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What is a eukaryote cell?
Type of cell that makes up the tissues of the human body, animals, protozoa, yeasts and plants.
What is a prokaryote cell?
Bacteria and Archaea
Do Viruses contain cells?
What is the most significant difference between prokaryote and eukaryote cells?
Prokaryote cells do not have an organised, recognisable nucleus. DNA is a long single chromosome with no membrane around it.
Give examples of microbiology in food and beverages.
Mushrooms, marmite, bread, cheese, yoghurt, butter, chocolate, beer, wine. Fermentation reactions.
What is meant by bioremediation, give an example.
Microbes used to clean up the environment. Treatment of sewage by breakdown of organic matter. Breakdown toxic substances in oil spills.
What is meant by agricultural microbiology, give an example.
Microbes in soil decompose and recycle nutrients to plants. Eg nitrogen.
What are biotechnology products?
They use microbial action in their production. eg. antibiotics, ethanol, amino acids, nappies, cellulose in headphones, enzymes in laundry powder.
What is binomial nomenclature? ("two names")
- Naming of an organism.
- First word is Genus
- Second word is species
What are the units of measurements commonly used to describe microorganisms?
- Micrometer - common for bacteria
- Nanomter - common for virus - need electron microscope
some protozoa can just be seen with the eye.
What is a bacterial colony?
Visible clump of bacterial cells that have grown from one cell via repeated divisions of cells. contain identical cells.
Describe the features of bacteria.
- Have no nucleus
- DNA is a single continuous loop
- Have no membrane bound organelles
- Divide by binary fission (not mitosis)
Referring to bacteria, state a main function for capsule.
- Protects pathogenic bacteria from phagocytosis.
- Aids in attachment to surfaces, eg. teeth.
Referring to bacteria, state a main function for cell wall.
- Maintain shape of cell.
- Protects from environmental factors, such as osmotic pressure.
Referring to bacteria, state a main function for cell membrane.
- (Plasma membrane).
- Allows some molecules to pass through but prevents others from entering or leaving
Referring to bacteria, state a main function for cytoplasm
medium for many metabolic/biochemical reactions of the cell.
Referring to bacteria, state a main function for ribosome.
Site of protein synthesis.
Referring to bacteria, state a main function for chromosome.
- Contains all the genetic info for the cells metabolism.
- single long and continuous circular molecule of DNA
Referring to bacteria, state a main function for Plasmid.
- A circular extra-chromosomal structure containing additional genes.
- Some carry genes for antibiotic resistance.
- Not used in normal function.
- Can transfer from cell to cell
Referring to bacteria, state a main function for Pili (fimbriae)
- Help cells attach to surfaces.
- Transfer genetic information between certain cells. Plasmid can get through hollow tubes.
- Not a means of locomotion.
- gram negative.
Referring to bacteria, state a main function for flagellum
- Help bacteria move towards favourable environment.
- Assist in attachment to surfaces.
Referring to bacteria, state a main function for endospore
- Very resistant to heating and drying.
- Formed in unfavourable conditions.
- Not reproductive structure, one spore makes one bacterial cell.
What is the use of the gram stain?
The first step in species identification
What is the difference between Gram positive and Gram negative?
- Gram positive cells have more layers of peptidoglycan in their cell walls.
- Gram positive cells retain the crystal violet dye and appear purple/dark blue
What colour do gram negative cells stain?
Pink, due to safranin counterstain.
Define opportunistic bacteria.
Normally harmless bacteria that can cause problems if they go into the wrong site. eg E. coli
What does bacillus look like?
What does diplococci look like?
8 Two circles
What does streptococci look like?
A chain of circles
What does staphylococci look like?
A cluster of circules
What does spirochaete look like?
- A. Capsule
- B. Cell wall
- C. Plasma membrane
- D. Pili/Fimbriae
- E. Flagella
- F. Plasmid
- G. DNA/Chromosome
- H. Ribosome
- I. Cytoplasm
What type of cells are fungi made of?
Why can yeasts and moulds grow in a wide range of habitats?
- They can grow in a wide temp range, -6oC to 50oC. (best 20-35)
- Wide pH range, 2.2 to 9.6. (best acidic, 5.0 and lower)
Why are fungi heterotrophs?
They do not synthesise their own food. They secrete enzymes (exoenzymes) that degrade organic material into small molecules that can be absorbed.
What are yeasts?
- Single cell fungi.
- 3-5 μm.
- reproduce through binary fission or budding.
What are moulds?
- Multi cell, thread like fungi.
- A single filament (thread) is known as a hypha which develop from spores
- A collection of hyphae is known as mycelium
- Rotten fruit - white = mycelium, blue/green = spores.
What are dimorphic fungi?
They can grow as yeasts and moulds. eg thrush
How are fungi classified?
- According to the types of spores produced.
- They can reproduce sexually and asexually.
What is a superficial fungal mycosis?
Occur on outer parts of the body. eg ringworm
What is a systemic fungal mycosis?
Affect tissues and organs deep within the body. eg aspergillosis.
What are opportunistic micoses?
Caused by fungi that are normally harmless.
What type of cells are protozoa?
- Eukaryote cells.
- single celled animals - based on the way they take in their food.
- they require a moist environment.
- They eat bacteria and fungi
Do protozoa contain a rigid cell wall?
No, they get their shape from what lies below the cell wall.
What are the main distinguishing features of protozoa?
- classified by how they move.
