Bacterial Structure And Classification

Question 1

What are the characteristics of coccus bacteria?

Answer 1

They are spherical, ovoid or round in shape

Question 2

What are the characteristics of bacillus bacteria?

Answer 2

They are rod shaped bacteria

Question 3

What are the characteristics of spherilli bacteria?

Answer 3

They are spiral shaped bacteria

Question 4

What are the characteristics of gram positive bacteria and what colour do they stain?

Answer 4

Stains blue and purple
Have a thick peptidoglycan layer which have teichoic acid molecules present
Only have a cytoplasmic membrane

*spores are exclusive to Gm+ bacteria eg Clostridum difficile and botulinum

Question 5

What are the characteristics of gram negative bacteria and what colour do they stain?

Answer 5

They have an outer membrane and a cytoplasmic membrane and in between these two layers is the periplasm which contain the single layer of peptidoglycan.
* also has LPS which is highly toxic

Stains pink/red

Question 6

What is serotyping?

Answer 6

Use of antibodies for specific parts of bacterium that are different for each strain
Eg capsule, O- antigen and flagellum are immunogenic

Question 7

Which species of bacteria is resistant to acid fast stain ?

Answer 7

Myobacterium as they have lots of mycolic acid (lipid) in cell walls

Question 8

How can bacteria be classified?

Answer 8

• gram+ or - (cell wall property)
• morphology
• nutritional and enzymatic properties
• protein profiling
• genome sequencing

Question 9

What is significant about the 16S rRNA sequence?

Answer 9

RNA component of the ribosome that is unique for each bacterial species

Question 10

List the 4 ways bacteria can exchange genetic material:

Answer 10

• transformation = uptake of short fragments of DNA
• Transduction = transfer of DNA via a bacteriophage that then infects another bacterium
• Conjugation = transfer of DNA via sexual pilus (requires cell-cell contact)
• Transposons = jumping genes/mobile genetic units that integrate into genome