Need to know Flashcards
What are Kochs Postulates?
1) The micro-organism must be found in abundance is all organisms suffering from the disease but should not be found in healthy organisms.
2) The microorganism must be isolated from a diseased organism and grown in pure culture.
3) The cultured microorganism should cause disease when introduced into a healthy organism.
4) The microorganism must be re-isolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent.
-In modern times however, it has been shown that many micro-organisms that cause certain diseases do not follow some/most of these rules.
What is HIV?
- A retrovirus that causes an infectious disease, it leads onto AIDS in many cases
- It targets the bodies immune system
How is HIV spread?
- Sexual intercourse
- Needle sharing
- Breast feeding
- Exchange of bodily fluids
How does HIV cause the infection?
- Attacks wbc - CD4+
- Inserts its genes into cell’s DNA using this to manufacture more virulent particles
- CD4+ cell count decreases progressively until it reaches a threshold that means the person develops AIDS
- HIV can ‘hide’ from the body’s immune system and is only detected when virulence is too high to fight
Koch postulates and HIV cures?
- There is yet no cure for HIV/AIDS but it can be controlled with anti-retroviral drugs
- One case of ‘cure’ has been seen in a patient with leukemia who had a full bone marrow transplant, the donor had a rare genetic mutation that was resistant to the virus
- Koch’s postulates: Viruses are difficult to grow in vitro in pure cultures
What is HPV?
- A virus proven to cause cervical cancer
Does HPV fulfil Koch’s postulates?
- No as many people have one of the HPV strains without getting cervical cancer, commonly transmitted through intercourse
- Yes - known as the primary cause, experiment investigated the prevalence of HPV in cervical cancer tumours, found in 93% of them. Modern techniques found that it was prevalent in 100% of tumours
What is Vibro cholera?
- Gram -ve bacterium
- Some strains cause the disease cholera
What are the symptoms of cholera?
- Diarrhea
- Vomiting
- Severity can lead to very fast dehydration and loss of electrolytes
How does cholera cause disease?
- Usually taken into the body via infected food or water
- Enters small intestine via endocytosis
- Produces cholera toxin
- Toxin causes chloride ion protein channels in plasma membrane of small intestine epithelial cells to open up
- Chloride ions move into small intestine lumen
- Build up of ions lower water potential of lumen therefore water moves out from blood across epithelial cells into the small intestine lumen via osmosis
- Mix of water with feces to cause diarrhoea
Cholera treatment?
- Oral rehydration solution, water alone not good enough, need to replace electrolytes
- ORS is drink that contains salts like sodium and sugars like glucose
What are lactic acid bacteria?
- Gram +ve bacteria
- Low GC
- Acid tolerant
- Can be rod or cocci
- Usually found in decomposing plants and milk products
- Produce lactic acid as major metabolic product of carbohydrate fermentation
What positive effect do they have on certain foods?
- Prevent food spoilage
- Production of acid - acidification - inhibits MO growth
- Som LAB produce proteinaceous bacteriocins which also prevent MO growth
- Some studies show they produce antifungal peptides
Describe LAB metabolism
- Aerotolerant anaerobes
- Homolactic fermentors: Only produce lactic acid
- 1 molecule of glucose to 2 molecules lactic
- Unable to make and use haem & cannot make cytochromes that are key ETC components
- They produce hydrogen peroxide and need to export this into external environment therefore die in virto
What industrial uses are there for LAB?
- Food production
- Sauerkraut - Lactobacillus which produced lactic acid as well as alcohols and hydrocarbons which combine to form esters to contribute to sauerkraut’s unique taste
- Yoghurt - LAB ferment the milk to produce it. Lactobacillus bulgaricus and Streptococcus thermophilus (some laws require all yoghurts to produce these two cultures)
Why is fermentation of food used in the food industry?
- Preserve food
- Improve flavour and smell
What is the general idea of fermentation?
- Process of converting sugar to acids, gases and/or alcohol
- Common in yeast and bacteria
- Can happen in oxygen starved human muscle cells
- Glucose —> ethanol + CO2
Give 4 examples of food produced using MO
- Cheese
- Beer
- Bread
- Vineagar
Describe how MO are used in cheese production
- Milk is primary ingredient
- Milk heated to kill off unwanted harmful bacteria
- Starter culture of LAB added
- Ferments lactose, produces lactic acid
- Curd formed as milk coagulates
- Typical LAB for cheese - Lactococcus lactis & Streptococcus salvarius
- After acidification - rennet is added to further encourage milk to solidify
- Curds cut then salt may be added, acting as preservative & adding flavour
How are MO used in beer production?
- Malted barley and malted wheat
- Brewing
- Starch broken down into sugary liquid called wort
- Sugars fermented by yeast into alcohol & CO2
- 2 main species - Saccharomyces cerevisiae & Saccharomyces
- Top fermenting yeasts produced ale, bottom produce lager
- Temp ussed for top to add esters and flavours of beer to give fruity tast
- Hops preserve and add bitter bitter taste
Mo in bread?
- CO2 produced causes dough to rise
- Yeast used usually Sacchromyces cervisae species
- Biological leavening agent bacteria contributes to bread making
- Sourdough gets taste by LAB lactobacillus sanfanciscenis as it produces lactic acid
Rickettsia
Clamydia
Obligate intracellular organism
- cant produce atp as missing stuff for respiration therefore need cells for energy
- rick - arthropod vector, fliesm ticks lice
- causes typhus - organ failure
- clamydia - couple of types
- pneumonia
- trachomatis - tracoma, eyelid rolls back, eyes dry and go blind
- clamydia most common sti - pelvic inflamatory disease - infertile
MO & Vinegar
- Acetobacter: gram -ve aerobic rods
- Ferments alcohol - apple cider, wine, potatoes
- Form film on top, mother on vinegar - starter cultivator of acetic fermentation
- Clostridium converts sugar to acetic acid in anaerobic fermentation cannot tolerant too acidic so must be concentrated
- Antibacterial properties strong useful for cleaning
which are imflammatory
clostridium - (c difficile- diarrhea)
-canned food and under cooking resistant endospores, botulinum which cause botulism which is dont even have to eat, just have to eat endospores which create neurotoxin which messes with heart beat and respiration. Fatal (more common in infants) soil and water - inflammatr
Helobacter - ulsers - diarrhoea
