Applied Microbiology Flashcards
What are examples of edible fungi?
Mushrooms such as underground truffles, & Agaricus bisporus (button and portobellos)
What are mushrooms?
Fruiting bodies that are a source of proteins and minerals
What are examples of edible algae?
- Seaweed
- Red algae – Porphyra (nori)
- Brown algae – Macrocystis (alginate, a thickener)
Why are most bacteria unedible?
Nucleic acid too concentrated
What is the one bacteria that is edible?
The cyanobacterium Spirulina
What are ferment foods?
Food products modified biochemically by microbial growth
What are 3 reasons for fermenting food?
1) To preserve food by limiting growth of spoliage organisms & many pathogens
2) To improve digestibility (ex: breaking down lactose)
3) To add nutrients (ex: vitamins) and flavour molecules
What is usually needed for traditional fermented foods?
Indigenous flora (found naturally in food) or starter cultures (from a previous fermentation)
What are the 5 major classes of fermentation reactions and what is an example of each?
1) Homolactic acid (ex: yogurt)
2) Propionic acid (ex: swiss cheese)
3) Heterolactic acid (ex: kefir)
4) Ethanolic (ex: wine)
5) Alkaline (ex: Brie cheese)
What happens in milk fermentation?
- Lactic acid fermentation with Lactobacillus & Streptococcus
- Followed by rennet proteolysis, rendering casein insoluble
- Cleaved peptides coagulate to form a semisolid curd
What are the steps of cheese production?
- Milk is filtered and subjected to pasteurization
- Fermenting microbes are added to a starter culture
- Drop in pH and/or added rennet help denature the milk protein casein, which coagulates and precipitates out of solution (curds)
- Solid curd is cut
- Curd is lightly heat-treated
- Pressed curd is shaped into a mold
- Cheese is ripened or aged
What is pickling?
Fermentation in brine (high salt)
How does pickling work?
High salt selects for specific bacteria (Gram positive), sometimes starter cultures are used
Which microorganisms are used for pickling?
Pediococcus, Streptococcus, Lactobacillus, or Leuconostoc depending on the food and process
What are 2 examples of fermented cabbage?
Sauerkraut & kimchi
What are 2 examples of fermented meats?
Montreal smoked meat & genoa salami
For what food is ethanolic fermentation used?
Bread
What microorganism is used in Baker’s yeast and Brewer’s yeast?
Saccharomyces cerevisiae
What is the reaction that takes place in ethanolic fermentation?
Pyruvate –> ethanol + CO2
What molecule causes bread to rise?
CO2
What does beer arise from?
Alcoholic fermentation of grain
What is the process of making beer?
Barley grains are germinated, allowing enzymes to break down starch to maltose for yeast fermentation
What is the primary sugar that is fermented in the making of beer?
Maltose
What produces some of the special flavours in beer?
Secondary products, such as long-chain alcohols and esters
What does wine derive from?
Alcoholic fermentation of fruit, usually grapes
What is the process of making wine?
- Grapes are crushed to release juices
- For white wine, the skin is removed
- Yeast ferments sucrose, fructose, and glucose to ethanol
- Red wine & some whites undergo malolactic fermentation by bacteria which converts malate to lactate plus CO2 reducing acidity
Which microorganism is involved in malolactic fermentation?
Oenococcus oeni
What can’t a starter culture be developed for the making of chocolate?
The fermentation involves a succession of populations
What is food spoilage?
Microbial changes that render a product obviously unfit or unpalatable for consumption
What is food contamination/poisoning?
Presence of pathogens in food
What causes dairy products to be soured?
Excessive fermentation
What causes dairy products to be bittered?
Bacterial proteolysis
How are meat and poultry products putrefied?
Decarboxylating bacteria which produce amines with noxious odors
Why do seafoods spoil rapidly?
Because their unsaturated fatty acids rapidly oxidize
How do plant foods spoil?
Excess growth of bacteria and molds, which can cause them to wilt, brown, and lose texture
What are characteristics of Listeria monocytogenes
- Psychrotolerant bacterium
- Invades cells of intestinal epithelium
- Causes listeriosis
What are 6 physical means of preservation?
- Dehydration & lyophilization
- Controlled or modified atmosphere
- Pasteurization
- Canning
- Ionizing radiation
- Refrigeration & freezing
What are 3 chemical means of preservation?
- Organic acids
- Esters
- Other organic compounds
What is industrial microbiology?
The commercial exploitation of microbes, includes food production & preservation
Industrial microbiology includes the production of…
- Vaccines, pharmaceuticals, & therapeutics
- Industrial solvents & biodegradable plastics
- Genetically modified plant & animal cells
What is type 1 diabetes?
Beta-islet cells are destroyed by immune system
What is type 2 diabetes?
Insulin receptors on cells are desensitized to insulin
Who discovered the mechanism for diabetes?
Frederick Banting
When was insulin first produced and by whom?
In 1921 by Frederick Banting & Charles Best
Why can’t animal insulin be used in humans?
Many patients form antibodies against the foreign proteins, which causes inflammation & allergic responses
What is the structure of insulin?
- 51 amino acids
- Two chains – A & B held together by disulfide bridges
How can human insulin be manufactured?
- Extract and purify A & B chains
- A & B chains connected via disulfide bridges
- Results in pure synthetic human insulin
What kind of bacteria reduces the spread of pancreatic cancer?
Radioactive
Why is pancreatic cancer considered the “silent killer”?
Cancer spreads before primary tumor detected
What does lysteria monocytogenes have to do with pancreatic cancer?
When injected into tumor-bearing mice, bacteria selectively delivered to metastases where it spread cell-to-cell without being eliminated by the immune system
What does turbidimetric measures of bacterial growth assume?
That cells remain evenly distributed in their liquid growth medium
When cells remain evenly distributed in their growth medium, what is optical density proportional to?
The log of the number of cells in suspension
What does sessile mean?
Microorganisms grow attached to a surface
What does planktonic mean?
Microorganisms live in a liquid medium and float around
What can sessile cells grow into?
Biofilms
What is an example of a biofilm in a human?
The “film” that develops on unbrushed teeth
What is a biofilm?
An attached polysaccharide matrix containing embedded bacterial cells
What are the 4 stages of biofilm formation?
- Reversible attachment of planktonic cells
- Irreversible attachment of the same cells
- Cell growth & production of polysaccharide
- Further development to form a tenacious and nearly impenetrable mature biofilm
What is necessary for initially forming a biofilm?
Flagella
What are crucial to biofilm maturation?
Thin hairlike structures called type IV pili
What causes cystic fibrosis?
Development of a biofilm containing Pseudomonas aeruginosa
What are benefits of biofilms to bacterial growth in nature?
- Protection from harmful chemicals
- Barrier to grazing by protists
- Prevents bacterial cells from being washed away into a less-favourable environment
Why might humans want to manipulate their commensal bacteria?
To enhance the positive benefits of certain selected bacteria
What are probiotics?
Intentionally ingested live microorganisms used to change or reestablish GI microflora
