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Mining Microbial Diversity
Gwynneth Matcher
Department of Biochemistry and Microbiology
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What are microorganisms?
Bacteria (Size range : 700µm - 0.2 µm)
Algae (Unicellular, filamentous)
Fungi (Unicellular, filamentous)
Protists (e.g. amoeba, Plasmodium)
Viruses
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• Estimated 100 000 to 10 000 000 000 bacteria per gram of soil
• Microorganisms produce more oxygen than trees
• Marine Viruses - ~ 1013 particles per litre of seawater
Microbial Abundance
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“Imagine walking out in the countryside and not being able to
tell a snake from a cow from a mouse from a blade of grass. That has been our level of ignorance”
~Carl Woese
With reference to microbes :
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Hug et al., 2016
• 92 bacterial phyla
• CPR phyla (purple)
- No isolated representative
- Still in the process of definition at lower taxonomic levels
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Microbial component of ecosystem functioning
• Ubiquitous
• Play key roles in biogeochemical processes
• Integral part of all ecosystems
• Identification through 16S rRNA, 18S rRNA, ITS genes
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Example of ecological studies : Eastern Cape estuaries
(Matcher et al. 2011)
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Eastern Cape estuaries
Cyanobacterium Synechococcus sp.
Pelagibacter ubique
Variovovax paradoxus Acidovorax valerianellae Caenimonas koreensis
(Matcher et al. 2011)
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Whole genome sequencing
Fragment &
sequence
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A single next gen sequencing run (Miseq platform)
20-25 million sequences (13-15 Gb of data)
generates
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Sequence results
Find overlapping sequences
Build contiguous sequences
Final contigs
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Elucidation of biosynthetic pathways
Predicted structure
Structural homologue
Siderophore
(Jiwaji et al. 2017)
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Metagenomics
• Extract DNA from all the cells in the community
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Metagenomics
• Extract DNA from all the cells in the community
• Use NGS technology to sequence the community DNA
• Bioinformatics to re-assemble the sequences from overlapping reads
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Metagenomics
• Extract DNA from all the cells in the community
• Use NGS technology to sequence the community DNA
• Bioinformatics to re-assemble the sequences from overlapping reads
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Reassembling microbial genomes from metagenomics sequence datasets
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Bioinformatic identification of biosynthetic gene clusters
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Example of commercial application :
Marine natural products research
• ~3500 km of coastline, 5 Bioregions • 12,914 recorded species (excluding microbiota) • 346 sponge and 227 tunicate species
Griffiths et al., 2010
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Sponge-microbe interactions
• Sessile marine invertebrates (Phylum: Poriphera)
• Up to 50 % of sponge body mass made up by bacteria
• Bacterial symbionts provide nutrients e.g. nitrogen, phosphates
• Bacterial symbionts produce bioactive secondary metabolites used by the sponge for chemical defence
Phorbas clathrata Tsitsikamma pedunculata Aaptos sp Tsitsikamma favus
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MARINE DRUG DISCOVERY From chemical defence to anti-cancer therapies
Tsitsikamma pedunculata Tsitsikamma favus
Mandelalides • Purified from the ascidian
Lissoclinum mandelalii (Algoa Bay) • Potent anti-cancer activity • Secondary metabolites likely
produced by microbial symbiont
Pyrroloiminoquinones • Topoisomerase
inhibitor • Anti-malarial, anti-TB
activity • Likely produced by
bacterial symbiont Tsitsikammamine A
Sikorska et al., 2012
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