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BI302 > R.O Lecture 1 & 2 > Flashcards

R.O Lecture 1 & 2 Flashcards

1
Q

What are microbes?

A

Bacteria, fungi and viruses

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2
Q

Taxonomy

A

A method of grouping bacteria. The science of classification

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3
Q

Binomial Nomenclature

A

“two-name”

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4
Q

True or False the Three-domain classification system supersedes kingdom classification

A

True

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5
Q

Approaches to identifying bacteria

A

-Microscopy: Light v Electron

-Morphology-Staining: Gram/Spore etc.

-Biochemical Tests

-Growth conditions: Molecular Biology Techniques

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6
Q

Dichotomous Key

A

A tool used to identify bacteria.

-Uses Paired Statements “either-or” choice

-Can be useful for practical reasons but have limitations

-Molecular methods are most accurate for classification

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7
Q

Light Microscopy

A

Note Limit of resolution for bacterial cells using light microscopy.

-Bright-field
- Dark-field
- Confocal
- Phase-contrast
- Normarsky
- Fluorescence

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8
Q

Electron Microscopy

A

TEM: Transmission electron micrograph
Resolution to 1nm
Magnification up to 500,000 X Cross-sections, usually 1D

SEM: Scanning electron micrograph
Resolution to 20 nm
Magnification up to 50,000 X Surface/Exterior 3D views

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9
Q

Describe Specimen Preparation for Light Microscopy

A
  1. Wet Mount: Allows visualisation of microbial motility
  2. Smear: Loopful of media containing microbe of interest
  3. Air dry
  4. Heat fixation:
    -Kills organism
    -Adheres to slide
    -Take up dyes more effectively
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10
Q

Name the Dyes used for staining techniques

A

-Cationic/basic (Methylene Blue, Crystal Violet, Safranin, Malachite Green)
-Anionic/acidic (Eosin, Picric Acid)

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11
Q

Name the types of stain used for staining techniques

A
  • Simple (1 dye, basic cell shapes/ arrangements)
  • Differential (2+ dyes, distinguishes between cell types/ parts of an organism)
  • Special Stain
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12
Q

Explain Simple Stain

A
  • Uses a single dye, do not distinguish organisms or structures by different staining reactions.
  • Example - Methylene Blue, Safranin (red) and Crystal Violet (purple)
  • Shows sizes, shapes and arrangements of cells.
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13
Q

Differential Stains

A
  • Use two or more dyes that react differently with various kinds or parts of bacteria, allowing them to be distinguished.
  • Example Gram Stain
  • Distinguishes Gram negative and gram positive bacteria
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14
Q

Special Stains

A
  • Identify various specialized structures
  • Example Schaeffer Fulton Spore Stain
  • Endospores retain malachite green stain, vegetative cells accept safranin counterstain and appear red.
  • Allows visualisation of hard to stain bacterial endospores such as members of genera Cloistridium and Bacillus
  • Spore stain is slightly modified as spores do not stain easily due to their resistant structures.
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15
Q

Describe the nature of the Catalase Biochemical Test

A

Hydrogen peroxide (H2O2) is poured over heavy growth of an organism on an agar slant; release of o2 bubbles indicates the presence of catalase, which oxidises H202 to H20 and O2

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16
Q

Name the methods of obtaining pure cultures.

A

Physical techniques: Streak Plate Method and Spread Plate Method

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17
Q

Explain the Spread Plate method

A

Isolating different bacterial species.
Can be used in combination with the streak plate method to isolate pure colonies from a mixed culture.

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18
Q

Name the types of growth media used in clinical setting.

A

Selective Media : Encourages growth of some microbes while surppressing growth of others. (may contain antibiotics ect.)

Diffferential Media: Includes a component that causes an observable change in the media in response to a particular biochemical reaction ( e.g. pH/colour change)

Enrichment Media: Contains ingredients that enhance the growth of particular microbes that may be present in relatively low numbers; doesn’t suppress others.

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19
Q

Name the molecular methods for bacterial identification/classification.

A

▪Genetic Homology:
-Base Composition
-DNA/RNA sequencing
-DNA Hybridisation
-Protein Profiles/Amino Acid Sequencing
-Ribosomal Properties (rRNA)
▪MALDI-ToF mass spectrometry
▪Immunological Reactions
▪Phage Typing

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20
Q

What does the Three-domain classification system consist of?

A

Bacteria, Archaea, Eukarya

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21
Q

Describe Prokaryotes

A

*Genetic Material is not membrane enclosed; circular chromosome

*Lack other membrane-enclosed organelles

*DNA is not associated with histone proteins

*Most cell walls contain the complex polysaccharide peptidoglycan

*Divide by binary fission; Asexual reproduction only

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22
Q

Describe Eukaryotes

A

*Membrane-enclosed nucleus; typically paired chromosomes

*Endoplasmic reticulum, Glogi apparatus, Lysomsomes ect.

*DNA packaged, tightly folded around histone proteins

*Cellulose/chitin found in plant/fungal cell walls

*Mitosis and/or meiosis; Sexual/Asexual reproduction

23
Q

What is the diameter and length of bacteria

A

Diameter: 0.2 –2 µm; Length: 2 –8 µm

24
Q

What are the 3 basic shapes of bacteria.

A

-Spherical (Coccus)
-Rod-like (Bacillus)
-Spiral

Other Shapes: Star, Spindle, Square, Triangular, Irregular

25
Q

What way do bacteria divide/reproduce?

A

Bacilli divide only along their short axis.
Asexual reproduction only

26
Q

What are the functions of the cell wall?

