Bacterial cell morphology and structure

Question 1

Bacterial cell shapes

Answer 1

Rod = bacilli
Corkskrew = spirochaetes
Comma = vibrios
Spherical = cocci 
Spiral = Spirilla

Question 2

Bacterial arrangements

Answer 2

Chain, cluster, pair

Question 3

Nucleoid

Answer 3

Localisation of genetic material DNA

• Location of chromosomes and associated proteins,
• Usually not membrane bound
• Usually one closed, circular, double-stranded DNA molecule
• Super coiling and nucleoid proteins (not histones) aid folding

Question 4

Plasmids

Answer 4

• Extrachromasomal DNA found in bacteria, archaea and some fungi
• It is small, closed circular DNA and it exists and replicates independently of chromosome

Question 5

Define episome

Answer 5

independent extrachromosomal DNA that may integrate into chromosome and be inherited during cell division

Question 6

How are plasmids classified?

Answer 6

By mode of existence, spread and function.

Question 7

Bacterial cell wall characteristics

Answer 7

Almost all bacteria have a cell wall
Contains peptidoglycan (murein),
Maintains shape of bacterium and helps protect cell from osmotic lysis and toxic material (may contribute to pathogenicity)

Question 8

What/ where is peptidoglycan?

Answer 8

Peptidoglycan is a mesh-like polymer of identical subunits forming long strands

is a rigid structure that lies just outside the cell plasma membrane

And has two alternating sugars:
N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)

There are two types (based on gram stain)

Question 9

What are the two types of bacteria?

Answer 9

Gram negative - stain pink/red and have a thin peptidoglycan layer and outer membrane

Gram positive - stain purple and have a thick peptidoglycan layer

Question 10

What shape is peptidoglycan and how are they linked?

Answer 10

Peptidoglycan strands have a helical shape and chains are cross-linked via peptides for strength.