Browsing by Author "León-Quezada RI"

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    A large chromosomal inversion affects antimicrobial sensitivity of Escherichia coli to sodium deoxycholate
    (Microbiology Society, 2022-08-12) Le VVH; León-Quezada RI; Biggs PJ; Rakonjac J
    Resistance to antimicrobials is normally caused by mutations in the drug targets or genes involved in antimicrobial activation or expulsion. Here we show that an Escherichia coli strain, named DOC14, selected for increased resistance to the bile salt sodium deoxycholate, has no mutations in any ORF, but instead has a 2.1 Mb chromosomal inversion. The breakpoints of the inversion are two inverted copies of an IS5 element. Besides lowering deoxycholate susceptibility, the IS5-mediated chromosomal inversion in the DOC14 mutant was found to increase bacterial survival upon exposure to ampicillin and vancomycin, and sensitize the cell to ciprofloxacin and meropenem, but does not affect bacterial growth or cell morphology in a rich medium in the absence of antibacterial molecules. Overall, our findings support the notion that a large chromosomal inversion can benefit bacterial cells under certain conditions, contributing to genetic variability available for selection during evolution. The DOC14 mutant paired with its isogenic parental strain form a useful model as bacterial ancestors in evolution experiments to study how a large chromosomal inversion influences the evolutionary trajectory in response to various environmental stressors.
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    A Single-Plasmid Inducible-Replication System for High-Yield Production of Short Ff (f1, M13 or fd)-Phage-Derived Nanorods
    (John Wiley and Sons Ltd., 2025-04-01) León-Quezada RI; Miró MG; Khanum S; Sutherland-Smith AJ; Gold VAM; Rakonjac J
    Ff (f1, M13 or fd) filamentous phages have been used for myriad applications including phage display, assembly of nanostructures and as carriers of agents used for diagnostic and therapeutic purposes. Recently, short Ff phage-derived functionalised nanorods have emerged as a superior alternative to full-length filamentous phages for applications from lateral flow assays to cell- and tissue-targeting. Their advantages, such as shorter length and the lack of antibiotic resistance genes, make them particularly promising for expanding the current scope of Ff bionanotechnology and biomedical applications. Limitations to the widespread use of Ff-derived nanorods include a requirement for two plasmids and the relatively low production efficiency. This is due to the presence of only the positive Ff origin of replication, allowing replication of only the positive strand. Here we describe a single-plasmid negative origin-containing inducible-replication system for nanorod production. These improvements simplify and increase nanorod production by two orders of magnitude compared with the constitutive positive origin-only production system. The high concentration of nanorods allows formation of higher-order structures, such as stacks and rafts, as imaged by transmission electron microscopy. In summary, our system will facilitate production and expand the applications of Ff-derived biological nanorods.
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    Cryo-electron microscopy of the f1 filamentous phage reveals a new paradigm in viral infection and assembly
    (2022-11-04) Conners R; León-Quezada RI; McLaren M; Bennett NJ; Daum B; Rakonjac J; Gold VAM