Week 5 Review

Question 1

What are the different ways of preventing food spoilage? Explain each method.

Answer 1

Use osmotic pressure by curing
- Microbes can’t survive in high salinity so foods are preserved with salt, nitrates, nitrites, or sugar

Canning
- The food is blanched or steamed to fill a can easily. This process also lowers the microbial population and destroys enzymes that alter the food. The cans are then filled to the brim, leaving as little space as possible, and then the can is steamed once again to drive out any air spaces. The cans are immediately sealed and sterilized with pressurized steam. The can is cooled and is ready to be packaged.

Aseptic packaging
- Pre-sterilized products are put into packages using an aseptic technique

Irradiation
- Gamma, x-ray, or electron beams are used, to prevent foodborne illnesses, preserve food, control insects, and delay sprouting

Pressure
- Fresh foods and liquid foods are put under very high pressure to prevent spoilage, while also preserving the color and flavor of the food

Fermentation
- Addition of yeast to ferment sugars and produce CO2 and ethanol

Question 2

What organisms are involved in making each type of cheese?

Answer 2

Hard cheeses = produced by lactic acid bacteria
Semisoft cheeses = ripened by penicillium on the surface of the cheese
Blue and Roquefort = produced by penicillium inside the cheese

Question 3

What organism is used to make alcoholic beverages? What are the fermentation products?

Answer 3

Yeast is used to make alcoholic beverages. Yeast ferments sugars and produces CO2

Question 4

What are the steps in making beer and wine? How are they different (example: substrate)?

Answer 4

Beer:
Brewing: malt and hops boiled together for sterilization

Cooling and fermenting: wort (hot mixture) is cooled to 25C, then yeast is added and the mixture is transferred to the fermentation chamber

Priming and bottling: sugars are added before bottling

Aging: yeast will ferment sugars and produce CO2

Wine:
- Grapes are picked and tested, and then crushed and destemmed
- Sulfite is added to kill undesired yeasts and bacteria
- Yeast inoculum is added and fermentation occurs
- The result is pressed to separate solids from wine and the wine is clarified in settling vats, and then filtered
- Wine is aged and then bottled

Differences:
- In beer, you start with hops barley
- Fermenting sugar

• In wine, you start with grapes
• Fermenting plant sugar
• Undergo malolactic fermentation

Question 5

Why does grape wine-making require malolactic fermentation?

Answer 5

• When the sugars in grapes are used to make products, malic acid is produced which makes the wine taste strongly bitter
• In malolactic fermentation, lactic acid bacteria is used to convert malic acid into lactic acid (weaker)

Question 6

Name industrial fermentation products.

Answer 6

Vitamins
Amino acids
Steroids
Xanthan
enzymes

Question 7

How are biomass and bioconversion used for alternative energy sources and for single-cell protein products (SCP)?

Answer 7

Biomass, under bioconversion, produces biofuels like methane, ethanol, and hydrogen
- Biofuels are renewable replacement fuels
- Ethanol is in gas (90% gas, 10% ethanol)

Single Cell Protein (SCP) are proteins that are produced by microbes that ferment biomass
- SCP products are used as a substitute for protein-rich food (human food and animal feed)

Question 8

What are some advantages and disadvantages of SCP?

Answer 8

Advantage:
- Rapid growth rates
- Variety of substrates
- Easy manipulation of genetic material
- High protein content
- Low overhead (less land)

Disadvantage:
- High nucleic acid which increases uric acid
- Cell wall indigestible
- Gastrointestinal reactions

Question 9

What are the steps in the nitrogen cycle?

Answer 9

Ammonification
- Bacteria and fungi convert nitrogenous waste into ammonia (NH3)

Nitrification
- Nitrifying soil bacteria converts ammonia (NH3) to nitrites (NO-2) and then to nitrate (NO3-)

Denitrification
- Soil bacteria use nitrate as a terminal electron acceptor in anaerobic respiration and convert it to nitrogen gas (N2), returning to the atmosphere

Nitrogen Fixation
- Take N2 gas from the atmosphere into ammonia NH3 (easily made into macromolecules)

Question 10

Give examples of bacteria in the nitrogen cycle.

