Bacteria

Question 1

Two cell shapes

Answer 1

Cocci - round

Bacilli - rod

Question 2

Features of Gram positive bacteria

Answer 2

• Bounded by single cytoplasmic lipid membrane.
• Thick peptidoglycan layer, multilayers
• Periplasmic space
• Low lipoprotein content
• Primarily exotoxins produced
• More susceptible to antibiotics

Question 3

Staining characteristics of Gram positive

Answer 3

• Thick peptidoglycan later retains the Gram stain
• Retains crystal violet dye
• Remains coloured blue or purple when washed with absolute alcohol and water

Question 4

Features of Gram negative bacteria

Answer 4

• Inner cell membrane is present
• Thin peptidoglycan layer
• Outer membrane with lipopolysacharides and phospholipids
• Primarily endotoxins produced
• More resistant to antibiotics

Question 5

Staining characteristics of Gram negative

Answer 5

• Due to thin peptidoglycan layer, can be decolourised and accept counterstain
• Doesn’t retain Gram stain when washed with absolute alcohol or water

Question 6

What culture to use for Gram negative and Gram positive

Answer 6

• MacConkey agar

Question 7

How to determine DNA species

Answer 7

PCR

Question 8

Capsule

Answer 8

• In Gram +ve and -ve bacteria
• Polysaccharide layer that lies outside the cell envelope bacteria
• Difficult to stain but can appear as a halo under a microscope
• Raise virulence factor as they prevent phagocytosis
• Not all bacteria have these

Question 9

Flagellum

Answer 9

• In Gram +ve and -ve
• Lash-like appendage
• Allow for different types of motility
• Not all bacteria have these

Question 10

Fimbriae

Answer 10

• In many Gram -ve and some Gram +ve
• Adherence main job
• Carry adhesins that attach to the substratum so bacteria can handle shear force and get nutrients
• Create virulence for E.coli, Bordetella pertussis, staphyloccus and streptococcus bacteria

Question 11

Cytoplasm

Answer 11

Material or protoplasm within a living cell, excluding nucleus

Question 12

Ribosomes

Answer 12

Minute particle consisting of RNA and associated proteins

Question 13

Cell wall

Answer 13

Rigid layer of polysaccharides lying outside the plasma membrane

Question 14

Peptidoglycan

Answer 14

• Polymer consisting of sugars and amino acids, forms a mesh-like layer outside the plasma membrane of most bacteria

Question 15

Chromosome

Answer 15

• Packaged and organised structure that contains most of the DNA of a living organism
• DNA organised in prokaryote into nucleoid

Question 16

Penicillin binding proteins

Answer 16

• Group of proteins characterised by their affinity for and binding of penicillin
• All β-lactam antibiotics bind to PBPs which are essential for bacterial cell wall synthesis

Question 17

Lipopolysaccharides

Answer 17

• Known as lipoglycans and endotoxins
• Found in the outer membrane of Gram negative bacteria
• Can be released during lysis of the cell
• They illicit a strong immune response in animals

Question 18

Exotoxins

Answer 18

• Toxin secreted by bacteria
• Can be secreted or released during lysis of the cell
• Can cause damage to the host by destroying cells or disrupting normal cellular metabolism

Question 19

Plasmid definition

Answer 19

• Small DNA molecule within a cell that is physically separated from a chromosomal DNA and can replicate independently

Question 20

How plasmid is transmitted from one bacterium to another

Answer 20

1. Transformation: direct uptake and incorporation of exogenous genetic material. Taking up DNA
2. Transduction: Foreign DNA from a phage introduced into a cell wall by a virus or viral vector.
3. Conjugation: Transfer of genetic material between bacterial cells by direct cell-to-cell contact by bridge-like connection between 2 cells

Question 21

Transduction mechanism in plasmids

Answer 21

Phage injects DNA
Phage enzyme breaks down host DNA
Cell creates new phages
Transducing phage inserts donor DNA
Donor DNA included in recipients chromosome due to recombination

Question 22

Bacteriophage

Answer 22

• Virus that infects and replicates within a bacterium
• Bacteriophages are composed of proteins that encapsulate a DNA or RNA genome
• Phages replicate within the bacterium following the injection of their genome into its cytoplasm

Question 23

Spore

Answer 23

• Small, round body inside bacterial cells
• When conditions become adverse, these are important for survival
• They are extremely resistant: can tolerate extreme dryness, some cannot die at subzero temps, some can spread poisonous chemicals

Question 24

Staphylococcus

Answer 24

Grapelike clusters

Question 25

Streptococcus

Answer 25

Chains of cocci

Question 26

Acinetobacter spp.

Answer 26

Non-motile