A

Functions:
- Maintains shape
- Prevents rupturing due to osmosis
- Anchorage for flagella

Often Porous

Can contribute to virulence (ability to cause damage to host)

Site of action for some antibiotics

Composition varies

27
Q

Peptidoglycan

A

Most important cell wall component. Consists of a carbohydrate backbone which is made up of repeating units.

28
Q

Describe the outer membrane

A

-Primarily Gram negatives (Gram-positive bacteria lack an outer membrane)
-Phospholipid bilayer external to cell wall
-Some protective qualities (e.g. Penicillin)
-Contains Lipopolysaccharide (LPS)

29
Q

Descirbe the Periplasmic Space

A

-Primarily Gram negatives

-Between Cell Membrane and Cell Wall

  • Metabolism Site
30
Q

Periplasm

A
  • Is part of cell wall in Gram Positives
  • Consits of peptidoglycan, proteins and metabolites
31
Q

Teichoic Acid

A

Another component of cell wall.

-Gram positive only
-Glycerol, phosphates, ribitol
-Polymer, 30 units long, extends through cell wall
-Attachment sites for phages/Ion movement

32
Q

What are the steps to Gram Stain

A
  1. Crystal Violet (1 minute) Drain, rinse. All purple
  2. Iodine is added. Iodine acts as mordant to set stain.
  3. Decolorise with alcohol and rinse with water.
  4. Safranin - Drain rinse and blot.
    Gram + = purple
    Gram - = red (pink)
33
Q

Gram Positive Bacteria (reaction to stain)

A

Thick peptidoglycan layer: Retain crystal violet dye following alcohol destain.

  • purple
34
Q

Gram Negative Bacteria (reaction to stain)

A

Relatively thin peptidoglycan layer:
Lose Crystal violet dye following alcohol destain
(pink)

35
Q

Acid-fast Bacteria
(Reaction to carbon fushsin stain)

A

Thick cell wall, 60% lipid: Retain carbon fushsin stain following acid-alohol destain

Examples include Mycobacterium species

Carbol fuchsin is used as the primary stain dye to detect acid-fast bacteria because it is more soluble in the cells’ wall lipids than in the acid alcohol.

36
Q

Cell Membrane

A

*Fluid-mosaic model: Phospholipid bilayer and proteins
*Regulates entry/exit of materials
*Synthesizes cell wall components, assists with DNA replication
*Protein secretion, respiration, captures ATP

37
Q

Name the internal bacterial structures

A

(Cell wall and membrane) Nucleoid and Plasmids Ribosomes
Inclusion Bodies
Spores

38
Q

Nuclear Region (Nucleoid)

A

Nucleoid: Usually single large circular chromosome. Circuluar shape for protection

No nuclear envelope/histones(DNA-associated proteins)

39
Q

Plasmids

A

Are seperate to the chromosome.

*Usually circular, dsDNA, extrachromosomal
*Replicate independently
*Can be gained/lost/transferred
*Additional genes

40
Q

Ribosomes

A
  • Involved in protein translation

-Consist of protein and rRNA (ribosomal RNA) components

-Sites of Protein Synthesis

-Cytoplasm

-Eukaryotic ribosomes(80S) v Prokaryotic ribosomes(70S)

-Antibiotic target (e.g. Streptomycin, erythromycin) Prokaryote specificity

41
Q

Inclusion Bodies (reserve deposits/storehouses)

A

Granules and Vesicles/vacuoles

42
Q

Granules

A

Tightly packed single substance that does not dissolve readily in the cytoplasm; not membrane enclosed; contents can be metabolised to produce energy/supply other metabolic processes E.g. Glycogen granules, polyphosphate granules

43
Q

Vesicles/vacuoles

A

Membrane enclosed structures found in certain bacteria. May contain lipids orgas or iron etc.

44
Q

What leads to the development of highly resistant endospores?

A

*Nutrient depletion can lead to the development of highly resistant endospores

45
Q

Describe endospores

A

*Dehydrated cells with thick walls and additional layers
*Unique to Bacteria: Occurs in Bacillus, Clostridiumand some other Gram-positives (Not the same as fungal spores)
*Not a reproductive mechanism; survival
*Endospores are not metabolically active
*Resistant to heat, drought, many chemicals, radiation

46
Q

What are the 3 stages of germination?

A

1) Activation:Damage to Spore Coat

2) Germination Proper: Spore’s enzymes break down peptidoglycan, Water enters

3) Outgrowth: Metabolism resumes if adequate nutrients are available

47
Q

Name the pathogenic spore formers

A

Bacillus anthracis, Clostridium botulinum, Clostridium tetani, Clostridium difficile

Can be resistant to usual methods of sterilisation/food preservation: heating, freezing, chemicals, desiccation, radiation etc.

48
Q

Autoclaving

A

Moist heat sterilisation (121*C, 15mins)

49
Q

Name the external Bacterial structures

A

Flagella, Pili, Glycocalyx

50
Q

What are the possible arrangements of the flagella?

A

Arrangements:

  • Monotrichous: single, polar
  • Lophotrichous: >2 flagella at one/both poles
  • Amphitrichous: One at each pole
  • Peritrichous: Distributed all over.

Note differences between gram-negative and gram-positive flagella

51
Q

How do flagella motility

A

Rotation of flagella
Run: Anti-clockwise, then Tumble: Clockwise

52
Q

What are the types of pili ?

A

Pili (fimbrae) and specialised pili.
* These are shorter structures than the flagella
* Conjugation Pili: Transfer of Genetic Material
* Attachment Pili

53
Q

Glycocalyx

A

All polysaccharide containing substances external to cell wall

Capsule :
Protective Structure, can contribute to virulence Complex polysaccharides arranged in a loose gel

Slime Layer: Thinner than Capsule Less tightly bound to cell wall Protects against drying, traps nutrients, adherence, protection

BI302 (11 decks)

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