- Flagella - giardia
- Cilia - Paramecium
- Pseudopodia - false feet - changes in flexability of cell membrane allowing cytoplasm to flow - amoeba
- No motile stage - parasitic - malaria
What are some protozoan diseases in humans?
- Malaria (plasmodium) - non motile
- toxoplasmosis - flue like, from cats
- giardia and cryptosporidium - water borne
What are the differences between viruses and cellular organisms? (5 points)
- Viruses have DNA or RNA, nor both
- virus structure is different to a cell. has capsid protein coat.
- Few enzymes of own, none for metabolism.
- Viruses can not replicate, need a specific host cell.
- Viruses have no functional membranes or energy release mechanisms.
What are the steps in virus replication?
- 1. Attachment to the host cell
- 2. Entry and removal of capsid by host enzymes
- 3. Transcription of viral nucleic acid
- 4. Replication of viral nucleic acid (DNA or RNA), using host enzymes
- 5. Synthesis of capsid proteins
- 6. Assembly of new virus particles
- 7.Release of virions from host cell
What is a viroid?
- Smaller and simpler than a virus.
- Infectious pieces of RNA that cause some plant diseases.
What is a Prion?
Infectious proteins. Mis-folded proteins cause holes in brain tissue. Mad cow disease.
What is a retrovirus?
A virus that contains RNA which replicates by first transcribing RNA to DNA using reverse transcriptase. eg HIV
What are the most common Virus shapes?
- both can be enveloped - membrane-like layer.
- Complex eg bacteriophage
What environmental factors influence the growth of bacteria?
- Water and osmotic pressure
- Absence or presence of Oxygen
- Availability of nutrients
What is meant by optimal growth temperature?
The temperature at which bacteria grow best.
How do phychrophiles cause problems for humans?
Can grow in fridge, therefore spoil food.
What is the optimum temperature for bacteria involved in infectious diseases?
Mesophiles. 34-40 degrees C
Most bacteria are neutrophiles. So like a pH range of?
The internal pH of bacteria is?
What happens to bacteria in a hypotonic solution?
Higher water concentration outside the cell. Bacteria will swell. Cell wall prevent bacteria from bursting.
What happens to bacteria in a hypertonic solution?
Water in bacteria cell leaves via osmosis, cell contents shrink, cell wall stays ridged. cell will die.
What is an obligate aerobe?
What is an obligate anaerobe?
Bacteria that cannot survive in the presence of oxygen. eg, Clostridium, tetanus. can treat wound with hydrogen peroxide - decomposes to produce oxygen.
What is a facultative anaerobe?
Grows best with oxygen. can grow without it. eg E.coli
What are the oxygen requirements of a Microaerophilic organism?
Require small amounts of oxygen. 2-10% eg campylobacter
What is selective media?
Prevent growth of unwanted bacteria without inhibiting the growth of the desired bacteria.
What is differential media?
contains various nutrients that allow one bacterial species to be differentiated from another by how they change the media with a waste product.
Destruction of all microbes, including viruses and endospores.
Reducing the number of and eliminating certain disease causing microbes.
procedure to reduce numbers of microbes on skin or living tissue.
Reduce numbers to a safe level.
Provision of safe water supplies. eg sewage system
Inhibits growth, but does not kill.
use of sterile equipment and antiseptic to reduce contamination.
How does moist heat control microbial growth?
- kills them by denaturing the proteins.
100 degC for 10 min. some endospores survive 20 hours of boiling. Some viruses survive 30 min boiling.
121 degC 15 min. Steam under pressure. Kills everything
72 degC 15sec. Destroying pathogens and spoilage bacteria. Not sterilised.
How dies dry heat control microbial growth?
Kills microorganisms by oxidation.
Describe hot air sterilisation.
160-180 degC 1-2hours. used on things seam can't penetrate of will damage, eg oil
Used to destroy microorganisms in biological materials such as contaminated waste, soiled dressings and disposable equipment.
eg flaming of bacterial loop, materials non-recoverable.
How does low temperature affect microbial growth.
Refrigeration (0-7deg) bacteriostatic effect.
psychrophiles will still grow. eg listeria
Freezing renders bacteria dormant.
How does drying affect microbial growth?
With the absence of water microorganisms cannot grow, but may remain viable. bacteria, hours to months. endospores and viruses years.
How does UV radiation affect microbial grow?
Causes damage to the DNA of cells. Mostly used of surfaces or air.
Heat tolerant. can survive pasteurisation.
Heat loving, can't grow in low temp.
What is the time for LTLT?
63.5 degC 30 min
What is the temp and time for HTST?
72degC for 15 sec
What are the 6 important categories of chemical disinfectant?
- Quaternary ammonium compounds
Describe a use and limitation for chemical disinfectant phenolics
- Use - public toilets
- Limitation - irritating
Describe a use and limitation for chemical disinfectant Iodine/iodophores
- Use - wound disinfection
- Limitation - Stains
Describe a use and limitation for chemical disinfectant chlorine
- Use - pool treatment
- Limitation - inactivated by organic material
Describe a use and limitation for chemical disinfectant chlorhexidine
- Use - Handwashing
- Limitation - not active against virus or endospores
Describe a use and limitation for chemical disinfectant alcohol
- Use - Wipes for skin and equipment
- Limitation - endospores and some viruses not destroyed
Describe a use and limitation for chemical disinfectant quaternary ammonium compounds
- Use - Household disinfectants
- Limitation - inactivated by organic material.