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Cell Biology > Microbiology > Flashcards

Microbiology Flashcards

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1
Q

Why are microbes important?

A

Contribute to digestion, produce vitamin K, promote the development of the immune system, and detoxify harmful chemicals. And they are essential to making many foods such as bread, cheese, and wine.

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2
Q

Give some examples of microbes

A

Protozoa parasite

Toxic algae

Parasites

Fungi and their mycotoxins

Bacteria - E.coli, Listeria

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3
Q

Explain the structure of bacteria and naming

A

Prokaryotic cells

Mainly unicellular

Extremely diverse

Named using the binomial system

Example Bacillus subtilis

Bacillus - genus

subtilis - species

B. subtilis

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4
Q

Name and give the colour of the groups that bacteria are divided into on the basis reactions to the Gram stain

A

Gram-positive - purple (crystal violet)

Gram-negative - pink (safranin)

Gram indeterminate - variable or weak

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5
Q

Explain how bacteria are grouped based on cell wall structure

A

Bacteria that stain using Gram stain reagents:

Gram-positive e.g., in Staphylococcus aureus, a thick layer of PG retains crystal violet (purple) during destaining

Gram-negative e.g., Escherichia coli, crystal violet washed off, and safranin stains (pink) instead

Bacteria that do not stain with Gram stain reagents:

Bacteria with complex wall structures such as Mycobacterium tuberculosis (acid-fast bacteria) do not retain crystal violet well -> Ziehl Neelsen stain

Peptidoglycan-less bacteria e.g., Mycoplasma

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6
Q

What substance do bacterial cells contain in their cell walls?

A

Peptidoglycan

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7
Q

Name the components of gram positive cell envelope

A

Wall teichoic acid

Cell wall

Plasma membrane

Protein

Peptidoglycan

Lipoteichoic acid

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8
Q

Name the components of gram negative cell envelope

A

Porins

OMPs = outer membrane proteins

Inner/plasma membrane

Outer membrane

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9
Q

Explain what LPS endotoxin molecules are

A

Repeating sugar side chains (O antigens) attached to Lipid A in the outer leaflet of the membrane

LPS molecules
cause a net negative charge on the surface of the cell
may hinder access of molecules to the cell and, therefore, play a protective role

Endotoxins

  • are a component of the bacterial cell wall
  • induce septic shock when introduced into the bloodstream.
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10
Q

Name and explain bacterial surface structures

A

Flagella

Whip-like appendage

Motility, adherence, and virulence

Extend outwards from the plasma membrane and cell wall

Fimbriae/pilli

Hair-like, shorter, straighter, and thinner than flagella

Attachment and sex

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11
Q

Explain what Glycocalyx and S-layer in bacteria surface structures are

A

Glycocalyx

External to cell wall

Capsules and slime layers - polysaccharides or polypeptides

S-layers

Protein layers on the outside of the cell

Protection, attachment

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12
Q

Explain the 3 ways bacteria can be identified

A

Phenotype:

Morphology

Biochemical property

Cellular proteins:

MALDI-TOF mass spectrometry

Serotyping

Genotype:

16S rRNA

FISH whole genome sequencing

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13
Q

Explain the structure and function of fungi and what type of microorganism they are

A

Eukaryotic Microorganism

Can be single cell (yeast) or complex multicellular forms (molds)

Carbon sources from dead organism substrates or living organic material

Form Spores

The cell wall contains chitin, B-glucan, and mannans

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14
Q

Name the 3 things that the cell wall of fungi contains

A

Chitin

B-glucan

Mannans

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15
Q

What is the name given to bacteria that grow in liquid?

A

Planktonic

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16
Q

What is the name given to bacteria that grow on the surface?

A

Sessile

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17
Q

What is the name given to bacteria that grow on the surface as an organized community?

A

Biofilms

18
Q

Name the 4 stages in order of a bacterial growth curve in batch culture

A

Lag phase

Exponential growth phase (log)

Stationary phase

Death phase

19
Q

Explain what happens during the exponential growth phase and give the equation

A

Cells double at regular intervals

Each generation is a regular interval (doubling time)

Nt = N0 x 2n becomes Nt = N0 x 2 t/td

N0 = number of cells at time O

t = total growth time (4h)

Nt = number of cells after time (4h)

td = doubling time

20
Q

Explain the pH range for growth

A

5 to 9

21
Q

Explain what water availability is

A

Water availability is a measure of the amount of water available for hydration activities

22
Q

Explain ways to prevent bacterial growth

A

Control temperature

Remove water

Use extreme pH

Control oxygen availability

Add substances to prevent growth

Remove or reduce the number of microbes

23
Q

Name and explain the 3 levels of bacterial destruction

A

Sterilisation - destruction of all microbes

Disinfection - removal of microbes using physical or chemical means - does not necessarily involve removal of all microbes

Antiseptic - use of chemical agents on skin or living tissue

24
Q

Explain methods of sterilization and explain the temperature and how long each is carried out for

A

Autoclave (steam under pressure) - 121 degrees C for 15 to 20 minutes

Dry heat - 160 degrees C for 2 hours

Filtration - Depth filters, Membrane filters (0.22 um to 0.4t5 um pore size), HEPA filters - high-efficiency particulate air filters

Ultraviolet radiation (UV-C) - less than 16,000 uwaatt-sec/cm2

Ionizing radiation - X-rays, beta particles, and y- ryas

Gasses e.g. ethylene oxide - less than 3% EtO

25
Q

Explain the mechanism of action and germicidal range of alcohol (70%)

A

Mechanism of action:

Denaturation of proteins; bactericidal.

