2. Bacterial Anatomy

Question 1

What are the three basic shapes of bacteria?

Answer 1

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

Question 2

What are the characteristic arrangements of cocci?

Answer 2

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

Question 3

What are the characteristic arrangements of rods?

Answer 3

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

Question 4

What are the characteristic shapes of spirilla?

Answer 4

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

Question 5

What are involution forms?

Answer 5

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

Question 6

Define cellular morphology. How are bacteria measured?

Answer 6

The size, shape, and arrangement.

Measured in micrometers.

Question 7

What is a bacterial colony?

Answer 7

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

Question 8

What is cellular morphology?

Answer 8

Microscopic appearance of bacteria on gram stained slides.

Question 9

What is colonial morphology?

Answer 9

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

Question 10

What are flagella?

Answer 10

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

Question 11

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

Answer 11

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

Question 12

Where are flagella found?

Answer 12

Some rods and spirals

Not cocci

Question 13

What is motility?

Answer 13

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

Question 14

Name and describe the two methods of determining motility.

Answer 14

Slide motility - look at a liquid culture microscopically

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

Question 15

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

Answer 15

During the log phase at room temperature.

Use 40x magnification

Question 16

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

Answer 16

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

Question 17

What are some advantages and disadvantages of slide motility?

Answer 17

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

Question 18

What is motility media?

Answer 18

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

Question 19

What are two methods of descending motility medium?

Answer 19

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

Question 20

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

Answer 20

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

Question 21

What are bacterial capsules?

Answer 21

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.

Question 22

What is the function(s) of bacterial capsules?

Answer 22

Interfere with phagocytosis
Increases virulence
May provide a protective layer

Question 23

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

Answer 23

Mucoid and slimy

Wet glistening appearance

Question 24

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

Answer 24

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

Question 25

What is negative staining?

Answer 25

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

Question 26

What substance is used in negative staining to view capsules?

Answer 26

India Ink (Negrosin) Capsules appear as clear halos

Question 27

What is the composition of a bacterial cell?

Answer 27

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

Question 28

What two groups are bacteria divided into when Gram staining?

Answer 28

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

Question 29

How can bacterial cell walls be damaged?

Answer 29

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

Question 30

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

Answer 30

A protoplast

Question 31

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

Answer 31

A spheroplast

Question 32

What is a hypotonic solution vs. a hypertonic solution?

Answer 32

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

Question 33

What is an isotonic solution?

Answer 33

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

Question 34

Describe step 1 of the Gram staining procedure.

Answer 34

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

Question 35

Describe step 2 of the Gram staining procedure.

Answer 35

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

Question 36

Describe step 3 of Gram staining.

Answer 36

3. 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

Question 37

Describe step 4 of the Gram staining process.

Answer 37

4. - 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)

Question 38

What is the KOH (potassium hydroxide) test?

Answer 38

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.

Question 39

Explain the theory of the Gram stain reaction.

Answer 39

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

Question 40

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

Answer 40

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

Question 41

What nuclear material is included in a bacterial cell?

Answer 41

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

Question 42

What are Fimbriae and Pilli?

Answer 42

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

Question 43

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

Answer 43

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

Question 44

What are bacterial spores?

Answer 44

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

Question 45

What are the functions of spores?

Answer 45

Enable bacteria to resist adverse conditions. Heat, disinfectants, lack of nutrients, drying

Question 46

Do bacteria have ribosomes?

Answer 46

Yes!