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Microbiology > 2. Bacterial Anatomy > Flashcards

2. Bacterial Anatomy Flashcards

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Biology 101 flashcards
1
Q

What are the three basic shapes of bacteria?

A

Cocci (round), rods (long), and spirilla (spiral)

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2
Q

What are the characteristic arrangements of cocci?

A 
Chains 
Clusters 
Pairs (diplococci) 
Tetrads - groups of 4
Sarcinae - cubes of eight
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3
Q

What are the characteristic arrangements of rods?

A

Can have round ends, square ends, pointed ends.
Palisades - lie in sheets on top of each other
Acute angles - snap at point of division
Chaining

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4
Q

What are the characteristic shapes of spirilla?

A

Can vary from a slightly curved rod to a tight corkscrew.

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5
Q

What are involution forms?

A

Dead, degenerating, or dying bacteria.
Have weird bizarre forms.
Result of poor growth conditions, lack of nutrients, or antibiotic treatment.

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6
Q

Define cellular morphology. How are bacteria measured?

A

The size, shape, and arrangement.

Measured in micrometers.

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7
Q

What is a bacterial colony?

A

Group of bacteria that divide and grow together to form a visible round entity.

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8
Q

What is cellular morphology?

A

Microscopic appearance of bacteria on gram stained slides.

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9
Q

What is colonial morphology?

A

Macroscopic appearance of bacterial colonies after incubation.
Includes colour, consistency, hemolysis, size, edge appearance, etc.

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10
Q

What are flagella?

A

Long, thin, filamentous appendages that enable bacteria to move.
Is anchored to the call wall and cytoplasmic membrane.

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11
Q

What are the different arrangements of flagella on a bacterial cell?

A

Atrichous - none
Monotrichous - one, rapid darting directional movement
Lophotrichous - up to 6 on one end, rapid and more directional movement
Amphitrichous - both ends
Peritrichous - around, tumbling motion

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12
Q

Where are flagella found?

A

Some rods and spirals

Not cocci

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13
Q

What is motility?

A

The ability to move spontaneously and actively while consuming energy in the process.
Bacteria often rest between periods of motility.

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14
Q

Name and describe the two methods of determining motility.

A

Slide motility - look at a liquid culture microscopically

Motility media - inoculate a soft medium and observe for growth spreading in the medium

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15
Q

When is the best time to observe bacteria using slide motility?

A

During the log phase at room temperature.

Use 40x magnification

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16
Q

What are the tree types of movement that can be seen in a slide motility preparation?

A

Brownian movement - bacteria appear to vibrate or jiggle
Drifting or streaming - moves in flow with the liquid
Stages of slide motility - not all bacteria will be moving at the same time, reset period may occur, bacteria move against currents

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17
Q

What are some advantages and disadvantages of slide motility?

A

Advantages - rapid results, can tell the flagellar arrangements
Disadvantages - tedious and slow, may not show motility if bacteria have passed the log phase

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18
Q

What is motility media?

A

A semi solid nutrient medium that is clear enough to see the growth of bacteria

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19
Q

What are two methods of descending motility medium?

A

Plate method - single plate of medium used, incubated for 1-2 days
Tube method* - medium is inoculated with a straight wire about half way down a tube, incubated for 1-2 days, TTC may be added to give a red colour to better detect where growth has spread

20
Q

What are the advantages and disadvantages of using the media method?

A

Advantages - fast and easy, tube can give optimum conditions for motility
Disadvantages - some bacteria do not grow well below the surface of the medium

21
Q

What are bacterial capsules?

A

A viscous layer surrounding bacteria excreted from the cell (called glycocalyx). Must be organized and firmly attached to the cell wall to be called a capsule.

22
Q

What is the function(s) of bacterial capsules?

A

Interfere with phagocytosis
Increases virulence
May provide a protective layer

23
Q

What do colonies of capsulated bacteria look like in the lab?

A

Mucoid and slimy

Wet glistening appearance

24
Q

What are two problems that can occur in the lab when trying to detect capsules?

A

Shrinkage - caused by heat, drying and fixing to a slide. Can be prevented by using a wet preparation.

Development - most often present on the initial culture medium but may lack in subsequent cultures, good carbon and energy sources are needed, sucrose added to promote production

25
Q

What is negative staining?

A

The part of the cell you want to demonstrate remains unstained while all other material is stained.

26
Q

What substance is used in negative staining to view capsules?

