Microbes

Question 1

What are the categories of microbes in size order (small - large)?

Answer 1

"Prions" (10-8)
Viruses (10-7)
Mycoplasma/chlamydiae/rickettsia  - intracellular obligates (10-6)
Bacteria (10-5)
Single cell fungi - yeasts (10-4)
Protozoa (10-4)
Multicellular fungi -aspergillus (10-3+)
Helminths (10-3+)

Question 2

Describe the Baltimore classification of viruses

Answer 2

I - dsDNA -> mRNA
II - ssDNA -> dsDNA -> mRNA
III - dsRNA -> mRNA
IV - (+)ssRNA -> (-)ssRNA -> mRNA
V - (-)ssRNA -> mRNA
VI - (-)ssRNA-RT -> DNA/RNA -> dsDNA -> mRNA
VII - dsDNA-RT -> mRNA

Question 3

Name the 3 categories of DNA viruses and a popular example for each

Answer 3

ssDNA non-enveloped:
Parvovirus 19 (common mild childhood infection - foetal abnormalities in pregnant women)

dsDNA non-enveloped:
Adenovirus, HPV

dsDNA enveloped:
Herpes, hepatitis B, molluscum contagiosum (warty growths with a spot)

Question 4

Name the 4 categories of RNA viruses and a popular example for each

Answer 4

ssRNA (+) icosahedral non-enveloped:
Coxsackievirus (aseptic meningitis), echovirus, enterovirus, hepatitis A & E, norovirus - mostly faeco-oral transmitted

ssRNA (+) icosahedral/helical enveloped:
HIV, hepatitis C, rubella, encephalitis viruses, yellow fever virus

ssRNA (-) helical enveloped:
Ebola, measles, mumps, influenza, respiratory syncytial virus

dsDNA icosahedral non-enveloped:
Rotavirus

Question 5

Some viruses are oncogenic, name one and the cancers it is commonly attributable to

Answer 5

Human Papilloma Virus (HPV) - cervical, penile and anorectal cancers

Question 6

What are bacteriophages and why are they important?

Answer 6

Viruses that affect bacteria

Involved in the horizontal transmission of bacterial genes including antibiotic resistance

Question 7

Name and describe the 3 main bacterial shapes

Answer 7

Coccus - spherical
Spirillus - spiral
Bacillus - rod-like

Question 8

Name the 3 main morphologies of bacterial colonies and the prefix used for each

Answer 8

Clusters - Staphy
Chains - Strep
Pairs - Diplo

Question 9

Describe the difference between gram positive and negative bacteria

Answer 9

Gram Positive:
All Ps - purple, positive, thick peptidoglycan cell wall

Gram Negative:
Red/pink, negative, two cell membranes (outer lipopolysacchride) with no thick peptidoglycan