks. Bacteriophages provide an effective strategy to control B. cereus; however, molecular targets of phage-host interaction are poorly understood, limiting the effective phage-based control. Current study addresses this gap by identifying a putative bactoprenol glycosyltransferase (GtrB), a vital factor in phage BCP8-2 susceptibility. Data obtained highlights partial reduction of phage infection in the gtrB mutant, demonstrating that precise glycosylation is essential for effective phage binding and entry. Our findings provide significant insights for advancing phage therapy, antibiotic resistance, and B. cereus biocontrol in food and clinical settings.

microbiology↗

bioRxiv2023

Listeria adhesion protein orchestrates caveolae-mediated apical junctional remodeling of epithelial barrier for L. monocytogenes translocation

The cellular junctional architecture remodeling by LAP-Hsp60 interaction for L. monocytogenes (Lm) passage through the epithelial barrier is incompletely understood. Here, using the gerbil model, permissive to internalin (Inl) A/B-mediated pathways like in humans, we demonstrate that Lm crosses the intestinal villi at 48 h post-infection. In contrast, the single isogenic (lap[boxh] or {Delta}inlA) or double (lap[boxh]{Delta}inlA) mutant strains show significant defects. LAP promotes Lm translocation via endocytosis of cell-cell junctional complex in enterocytes that do not display luminal E-cadherin. In comparison, InlA-mediated transcytosis occurs in enterocytes displaying apical E-cadherin during cell extrusion and mucus expulsion from goblet cells. LAP hijacks caveolar endocytosis to traffic integral junctional proteins to the early and recycling endosomes. Pharmacological inhibition in a cell line and genetic knock-out of caveolin-1 in mice prevents LAP-induced intestinal permeability, junctional endocytosis, and Lm translocation. Furthermore, LAP-Hsp60-dependent tight junction remodeling is also necessary for InlA access to E-cadherin for Lm intestinal barrier crossing in InlA-permissive hosts.

microbiology↗