A

India Ink (Negrosin)

Capsules appear as clear halos

27
Q

What is the composition of a bacterial cell?

A

Have a rigid layer outside the plasma membrane called the cell wall
The cell wall has a strengthening substance called Peptidoglycan
NAG and NAM are two sugars that make up the carbohydrate backbone

28
Q

What two groups are bacteria divided into when Gram staining?

A

Gram positive
Gram negative

This is based on their colour after Gram staining in the lab

29
Q

How can bacterial cell walls be damaged?

A

Antibiotics - able to break the Peptidoglycan of the cell wall
Enzymes - lysozyme can break bonds between sugars and Peptidoglycan
A Gram + cell wall is more susceptible than a Gram - cell wall as the Peptidoglycan is exposed on a Gram positive cell

30
Q

What is a Gram positive cell that has lost the cell wall called?

A

A protoplast

31
Q

What is it called when gram negative cell has its membrane broken down but some the outer layer remains attached?

A

A spheroplast

32
Q

What is a hypotonic solution vs. a hypertonic solution?

A

Hypotonic - water moves into the cell due to a lower concentration of water in the cell, causing rupture

Hypertonic - water leaves the cell due to a higher concentration of water within the cell, causes shrinkage and collapse

Both are lethal to bacterial cells

33
Q

What is an isotonic solution?

A

Has the same concentration of salt as inside the cell, no water moves in or out

34
Q

Describe step 1 of the Gram staining procedure.

A
    • Fix slide with crystal violet (C)
    • stain left on for 1 minute then washed with water
    • all cells are now stained deep purple
35
Q

Describe step 2 of the Gram staining procedure.

A

2.

  • flood the slide with Gram’s or Lugol’s Iodine solution for 1 minute and wash off with water
  • mordant: a substance that fixes dye to a cell
  • cells at this stage are stained purple to bluish-black
36
Q

Describe step 3 of Gram staining.

A
  1. Is the most important step
    - decolourize with acetone-alcohol (A) until no more blue colour can be seen coming off the slide
    - this is when differentiation takes place
    - Gram positive remain purple-blue
    - Gram negative decolourize and become colourless
37
Q

Describe step 4 of the Gram staining process.

A
    • counter stain with safranin (red) (S) for 1 minute
    • Gram positive cells appear purple to bluish-black
    • Gram negative cells appear pink to red
    • first examined under a microscope at 10x
    • once suitable areas are found, examine with oil immersion (100x)
38
Q

What is the KOH (potassium hydroxide) test?

A

A drop of KOH is placed on a slide and stirred with a straight wire. Gram negative organisms form a thread when the wire is pulled away because there is more lipid on the Gram neg cell wall.

39
Q

Explain the theory of the Gram stain reaction.

A

An intact cell wall is necessary to differentiate Gram positive and Gram negative bacteria.

40
Q

What are the differences between Gram negative bacteria and Gram positive bacteria?

A

Thickness of cell wall - Gram + thick, Gram - thin
Amount of Peptidoglycan - Gram + thick layer, Gram - thin layer
Amount of lipid - Gram + little, Gram - lots

41
Q

What nuclear material is included in a bacterial cell?

A

Chromosome - genetic material
Plasmids - aid in the survival of the cell, resistance to antibiotics, mate and exchange genetic info, produce toxins harmful to host cells

42
Q

What are Fimbriae and Pilli?

A

Fimbriae - non-flagellar hair-like structures usually found uniformly over the entire cell surface

Pili - longer structures than Fimbriae and only one or two per cell, often called sex pili as they form the connection between two cells when DNA is being exchanged

43
Q

What are the 4 processed used in bacterial cells to move materials a cross the cytoplasmic membrane?

A

Diffusion - passive movement from high to low concentration
Osmosis - passive movement of water
Facilitated Diffusion - passive movement from area of high to low concentration using carrier enzymes
Active Transport - requires energy, transport material from areas of low to high concentration

44
Q

What are bacterial spores?

A

One copy of the chromosome and a small amount of cytoplasm are isolated and when germination occurs the spore separates and becomes a cell

Gram positive rods are the only bacteria capable of producing spores (endospore)
Best time to see spores are during the death phase and are resistant to staining

45
Q

What are the functions of spores?

A

Enable bacteria to resist adverse conditions.

Heat, disinfectants, lack of nutrients, drying

46
Q

Do bacteria have ribosomes?

A

Yes!

Microbiology (7 decks)

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