Exploitation of Microorganisms
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- Created by: amazingemilyjones
- Created on: 15-04-19 14:33
Exploitation of Microorganisms
Exploitation of Microorganisms
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Bioremediation
- The use of microorganisms to consume and break down environmental pollutants, in order to clean a polluted site
- Microbes can be used to tackle many contemporary environmental issues:
- Heavy metal contamination
- Oil spills
- Pesticides and xenobiotics
- Plastic waste
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Bioremediation: Heavy Metals
- Major form of mercury in atomosphere: Hg0 - vapour
- Oxidised to mercuric ion: Hg2+
- Enters into aquatic environments - adsorbs to particulate matter
- Metabolism by microorganisms results in methylation: CH3Hg+
- Methyl-mercury binds to sulfhydryl groups (primarily cysteine amino acid residues). Acts as a molecular mimic to methionine so is distributed throughout the body. 100 times more toxic than elemental mercury
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Bioremediation: Heavy Metals
- Several bacterial species can enzymatically biotransform methyl mercury or divalent mercury into less toxic elemental mercury
- Enzymatic mercuric reductase
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Bioremediation: Heavy Metals
- Other species sequester heavy metals by secreting siderophores
- Siderophores are biological chelators which are normally used to acquire iron from the environment. Have an extremely high affinity for metals and so can help improve removal from soil
Bioremediation: Oil Spills
- HydrocarbonsL: rich source of organic material for microbial growth
- Bulk storage - microbial growth is not desirable
- Oil-oxidising bacteria oil --> carbon dioxide
- Oil-oxidising bacteria (Alcanivorax borkumensis) develop rapidly on slicks/films and eventually decompose the oikl
- Bioremediation can be accelerated by the addition of nutrients (fertilisers) and oxygen. Ongoing debate on the use of dispersant agents - makes oil sink so less oxygen available to break down
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Bioremediation: Pesticides
- One of the most widely used chemicals - 2 million tonnes estimated to be used each year
- If they can be attacked by microorganisms:
- eventually disappear from the soil
- prevent toxic accumulations
- save the bees
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Bioremediation: Polychorinated Biphenyls (PCBs)
- Used as industrial coolants or insulators
- Spills or leakage into the environment
- Eventually reaches groundwater
- Toxic, persistent and bio-accumulative
- Reductive de-halogenation - PCBs can be decomposed by some microorganisms under anoxic conditions
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Bioremediation: Plastics
- 40 billion kilograms produced per year
- Half discarded in land fills - remain unaltered for decades
- Biodegradable platics
- Photobiodegradable
- structure altered by sunlight (UV)
- more amenable to microbial attack
- Starch-based plastic
- starch used to link short fragments of a second biodegradable polymer
- Photobiodegradable
- Japanese researches have isolated species living on plastic waste (Ideonella sakaiensis) which can degrade PET into ethylene glycol and terapthalic acid - could be used in landfills to speed up decomposition of existing waste
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Antibiotics
- Chemicals produced by microorganisms that kill or inhibit growth of other microorganisms
- With the advent of synthetic synthesis the definition now includes substances partly or wholly produced through chemical synthesis
- 1928 - original organism for the production of penicillin, Penicillum notatum, isolated as a chance contaminant (Alexander Fleming)
- 1939 - Howard Florey and colleagues isolated the active ingredient from the mould, developed a powder and conducted the the first clinical trial
- Only small quantities of the drug could be produced
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Antibiotics
- 1941 - Andrew J. Moyer, found that culturing the organism in a specific broth, along with controlled aeration, resulted in much higher yields
- Higher yielding strain, P.chrysogenum, isolated from an infected cantaloupe melon in U.S., could be used in a large scale fermentation process - key advance
- Strain selection - fundamental geature of the use of microorganisms in biotechnology
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Antibiotics
- Some antibiotics produced commercially
- Streptomycetes produce >2/3 of clinically used antibiotics
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Toxins
- The properties of some exotoxins allow them to be used medically
- Botulinum Toxin
- Clostridium botulinum - normally inhabits soil and water
- May contaminate foods before harvest or slaughter
- Botulism
- Severe food poisoning caused by the consumption of food containing the exotoxin produced by C.botulinum
- Most potent biological toxin known - attacks neural synapses
- Causes hypotonia (muscle relaxation), paralysis, respiratory failure and death
- Cosmetic industry: minute amounts - muscle relaxant (botox)
- Medically: injected into patients suffering from dystonia - muscle spasms cause twisting and repetitive movements or poor posture
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Enzymes
- Many pharmaceuticals are produced by haemolytic streptococcal strains
- Streprokinase - Thrombolysis
- Mammalian blood will clot if allowed to stand
- Further standing it may dissolve as a result of an enzyme - plasmin
