Systemic Bacteriology pt.1

Question 1

Give the main categories for the classifying microorganisms

Answer 1

• Appearance & Structural features
• Growth Requirements
• Enzyme/Metabolic tests
• Molecular test

Question 2

Which of a microorganism’s appearance and structural features are used to classify it

Answer 2

• Shape (coccus, bacilli, spirillum, etc.)
• Size
• Arrangement (chains, clumps, etc.)
• Cell wall (gram +ve/-ve)

Question 3

Give the common bacteria shapes

Answer 3

• Coccus (cocci)
• Bacillus (bacilli)
• Spirillum (spiral)
• Fusiform (*not really needed)

Question 4

Describe the shape of a coccus bacteria

Answer 4

Spherical

Question 5

Describe the types of division seen in cocci, and the cell arrangements this leads to

Answer 5

Division in 1 plane = Chains

Division in 3 planes = Clumping

Question 6

Describe the shape of bacilli

Answer 6

Rod-shaped

Question 7

Describe the cell arrangement most common is bacilli, and the division type that causes this

Answer 7

Bacilli are arranged in chains

This is causes by division on 1 plane

Question 8

Describe the arrangement of a diplococcus bacteria

Answer 8

Bacteria that exist as pairs of cocci

Have division on 1 plane

Question 9

Describe the shape, and gram of Vibrio bacteria

Answer 9

Vibrio are curved rods

They are gram -ve

Question 10

Name the 2 types of spiral shaped bacteria

Answer 10

• Spirillum (rigid)

- Spirochaete (flexible)

Question 11

Describe the differences and similarities between spirillum and spirochaete

Answer 11

Both are spiral shaped

Spirillum have rigid cell walls
Spirochaete have flexible cell walls

Question 12

Describe fusiform bacteria

Answer 12

• Anaerobic
• Gram -ve
• Tapered ends

Question 13

Are bacteria arranged in chains more common in gram -ve or gram +ve

Answer 13

The chain arrangement is more common in gram +ve bacteria

Question 14

Why are bacterial spores difficult to destroy?

Answer 14

They are inert (no protein synthesis, DNA replication, etc.)

So there are very few mechanisms for antibiotics to disrupt

Question 15

Describe the clinical significance of bacterial spores

Answer 15

After antibiotics have cleared an infection the spores (unharmed by the antibiotics) can re-inoculate the site

Question 16

Describe the colour difference between gram +ve and gram -ve bacteria after a gram stain

Answer 16

Gram +ve –> Purple

Gram -ve –> Pink

Question 17

Give a limitation of gram staining

Answer 17

Not all bacteria stain will

e.g.
Mycobacterium tuberculosis

Question 18

Give and define the classifications that indicate a bacteria’s tolerance of oxygen

Answer 18

Aerobic - Grows in oxygen

Obligate Aerobes - Require oxygen

Facultative Anaerobes - Tolerate oxygen

Obligate Anaerobes - Killed by oxygen

Question 19

Define a selective media

Answer 19

Media where the presence of a specific substance permits the growth of one organism over another

Question 20

Define differential media

Answer 20

Media incorporating chemicals that inhibit the growth of certain bacteria, allowing easy identification of a type of bacteria

Question 21

Define haemolysis

Answer 21

The destruction of red blood cells

Question 22

Describe the different types of haemolysis

Answer 22

α Haemolysis - Partial decomposition of the haemoglobin

β Haemolysis - Complete decomposition of the haemoglobin

γ Haemolysis - No decomposition of the haemoglobin

Question 23

Describe the visible characteristics of α, β,and γ haemolysis on a blood agar plate

Answer 23

α - Greening of the colonies

β - Clearing of the agar around the colony

γ - No effect on agar (but maybe slight browning of surrounding agar)

Question 24

Describe metabolic profiling of bacteria

Answer 24

The bacteria’s use of resources and its exoenzyme production

Question 25

Give 2 examples of exoenzymes produced by bacteria that are used in metabolic profiling

Answer 25

Catalase

Coagulase

Question 26

Give 2 examples of resources used by bacteria that are used in metabolic profiling

Answer 26

Carbon sources - e.g. sugars

Amino Acids

Question 27

Define serotype (serovar)

Answer 27

Microorganism classification based on the surface antigens

Question 28

Describe serological testing

Answer 28

Using specific antibodies to test for specific antigens

If there is a match, then agglutination occurs

Question 29

Describe the process of Polymerase Chain Reaction (PCR)

Answer 29

1) Heat denatures the DNA template (unzips)
2) Annealing of primers to template
3) Extension of primers via thermostable polymerase
4) 2 new copies of target sequence

Question 30

Describe how PCR is used to identify microorganisms

Answer 30

The successful amplification of the target DNA may indicate the presence of a specific organism

(Primers can only bind if the target DNA is present)

Question 31

Describe the role of the 16s rRNA sequence in microorganism identification

Answer 31

The 16s rRNA sequence can be sequenced to identify the microorganism

As different microorganisms have different 16s sequences

Question 32

Describe the role of MALDI-TOF in microorganism identification

Answer 32

Ionising radiation breaks up protein
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Mass spectroscopy used to analyse the protein fragments
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Fragments identify the microorganism