Answer 10

Ammonification = many
Nitrification = nitrosomonas, nitrobacter
Denitrification = bacillus, pseudomonas
N2 Fixation = axobacter, cyanobacteria, purple and green bacteria

Question 11

What are the steps involved in typical wastewater treatment?

Answer 11

Flushed toilet water goes into waste water tanks, and go through a filter called a bar screen that removes large debris from the water

Then at the sedimentation tank, solids settle to the bottom as sludge

The sludge goes to a sludge digester that gets rid of odors and harmful organisms, and then transported to solid disposal where solids are sent to a landfill or used as fertilizer

At the sedimentation tank, water goes to secondary aeration that provides oxygen for microorganisms, then goes to secondary clarifier where microorganisms decompose organic material and absorb nutrients

The liquid goes to a disinfection tank, killing remaining harmful bacteria, and then is discharged into waterways

Question 12

What is the difference between etiology and pathogenesis?

Answer 12

Etiology = the cause of disease
Pathogenesis= the “course” of the disease

Question 13

How are infection and disease-related?

Answer 13

Infection= the invasion and growth of pathogens in the body
Disease= the actual damage or improper functioning of tissues

Question 14

Name locations in the host where abundant microflora can be found.

Answer 14

Upper respiratory tract (nose, throat)
Eyes
Mouth
Skin
Gastrointestinal tract
Outer genitourinary (lower urethra in both sexes)

Question 15

Which locations have no normal microbiota?

Answer 15

Lower respiratory tract
Peritoneal cavity
Muscles
Circulatory system
Central nervous system

Question 16

How does competitive exclusion/ microbial metabolism affect the growth of pathogens? How does it protect against infection?

Answer 16

Competitive exclusion/microbial antagonism: normal microbiota compete with pathogenic microorganisms, so slows/prevent pathogenic growth

Protect by:
- Competing for nutrients
- Producing harmful substances
- pH and available oxygen

Question 17

What are the different types of symbiosis? Give examples of each type.

Answer 17

Commensalism: one organism benefits, the other is unaffected
- Corynebacteria surface of the eye

Mutualism: both organisms benefit
- E. coli produces vitamin K; large intestines provide nutrients for E. coli

Parasitism: one organism benefits at the expense of another
- Salmonella typhi causes typhoid fever

Question 18

Under what conditions do normal microbiota cause disease?

Answer 18

Organisms can obtain access through broken skin or mucous membranes

The host is weakened (therapy for cancer, transplants)

Damage to normal microbiota by antimicrobial drugs may lead to secondary infections

Question 19

What do Koch’s Postulates establish? What are the steps in Koch’s Postulates? What are some exceptions to Koch’s Postulates?

Answer 19

Koch’s Postulates establish microorganisms cause specific diseases.

Steps:
- The same microorganism is present in every case
- Microorganisms isolated from the host and grown in pure culture
- Microorganism from pure culture causes disease in “healthy” animals
- Pathogen isolated from “healthy” animal = original microorganism

Exceptions:
- The disease may be caused by a number of different microbes
- Some pathogens cause several disease conditions
- Some pathogens only cause disease in certain organisms

Question 20

How is a disease diagnosed?

Answer 20

Look at:
Signs and symptoms the patient is showing
Communicability of microorganism
Host’s conditions
Pattern of disease
Frequency disease
severity/duration of disease

Question 21

What is the difference between signs and symptoms?

Answer 21

Signs = objective changes that can be observed or measured
Symptoms = subjective changes noticed only by the host

Question 22

What is the difference between communicable and noncommunicable diseases?

Answer 22

Communicable = transmitted from infected to susceptible host
- Contagious disease: easily spread

Non-communicable = not usually transmitted
- Some microorganisms that grow outside the body
- Weakened host

Question 23

What is the difference between incidence and prevalence?

Answer 23

Incidence = number of new cases (risk)
Prevalence = total number affected in a population (how widespread)

Question 24

What are the different types of infection? Give examples.

