Yong, Sheau Ting (2019) Isolation and characterization of antarctic actinobacteria, bacteria and fungi with antimicrobial activities. Doctoral thesis, Universiti Malaysia Sabah.
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Abstract
Antimicrobial resistance (AMR) is a serious health problem worldwide. The escalating prevalence of AMR is driving the need for new antimicrobial drugs. Exploration of extreme environments such as Antarctica may give us hope to discover promising drug candidates. This study aimed to discover Antarctic spore-forming soil microorganisms that produce novel antimicrobial compounds. The microbial isolation was carried out using a combination of low- and high-nutrient isolation agar media. A total of 90 strains were isolated from two soil samples, which were further clustered into 19 groups at a similarity of 60% using random amplified polymorphic DNA fingerprinting (RAPD) fingerprinting technique. Antimicrobial activities of the isolates were tested against 13 Gram-positive and -negative bacteria, and strain Im33 was chosen for further characterization due to its capability to inhibit all bacteria. It was described on the basis of morphological, physiological and molecular phylogenetic analyses, as well as carbon utilization and antimicrobial capabilities, along with strains E22 and INACH3013. They were identified as Talaromyces, Penicillium and Streptomyces spp. respectively based on 16S rDNA, 18S rDNA or internal transcribed spacer (ITS) sequences. The strains were capable of producing enzymes to degrade a wide variety of carbon sources, suggesting that they might play a role in the nutrient cycling of Antarctic terrestrial ecosystem in order to obtain nutrients for survival and growth. Both strains Im33 and E22 showed high levels of resistance to cycloheximide, which could probably be a defence mechanism that confers them a competitive advantage over cycloheximide-sensitive species in a nutrient scarce environment. Strain INACH3013 might have a narrow spectrum β-lactamase or a different mechanism of resistance, given that it was susceptible to ampicillin but not to other β-lactam antibiotics. The inhibitory effect of strains Im33, E22 and INACH3013 against multiple Gram-positive and Gram-negative bacteria indicated that they produce broad-spectrum antimicrobial compounds. The antimicrobial compounds synthesized by strain Im33 were pH-stable, thermostable, non-polar and non-toxic, which might be good candidates for drug development. The estimated genome size of strain INACH3013 is 9,357,559 bp with 70.5% G+C content. A total of 8,551 coding sequences (CDSs) in 432 subsystems were annotated by the Rapid Annotation using Subsystems Technology (RAST) server. The secondary metabolite biosynthetic potential of strain INACH3013 was assessed using the antibiotics and Secondary Metabolites Analysis SHell (antiSMASH). Thirty-two biosynthetic gene clusters (BGCs) were predicted to be involved in the production of 1 bacteriocin-terpene hybrid, 2 bacteriocins, 8 NRPSs, 2 T1PKSs, 1 T2PKS, 1 T3PKS, 1 ectoine, 1 lantipeptide, 1 lassopeptide, 2 melanins, 2 siderophores, 2 terpenes, 1 T1PKS-NRPS hybrid, 1 bacteriocin-T1PKS hybrid, 1 T1PKS-butyrolactone hybrid, 1 T2PKS-T1PKS hybrid, 1 lantipeptide-terpene hybrid and 3 secondary metabolite-related proteins that did not fit into any category. Fifteen clusters that displayed low similarities (<40%) to known BGCs in other strains are most probably species specific and might encode metabolites with previously unreported novel chemical structures and biological activities. Eight clusters that showed no relatedness to any known BGCs might synthesize potentially unknown natural products, or their compounds could only be partially predicted from the genes’ organization. These preliminary findings support that Antarctic spore-forming microorganisms are a great source of novel bioactive metabolites with biotechnological and pharmaceutical potentials.
| Item Type: | Thesis (Doctoral) |
|---|---|
| Keyword: | Antimicrobial resistance, Antarctic soil microorganisms, Spore-forming microorganisms, Novel antimicrobial compounds, Microbial isolation, Broad-spectrum antimicrobials, TalaromycesAntimicrobial resistance, Antarctic soil microorganisms, Spore-forming microorganisms, Novel antimicrobial compounds, Microbial isolation, Broad-spectrum antimicrobials, Talaromyces |
| Subjects: | Q Science > QR Microbiology > QR1-502 Microbiology > QR1-74.5 General |
| Department: | INSTITUTE > Biotechnology Research Institute (BRI) |
| Depositing User: | DG MASNIAH AHMAD - |
| Date Deposited: | 20 Jan 2025 13:47 |
| Last Modified: | 20 Jan 2025 13:47 |
| URI: | https://eprints.ums.edu.my/id/eprint/42655 |
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