Micro-organism, structure and function

Question 1

What is the definition of microbiology?

Answer 1

Biology of organisms which are too small to be seen by the naked eye

Question 2

What are transmissable Spongiform Encephalopathies?

Answer 2

They are infective proteins based on the prion protein.
They are expressed on the surface of neurons of all people.
When misfolded, they will come in contact with another protein and misfold that one. This transfers the disease along.

Question 3

Is a bacteria or virus smaller?

What size is a virus?

Answer 3

A virus is smaller.

A virus is in nanometre range. They are a collection of RNA and a protein.

Question 4

Give the characteristics for bacteria, eukaroytes and viruses

1. Visible under light microscope
2. Capable of free growth
3. Cell division
4. Genes separated from cytoplasm by membrane
5. Genome
6. Metabolically active

Answer 4

1. Virus isnt, others are
2. Virus isnt, others are
3. Viruses cant, others can
4. bacteria no, eukaryotes yes, n/a for virus
5. DNA for bacteria and eukaryotes, DNA/RNA for virus
6. Yes for bacteria and eukaryotes, no for viruses

Question 5

What can viruses infect?

Answer 5

Bacteria, plants and animals

Question 6

What is an oblique intracellular parasite?

Answer 6

A parasite that can only survive inside another host cell

Question 7

Explain the viral structure

Answer 7

• can form a icosohedral or helical shape
• is a nucleic acid packaged in a protein
• can be either DNA or RNA, double or single stranded
• can be a naked or enveloped virus (once packaged in a membrane)

Question 8

Give examples of naked and enveloped viruses

Answer 8

Naked ones = rhinovirus, cornovirus (caused polio)

Enveloped = HIV, influenza

Question 9

Give the steps for viral replication

Answer 9

1. Virus sits to the surface of the target cell
2. Gets into the cell by either fusion of cell membrane or endocytosis or simple translocation through membrane
3. Encoats itself within the host cell
4. Genome is formed before translation. More proteins are translated off the genome
5. More genome produced which then starts to form more virus particles.
6. So many of the virus inside the cell that it bursts open
7. They they go onto infect the next cell

Question 10

Give the bacterial structure

Answer 10

It is a lipid bilayer membrane with DNA as a single chromosome. This chromosome is associated with proteins for scaffolding but is free-floating.
Plasmids present with a few genes.
Can do protein synthesis.
Bacterial cell wall.
reproduction is binary fission

Question 11

How do we name them?

Answer 11

Genus, species, strain (in italics)

Question 12

Give a few things we can use to identify a type of bacteria

Answer 12

• shape and size
• arrangement of growing bacteria
• gram stain
• culture requirements
• biochemcial reactions
• antigenic structure
• nucleic acid technologies

Question 13

What is the main type of bacterial shape?

Answer 13

Bacilli (rod) and cocci (ball) stuctures

• strepto = chains
• staphyl = clumps

Question 14

Explain gram stain differncaition

Answer 14

• it stains for peptioglycan in the bacterial cell wall
• A gram negative organism also has a outer membrane. This membrane prevents the gram stain getting to the peptiogylcan so they will not stain.

Question 15

Give a few features of a bacterial cell wall

Answer 15

• capsule (carbohydrate surrounding)
• periplasmic space (space between plasma membrane and peptioglycan)
• LPS (lipopolysaccharide)
• lipoproteins anchor the outer membrane in place

Question 16

What can we identify in colony characterisics?

Answer 16

• surface texture
• colony morphology and size
• indicator dyes
• different nutrients

-haemolysis ( grow bacteria on a plate with red blood cells. This distinguishes between alpha, beta and gamma.
Alpha breaks down the cells but only locally, beta secretes toxins that break down RBC across the whole plate, gamma is far weaker and only targets cells which the bacteria can invade directly)

Question 17

How do we identify bacteria based on biochemical test?

Answer 17

• sugar fermentation profiles (see if the bacteria can produce certain sugars or biproducts)
• enzyme profiles (see what the bacteria can break down)

Question 18

How can we look an antigenic structures to classify bacteria?

Answer 18

• based on the specificity of antibody-protein interactions

- proteins on bacterial surface unique to that bacterium

Question 19

What are the 3 typing of a bacteria?

Answer 19

Serotyping = using antibodies to detect
Phagetyping = using bacterial viruses to bing to the bacteria
Genetic typing = typing based on the DNA sequence of the bacteria
- plasmid profile, chop up DNA and see what fragment size we get, probes (see if it reacts with a dye), PCR (sequence the DNA)

Question 20

Give the main differences between prokaryotes and eukaryotes

Answer 20

Prokaryotes

• no internal membrane
• rigid cell wall
• 70s ribosomes

Eukaryotes

• DNA encased in nucleus
• has mitochondria for metabolism
• no cell wall
• larger than bacteria
• 80s ribosomes

Question 21

Explain the main structure of a fungi

Answer 21

single or multi-cellular

digest food with extracellular enzymes

some can be dimorphic

Question 22

What are the two types of fungi?

Answer 22

• yeasts and moulds

Question 23

give details on the fungal cell wall

Answer 23

• made of 2 polymers
• lower layer of chitin which sits above cell membrane
• above this is a thicker layer of glucan (alpha 1,3 and alpha 1,6)
• manoproteins at top for the furry look

Question 24

What are Koch’s postulates?

Answer 24

1. The bacteria must be present in every case of the disease.
2. The bacteria must be isolated from the host with the disease and grown in pure culture.
3. The specific disease must be reproduced when a pure culture of the bacteria is inoculated into a healthy susceptible host.

Question 25

What are the 3 labels for bacteria for interaction with the host?

Answer 25

Symbiotic - provides a benefit to host Commensals - dont do anything Mutualistic - benefit to host and bacteria