Answer 24

Severity of duration:
Acute infection: develops rapidly but lasts only a short time
- Common cold

Chronic infections: slower but continue to reoccur over extended periods
- tuberculosis

Latent infections: the causative agent may remain inactive for some time but becomes active
- Shingles by varicella virus

Host environment:
Localized infection: microorganism confined to a particular tissue
- abscesses

Systemic (generalized) infection: microorganism carried by the circulatory system to different tissues
- measles

Question 25

What is sepsis and what are the types of sepsis?

Answer 25

Sepsis: a toxic inflammatory condition caused by microbes (mainly bacteria and toxins) spreading from a certain tissue

Bacteremia: the presence of bacteria in the blood

Fungemia: the presence of fungi in the blood

Viremia: the presence of a virus in the blood

Toxemia: the presence of toxins made by microorganisms in the blood

Question 26

What is the difference between pathogenicity and virulence?

Answer 26

Pathogenicity = ability to cause a disease by overcoming host defense
Virulence = degree of pathogenicity

Question 27

How is virulence measured?

Answer 27

Estimated through experimental studies of the lethal dose
- LD50: least lethal dose that kills 50% of the animals in the test group

Question 28

What are the portals of entry?

Answer 28

Mucous membranes:
- Gastrointestinal tract
- Respiratory tract
- Genitourinary tract
- Conjunctiva

Skin: parenteral access when mucous membrane or skin are penetrated or injured

Question 29

In what ways do pathogens damage the host? Give examples.

Answer 29

COVID-19 upregulates cytokines (cell messengers that activate/suppress certain cells)
- IL-1B induces other cells to make cytokines that attract other immune cells
- Some patients have cytokine storm (inflammatory response)

Siderophores: take iron from the host’s iron-transporting proteins, forming a siderophore-iron complex
- Iron is needed for bacterial growth but low free iron concentration
- Bacterial receptors bind to the siderophore-iron complex and uptake iron

Toxins: poisonous substances produced by microorganisms that can inhibit host cell function or kill the host

Question 30

What are the two main types of toxins? Be able to compare and contrast each.

Answer 30

Exotoxins (Gram +)
- Immediately released into the surrounding environment
- Proteins made by pathogenic bacteria and secreted during the log phase
- A-B toxins, membrane-disruptive toxins, and superantigens

Endotoxins (Gram -)
- It is not released until the bacteria is killed by the immune system.
- lipopolysaccharide (LPS) found on the outer membrane of gram negatives released when bacteria die
- Cause pyrogenic response (fever)
- Release TNF (tumor necrosis factor)
- Binds to cells and alters metabolism
- damages blood capillaries, leads to loss of fluids, and decreases blood pressure

Question 31

Describe the groups of exotoxins

Answer 31

Grouped by action:
A-B Toxins: A does the damage, B is recognition to enter the cell
Bacteria release toxin
- Toxin enters the cell by endocytosis
- A subunit dissociates from B
- A subunit moved to the cytoplasm
- Toxic action of A initiates cellular changes

Membrane-disruptive toxins: lyse host cells by disrupting plasma membrane
Include:
Leukocidins: kill leukocytes by forming protein channels and preventing phagocytosis by macrophages
Hemolysins: kill erythrocytes
Ex: staphylococcus and streptococci

Superantigens
- Antigens (bacterial proteins) that provoke a very intense immune response
- Non-specifically cause proliferation of T cells
- T cells stimulate the release of excess cytokines (regulate an immune response)
- Cytokines enter the bloodstream and cause a massive inflammatory response, sepsis shock, death
Ex: toxic shock syndrome, food poisoning

Question 32

Give examples of exotoxins

Answer 32

Diphtheria toxin (Corynebacterium diphtheria): A-B toxin that interferes with protein synthesis

Cholera toxin (Vibrio cholerae): A-B toxin causes cells to secrete fluids and electrolytes (ions that maintain osmotic balance)

Botulinum toxin and tetanospasmin (clostridium): A-B neurotoxins