Identification of novel streptomyces strains with antimicrobial and antitumour activity isolated from terrestrial habitats

Al-Joubori, Ban Mundhir (2020). Identification of novel streptomyces strains with antimicrobial and antitumour activity isolated from terrestrial habitats. University of Birmingham. Ph.D.

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Streptomyces, Gram positive filamentous bacteria, are very important organisms due to their capability of producing a variety of useful secondary metabolites with many biological activities and applications such as antibiotics, anticancer drugs and antioxidants. The increase in resistant pathogens, emergence of new diseases and toxicity of drugs that are currently used makes the urgent search to find new bioactive compounds in the medical industry to be of major importance. UAE is an under explored habitat that may have the potential to harbour novel Streptomyces strains producing diverse natural products. The main aim of the study is to isolate novel Streptomyces species from terrestrial habitats. Six Streptomyces strains (CSK1, CSK3, CSW2, CSU1, CSU2 and CSG1) were found to produce antimicrobial metabolites against Escherichia coli, Staphylococcus aureus, Candida albicans, Saccharomyces cerevisiae and Escherichia coli-ESBL using the well diffusion method. Phylogenetic analysis of the 16S rRNA sequence confirmed the identification and novelty of the six isolates to the genus of Streptomyces. The cytotoxicity of the extracts was investigated on HeLa cancer cell line by MTT assay and DAPI staining where some of the isolates inhibited the growth of HeLa cells in a concentration-dependent manner and caused apoptosis observed by DNA fragmentation and chromatin condensation. Cultivating the isolates with Bacillus subtilis and N-acetylglucosamine resulted in one isolate acquiring cytotoxic activity against HeLa cells which was not observed in the monoculture. Cultivation with γ-Butyrolactone led to either enhancement or inhibition of antimicrobial and cytotoxic activity. Genomic sequencing and liquid extraction surface analysis mass spectrometry (LESA-MS) techniques were performed to identify biosynthetic genes produced by the isolates. The genome of the isolates was sequenced and a variety of biosynthetic gene clusters were predicted by antiSMASH analysis. Finally, LESA-MS was performed as a novel technique of direct sampling from the bacterial colonies. Distinct changes in mass profiles were generated between the uninduced and induced isolates which was observed as appearance, disappearance or increase of intensity in the produced peaks. The masses of the biosynthetic gene clusters produced by antiSMASH were additionally confirmed by LESA. Based on the results of this study, we conclude that these isolates are capable of producing antimicrobial and anticancer metabolites, varied and distinct biosynthetic gene clusters and they represent novel species of the genus Streptomyces.

Type of Work: Thesis (Doctorates > Ph.D.)
Award Type: Doctorates > Ph.D.
Licence: All rights reserved All rights reserved
College/Faculty: Colleges (2008 onwards) > College of Life & Environmental Sciences
School or Department: School of Biosciences
Funders: None/not applicable
Subjects: Q Science > QR Microbiology


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