- Plasmin usually present as inactive precursor - plasminogen
- Administered intravenously to treat deep vein thrombosis or myocardial infarction
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Enzymes
- Streptodornase
- Liquefies puss - breaks down deoxyribonucleoprotein and DNA
- Streptodornase and Streptokinase together used topically to liquefy blood clots and puss in wounds (Varidase)
- L-asparaginase
- Produced by many bacteria, e.g. Escherichia coli
- Employed in cancer chemotherapy
- L-asparagine is an essential requirement of some tumours
- L-asparagine - selective, targeted treatment
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Dextrans
- Polysaccharides produced commercially used as a plasma substitute
- Lactic acid bacteria (Leuconostoc) can produce dextrans (from sucrose)
- Glucose polymer (1,6alpha-linkages)
- High/variable molecular weight
- Dextran produced depends on the strain used for production
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Amino Acids
- Pharmaceutical use: ingredients of infusion solutions for parenteral nutritional food supplements
- Commercial use: food supplements
- Produced commercially in fermentation processes
- Brevibacterium flavum
- Corynebacterium glutamicum
- Both produce glutamic acid by a fermentation process
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Vitamins
- Most made commercially through chemical synthesis
- A few are too complex to be manufactured cheaply
- Riboflavin (vitamin B2)
- Deficiency characterised by enflamed tongue, dermatitis, 'burning feet'
- Produced commercially in high yields by the mould Ashbya gossipii and the bacterium Bacillus subtilis
- Vitamin B12
- Synthesis in nature exclusively by microorgansisms, dietary needs satisified by food intake or absorption of the vitamin produced in the gut by microbes - Propionibacterium, Pseudomonas
- Deficiency - low red blood cell, nervous system, dementia
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Vaccines
- Live vaccines (attenuated)
- symptomless infection - involve immune response and infection
- Bacille Calmette-Guerin (BCG) strain causes tuberculosis in cattle not humans
- Protection against human strain - cross protection
- Killed vaccines
- do not replicate/cause infection
- Typhoid, cholera, influenza
- Component vaccines
- Hepatitis B (HBsAg)
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Insecticides
- Bacillus thuringiensis
- Crystalline inclusion - parasporal body
- Endotoxin
- Active against insect larvae (paralysis and death)
- Spores produced as dusting powder)
- GM crops contain cry genes - produce endotoxin
- Bacillus sphaericus
- Two proteins (51 and 42kDa) toxic to mosquito larvae
- Microbe introduced into waters where larvae develop
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Brewing
- Fermentable sugars and nutrients extracted from malt/sugar/hops
- Placed into a fermentation vessel and brewing yeasts added
- Ferment sugars and produces alcohol and carbon dioxide
- Top fermenting yeasts - Saccharomyces cerevisiae
- Production of ales
- Bottom fermenting yeasts - Saccharomyces carlsbergensis
- Production of lager
- Yeasts broken down - full of B vitamins and proteins
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Probiotics
- Live microorganisms which, when administered in adequate amounts, confer a health benefit on the host
- Human intestine
- Human intestine - contains 1.2kg of bacteria
- Stable ecosystem: first few months of life to old age
- Probiotics - evidence?
- The general gut microflora prevent growth of pathogenic bacteria
- Probiotics do not generally change the gut flora - must be taken daily to have any noticeable effect
- Commercial strains: Lactobacillus and Bifidobacterium
- Very profitable
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Antibiotic-Associated Diarrhoea
- Systemic use of antibiotics disrupts normal gut flora
- Clostridium difficile becomes a major pathogen
- Produces two toxins - A and B, which cause psuedomembranous colitis, toxic megacolon and mortality
- Vacomycin/metronidazole administered in combination with probiotics
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Genetic Engineering
- Ralstonia metallidurans
- Resistant to an array of heavy metals (zinc, cadmium, lead copper)
- Able to breakdown a variety of pollutants
- Recombinant strain (adding genes) used to decontaminate soils allowing re-vegetation
- Resistance is plasmid-borne and can be exported to other organisms
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Genetic Engineering
- Pharmaceuticals
- Higher yielding strains
- Probiotics
- Probiotic E.coli strain engineered to secrete an anti-HIV peptide
- Prevents HIV from entering cells
- Insecticides
- Expressing bacterial genes in plants
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Vaccines
- Live vaccines (first generation)
- Delete genes involved in disease
- Component vaccines (second generation)
- Relevant antigens expressed in bacteria, purified and administered
- DNA vaccines (third generation)
- Defined fragments of the pathogen's DNA which encode an antigen
- Cloned into a plasmid and injected
- DNA taken up by animal cell, transcribed and translated
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Mammalian Genes
- Human proteins have high pharmaceutical value
- Present in small amounts in normal tissue - costly to purify
- Genetically engineered micoorganisms to produce these proteins
- Insulin --> diabetes
- Blood clotting factors --> haemophilia
- Interferons --> anti-cancer agent
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