Biology subjects

Khan, C. M. A.

Publications and source records attributed to Khan, C. M. A..

3 recordsLinked to original sources

bioRxiv2024

Essential Roles of RodA Peptidoglycan Polymerase and PBP2 Transpeptidase in Expression of Cell Wall-Spanning Supramolecular Organelles and Modulating Salmonella Virulence

The increased spread of multidrug-resistant bacteria no longer sensitive to commonly used antibiotics poses a major threat to human health. The search for potential new drug targets is critical in disease control and prevention. Whilst several components of the cell wall synthesis machinery are already targeted by beta-lactam antibiotics, other elements of this machinery present opportunities for novel drug targets. Landmark studies revealed RodA exhibits peptidoglycan polymerase activity in Bacillus subtilis and Escherichia coli, highlighting RodA as a prime for the next generation of antimicrobial drugs. However, the role of RodA in virulence remains unexplored. Through targeted mutagenesis, virulence gene reporter assays, and phenotypic screening, we demonstrate that the presence of RodA or PBP2, is intrinsically linked to the regulation of virulence gene expression in Salmonella. Specifically, deletion of either of these components causes both disruption in cell morphology and a complete downregulation in major cell invasion-associated virulence factors in vitro, and attenuated virulence in vivo. Significantly, this study highlights the importance of RodA and PBP2 in both the biology and virulence of an important bacterial pathogen, identifying them as promising targets for developing new antibiotics.

microbiology↗

bioRxiv2024

Colicin Receptor CirA Enhances Salmonella Typhimuriums Resistance to Colicin Ib in the Absence of the Cognate Immunity Protein

Intestinal microbiota play a central role in colonisation resistance providing a fundamental barrier to infection to enteric pathogens. An important mechanism of colonisation resistance involves the production of antimicrobial peptides, such as colicins. Pore-forming colicins, synthesised by Escherichia coli (E. coli) strains, target competing bacteria in their environmental niche, whilst the producing cells are safeguarded by specific immunity proteins. Notably, non-typhoidal Salmonella Typhimurium strains can produce a narrow-spectrum protein toxin colicin IB (ColIb) providing a competitive edge against susceptible Enterobacteriaceae strains. However, the multi-drug resistant and systemically invasive iNTS (invasive non-Typhoidal Salmonella) S. Typhimurium D23580 strain poses an interesting case. The strain lacks colicin Ib production and the corresponding immunity protein, but its potential vulnerability in a colicin-rich gastrointestinal milieu remains uninvestigated. In this study, S. Typhimurium D23580 exhibited resistance to colicin Ib under tested conditions, despite the absence of the immunity gene imm. Intriguingly, in colicin Ib-producing S. Typhimurium strains, the imm gene appeared functionally redundant in contrast to our current understanding. ColIb binds to the outer membrane protein CirA and is translocated to the inner membrane where it forms a pore in sensitive bacteria dissipating the electrochemical potential. Through a series of experimental approaches, including the use of Escherichia coli and S. Typhimurium cirA deletion mutants, promoter-swap techniques, and gene complementation, we identified that the colicin resistance phenotype in S. Typhimurium was partly attributable to the CirA receptor. This finding suggests a complex interplay in the microbial resistance to colicins, highlighting the intricacies of microbial interactions within the gastrointestinal environment.

microbiology↗

bioRxiv2021

Conjunctival epithelial cells resist productive SARS-CoV-2 infection

Although tropism of SARS-CoV-2 for respiratory tract epithelial cells is well established, an open question is whether the conjunctival epithelium is also a target for SARS-CoV-2. Conjunctival epithelial cells, which express viral entry receptors ACE2 and TMPRSS2, constitute the largest exposed epithelium of the ocular surface tissue, and may represent a relevant viral entry route. To address this question, we generated an organotypic air-liquid-interface model of conjunctival epithelium, composed of progenitor, basal and superficial epithelial cells and fibroblasts, which could be maintained successfully up to day 75 of differentiation. Using single-cell RNA Seq, with complementary imaging and virological assays, we observed that while all conjunctival cell types were permissive to SARS-CoV-2 genome expression, a productive infection did not ensue. The early innate immune response to SARS-CoV-2 infection in conjunctival cells was characterised by a robust autocrine and paracrine NF-K{beta} activity, without activation of antiviral interferon signalling. Collectively, these data enrich our understanding of SARS-CoV-2 infection at the human ocular surface, with potential implications for the design of preventive strategies and conjunctival transplants.

cell biology↗