Germicide range :

Bacteria, mycobacteria, endospores, fungi

26
Q

Explain the mechanism of action of hydrogen peroxide (3 - 6%)

A

Mechanism of action:

Acts as a strong oxidative agent, DNA breaks

Germicide range:

Everything though some spores may survive

27
Q

Explain the mechanism and germicidal range of the following:

Formaldehyde

Chlorhexidine

Chlorine (bleach)

A

Formaldehyde

Mechanism of action:

Cross-linking of proteins, RNA, DNA

Germicidal range:

Everything

Chlorhexidine

Mechanism of action:

Cell wall disruption

Germicidal range:

Everything but endospores and some viruses

Chlorine (bleach)

Mechanism of action:

Combination of oxidation and chlorine of amino acids, lysis, and DNA breaks

Germicidal range:

Even though some spores may survive

28
Q

Give some factors that influence the effectiveness of disinfectants

A

Type of disinfectant

Number and location of microbes

Type of microbe (cell wall)

Amount of organic material present

Cocentration of disinfectant

Duration of exposure

Temperature of exposure

Biofilm

29
Q

Explain what a D-value is

A

Decimal reduction time is the time taken at a specific temperature and condition to reduce a microbial population by 90% or a factor of 10 i.e 1log10 reduction

30
Q

Explain the process of pasteurization, UHT, and Appertization

A

Pasteurization - Treatment of a food at a temperature and time designed to remove a specific pathogen associated with the food. E.g. milk 72 degrees C for 15s or 63 degrees C for 30 mins

UHT - ultra high temperature - 140 - 150 degrees C for 1 - 3s - Destroys mycobacteria and Brucella abortus

Appertization - sterilized by heating perishable goods in containers tightly closed (bottling, sealing, and heating)

31
Q

Explain the effectiveness of irradiation

A

Resistance to UV

Resistance to ionizing radiation

32
Q

When is irradiation treatment allowed?

A

To inhibit sprouting (potatoes, onions, etc)

Decontaminated dry food such as spices

Destrcution of parasites

Delay fruit maturation

33
Q

Name some of the chemicals used as food preservatives

A

Organic acid and esters

Parabens

Nitrite

Sulfur dioxide

Nisin

34
Q

Explain the 2 types of treatment for microbial disease

A

Antibiotics

Compounds that have antimicrobial activity originally isolated from natural sources e.g. penicillin G from Penicillium notatum

Non-antibiotic antibacterials (antimicrobials)

E.g. sulphonamides and trimethoprim

35
Q

Explain the Paul Ehrlich and the concept of the magic bullet

A

Founder of chemotherapy

Worked on selective staining of tissues (dyes)

Salvarsan (arsenical) - destroyed Treponema pallidum

Nobel Prize 1908

36
Q

Name 4 potential targets in bacteria

A

Translation

DNA Replication and Transcription

Cell wall synthesis

Folate Synthesis

37
Q

Name some of the foodborne disease caused by bacteria and which specific bacteria causes it

A

Chicken (Campylobacter jejuni)

Shellfish (Norovirus)

Meat ( Escherichia coli)

Eggs (Salmonella)

Fish (Ciguatera - marine algal poisoning)

Ready-to-eat meat (Listeria)

38
Q

Give the defense mechanism site and function of the defense mechanism on mucosal surface innate immunity

A

Mechanical Barriers - skin, mucosal membranes, mucin. Prevent microbial penetration

Flushing - Tears, urine, mucus, saliva, peristalsis, coughing, sneezing. Removal of microbes, prevention of attachment

pH - Fatty acids on skin, stomach acidity, vaginal acidity. Prevention of microbial growth

Lysozyme - Most sites and tissues. Break down peptidoglycan

Lacto-peroxidase - Mucosal membranes and lysosomes. kill bacteria by toxic superoxide radicals

Lactoerferin/Transferrin - Mucosal membranes, blood, and tissues. Chelates iron essential for microbial growth

Commensal microflora - Skina and most mucosal surfaces except the lungs. Compete for colonization sites, and nutrition and may produce antimicrobial compounds

39
Q

Explain what innate immunity cells are and explain the example of neutrophils and macrophages

A

Immune cells (eg macrophase and neutrophils) receptors recognize pathogen-associated molecular patterns

Recognize initiates phagocytosis and stimulates inflammation

40
Q

2 immune cells are macrophages and neutrophils. Explain both of their actions, and functions

A

Macrophages reside in tissues throughout the body. The function is phagocytosis (engulfing bacteria), activating bactericidal mechanisms, initiating inflammation, activating other immune cells (antigen presentation)

Neutrophils are present in the blood and are readily recruited to tissues. Function is phagocytosis and activation of bactericidal mechanism e.g. ROS, initiating inflammation

41
Q

Explain the role of commensal bacteria in the gut

A

Host metabolism and immunity

Regulate digestion

Regulate host metabolic homeostasis

Regulate immune system

Cell Biology (11 decks)

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