Dashti, Khadijah Mohammed;
(2023)
Natural antibiotic discovery.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
Currently, there is a decline in the discovery of new antibiotics. Several important habitats that have yet to be fully exploited for antibioticproducing bacteria include water and the anterior nares. Therefore, antibiotic-producing bacteria isolated from these two environments were evaluated for antibiotic production, and using ribosome engineering, their activity was further enhanced. Five NW Pseudomonas sp. strains isolated from water were tested for antimicrobial activity against multidrug-resistant bacteria. The five strains were grown under various conditions, by which the growth medium significantly influenced the production of antimicrobials (p-value <0.001). All five strains were inhibitory to several indicator bacterium however, Pseudomonas sp. strain NW27 was inhibitory to S. aureus, E. faecium and A. baumannii. Bioinformatics analysis revealed that Pseudomonas sp. strain NW27 outperforms other strains in its ability to produce a variety of novel antimicrobials, including those related to viscosin, bananamide and syringomycin. Rifampicin-resistant Pseudomonas sp. strain NW27-A1 was isolated using 10 ug/ml rifampicin and showed significantly enhanced antimicrobial activity compared to the wild-type according to agar well diffusion assays (p-value <0.001). The MIC assay showed no significant change in the MIC of Pseudomonas sp. strain NW27-A1 compared to the wild-type (0.12 mg/ml versus 1.13 mg/ml respectively, p-value= 0.200). The active compounds were extracted from IV the supernatant of Pseudomonas sp. strain NW27-A1 using acetonitrile, and 0.23% of the units were recovered with a 1.28 fold purification. Several polar, active fractions were identified by HPLC, however the least polar fraction G significantly reduced the cellular metabolism of E. faecium E1162 by 99.65%. Moreover, bioinformatic analysis of metagenomic data suggested the ability of the commensal bacterium Dolosigranulum pigrum to produce several novel bacteriocins and a novel polyketide, that can inhibit S. aureus growth in the anterior nares. The supernatant of D. pigrum ATCC 51524 did not demonstrate considerable antimicrobial activity however, production of hydrogen peroxide was one mechanism associated with the exclusion of S. aureus in the anterior nares. However, rifampicin-resistant D. pigrum DP8rif10 successfully inhibited S. aureus JE2 when collected at 30 hours post-inoculation. Pseudomonas sp. strain NW27-A1 and D. pigrum DP8rif10 therefore offer a potential source of novel therapeutic approaches in the future.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Natural antibiotic discovery |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2023. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences > Eastman Dental Institute |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10168254 |
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