Understanding the biochemical warfare in the nests of fungus-growing ants

Hamilton, Jacob (2022) Understanding the biochemical warfare in the nests of fungus-growing ants. Doctoral thesis, University of East Anglia.

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Antimicrobial resistance (AMR) is a growing health concern, estimated to cause 1.27 million deaths worldwide in 2019. New antimicrobials are required to improve treatment options that evade resistance. However, the rediscovery of previously reported antimicrobials has become a common occurrence. One way to reduce the risk of rediscovery is to search for bacteria producing natural products in underexplored environmental niches. Fungus-growing ants cultivate a fungal garden, consumed by the colony as a food source. The specialised pathogen, Escovopsis, can invade these fungal gardens and, if left uncontrolled, cause colony collapse. To prevent this, fungus-growing ants have formed a symbiotic relationship with antimicrobial-producing actinomycete bacteria, most notably Pseudonocardia. Despite evolving this relationship approximately 50 million years ago, fungus-growing ant colonies show few AMR-associated problems.

Here, 18 actinomycetes isolated from colonies of fungus-growing ants across Africa and South America were assessed for their ability to inhibit B. subtilis, E. coli and C. albicans on 35 different growth media, and their genomes were analysed. These strains came from multiple genera, including Streptomyces, Pseudonocardia, Amycolatopsis and Jiangella. Chemical extractions of three strains, which demonstrated antimicrobial activity but did not contain an antimicrobial-encoding biosynthetic gene cluster (BGC), were performed. Initial attempts were made to purify and identify the compounds responsible for antimicrobial activity via biological activity-guided fractionation. Further, ex-conjugants of two strains were generated using CRISPR/Cas9 to disrupt BGCs potentially encoding antimicrobials, in one strain leading to the cessation of antifungal activity. Initial attempts at comparative metabolomics were performed to identify the antifungal compound.

Although no novel antimicrobial was uncovered, the analysis of the 18 actinomycete strains showed that fungus-growing ant colonies are a reservoir of unreported secondary metabolites. Further, this work demonstrated the ability of the pCRISPomyces-2 system to be applicable to environmental Streptomyces strains, allowing for further studies in these strains to be performed.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Chris White
Date Deposited: 30 Jan 2023 12:20
Last Modified: 30 Jan 2023 12:20
URI: https://ueaeprints.uea.ac.uk/id/eprint/90858

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