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Define Microbiology
It is the study of micro-organisms-tiny living organisms that are not visible to the naked eye
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List some fungi
Moulds, yeasts, large fungi
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List some bacteria
Salmonella, e.coli
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List viruses
Those that cause colds and flus
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What is a parasite?
Feeds on living matter
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What is a saprophyte?
Feeds on dead matter
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What is a psychrophille?
A micro-organism that thrives at low temp -5 to 20
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Mesophiles?
Thrive at 20-45c
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Thermophiles?
Thrive at 45-75c
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Pathogens?
Disease causing bacteria
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Anaerobic?
Don't require oxygen
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How do microbes feed on food?
- Secrete enzymes onto their food source
- Breaks food down into simple compounds
- Simple compounds are absorbed through cell wall
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Describe bacteria?
- Microscopic unicellular organisms
- Found everywhere
- Pathogenic or non-pathogenic
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Structure of bacteria cell?
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Structure of bacteria cell simplified version
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Reproduction of bacteria
- Assexually by binary fission
- Produces genetically identical offspring
- Short lifecycle-reproduce every 20 mins
- New mutations spread very quickly
- Rapid growth stops as bacteria compete for food,oxygen,moisture and space
- Mature bacterial cell duplicates its nuclear material
- Remaining cell divides forming 2 cells
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Diagram of bacteria reproduction
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Spore forming bacteria
If conditions become unfavourable for bacterial growth, some bacteria form spores
The spores that develop within a bacterial cell are called endospores
Endopores grow tough wall around it
Can stay dormant for years until conditions are ok for growth
Bacilli and clostridia have the ability to form spores, which are highly resistant to heat,cold and disinfectants
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Diagram of spore formation
pg 126
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Toxins
Some bacteria produce waste called toxins
Toxins can cause food poisoning, endo or exotoxins
- Exotoxins:
- Produced OUTSIDE bacterial cell
- Before and after food is eat-responsible for toxic food poisoning
- Clostridium botulinum
- Botulinum cook at 121c for 4-6 mins kills of the bacteria
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Endotoxins
Produced in bacterial cells
Released when the cells die
Salmonella and listeria -responsible for toxic food poisoning
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Salmonella effects
Fever, diarrhoea,vomming, cramps, onset 12-72 hours after eating food, lasts 3 to days
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Classification of bacteria
- Shape:
- Spherical-cocci
- Squiggly-sprilla
- Rod-bacillus
- Gram staining:
- Positive
- Negative
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Characteristics of bacteria
- Positive:
- One cell thick
- No flagella
- Spore forming
- Low resistance to antibiotics eg streptococci-throat
- Negative:
- Cell wall is 2 thin layers
- Has flagellae
- Non-spore forming
- high resistance to antibiotics
- Salmonella
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