Reintro to Microbiology

Question 1

Name the major types of microorganisms

Answer 1

• Eukaryotic - protazoa and fungi
• Fungi
• Bacteria - prokaryotes
• Viruses
• Prions - infectious proteins

Question 2

Protozoa features?

Answer 2

Unicellular eukaryotes
2-100μm
Many are free living
e.g. Malaria
Often affect the immunocompromised
Mainly a threat in developing countries

Question 3

Fungi features?

Answer 3

Eukaryotic organisms with a variety of forms
Commercially important- baking, brewing
External, rigid cell wall- containing chitin
Filamentous or yeast forms
Many are dimorphic = ability to have 2 lifestyles
e.g. Candida

Question 4

Bacteria features?

Answer 4

Most numerous organisms
Adapted to inhabit almost all habitats
- Even those not based on sunlight- deep sea vents
Responsible for PLAGUE
Produce a range of toxins- virulence factors
Specialised cell walls
Prokaryotes - no internal membranous compartments

Question 5

How to classify bac?

Answer 5

1. Cellular form
   - Cocci (1)
   - Diplococci (2)
   - Tetrads (4)
   - Sarcina (4 behind 4)
   - Streptococci (wiggly)
   - Staphylococci (kite shape)
   Baclli:
   Branching
   Extended irregular rods
   Kidney bean
   Corkscrew
   Helical
2. Cell wall structure
   - Gram positive - 1 membrane = fuzzy part is peptidoglycan layer = retains stain = purple
   - Gram neg - 2 membranes and thin cell wall between the 2 = perioplasmic space = do not retain stain = pink/red stain

Question 6

What is a peptidoglycan?

Answer 6

A polymer of N-acetyl muramic acid and N-acetyl glucosamine (NAG)
Crosslinked via AA pentapeptides and anchored to cell wall

Question 7

What surface structures do bac have?

Answer 7

Flagellum = allows movement
Pili and fimbriae;
- Proteinaceous filamentous structures
- Used for attachment to host cells or surfaces
- Adhesins at the tip for host interaction
- Used for twitching motility
- Pseudomonas spp.

Question 8

What are pathogens? Example?

Answer 8

Disease causing bac e.g. Vibrio cholera - cholera

Question 9

What are opportunistic pathogens?

Answer 9

Commensals that sometimes cause disease e.g. MRSA, N.meningitis

Question 10

Where are commensals located? How much is there?

Answer 10

Main mass in digestive tract

1kg mass in bac

Question 11

What are commensals?

Answer 11

Unseen hordes - mainly harmless, colonise surfaces and mucosa

Question 12

What makes mycobacteria different?

Answer 12

Have a normal membrane, peptidoglycan and mycolic acids = more resistant = unusual cell well

Question 13

Features of mycobacterium spp? Example of a mycrobacterium?

Answer 13

Gram pos rods, unusual cell wall - mycolic acid
Impervious to gram staining
Zeen Ziehl-Neelson acid fast staining procedure; mycobacteria in red
E.g M. tuberculosis

Question 14

M.leprae significance? E.g of mycobacterium

Answer 14

First bac clinically associated with a disease - leprosy

Treated with antibiotics

Question 15

What causes chlamydia? Features? What does chlamydia cause?

Answer 15

Caused by C.trachomatis
Unusual gram neg cell wall
Unusual life cycle - elementary body facilitates spread, reticulate body (intracellular replication)
STI
Urethral and vaginal infec
Conjunctivitis
Infertility and ectopic pregnancies
Asymptomatic carriage important in spread - symptoms not obvious

Question 16

Examples of diseases as a carrier state?

Answer 16

Gonnorhoea, chlamydia

Question 17

What causes typhoid fever? Effects of this?

Answer 17

Salmonella typhi

Microorganisms remain in gall bladder and excreted in faeces when cured of typhoid fever = spread

Question 18

Virus features?

Answer 18

Obligate intracellular parasites
Causes HIV
Unable to reproduce without host factors
Viral genome uses host to encode viral proteins

Question 19

Outline the basic viral structure

Answer 19

Nucleic acid encapsulated by proteinaceous capsid
Varying shape and symmetry
Some further coated with lipid coat - enveloped e.g. HIV

Question 20

What is viral latency?

What is retroviral replication?

Answer 20

Infec does not result in lytic cycle

1. Incorporation into genome
2. Latent infec of host cell away from site of infec

Retroviral replication;
- mRNA does reverse transcription forming DNA - incorporates into genome of hose = replicates e.g. HIV

Question 21

Why is the lytic life style of viruses?

Answer 21

Virus internalised, host cell makes many copies of virus = released from cell

Question 22

What can latent infections do?

Answer 22

Can re-activate e.g. due to stress

Question 23

What do bacteriophages do? (is a virus)

Answer 23

Attack and kill bacteria - live in mouth

Question 24

Prion features?

Answer 24

Not truly a microorganism but is an infectious agent
Heat resistant, filterable, stick to instruments
Can be detected in tonsils but not outside lymphatics
e.g. CJD
Aggregate into long fibres and amyloid plaques
Likely transmission via brain tissue
E.g KURU

Question 25

What is Kuru? Symptoms and cause?

Answer 25

Fatal brain disorder
First symptoms = unsteady gut, tremors, slurred speech
Caused by cannibalism