SW - Bacteriology II

Question 1

Taxonomy vs phylogeny

Answer 1

Taxonomy: Science of biological classification. Includes classification, nomenclature and identification

Phylogeny: Comparative analysis of an organism based on evolutionary relationships

Question 2

How does the 16S rRNA sequence help produce a phylogenic tree?

Answer 2

Variable and conserved regions

• Compared conserved regions to produce a phylogenic tree

Question 3

What are 18S rRNA sequences used for?

Answer 3

18S rRNA used for eukaryotes

Question 4

Why do gram-positive and gram-negative bacteria stain differently in Gram stain?

Answer 4

Gram-positive bacteria stain purple with Gram stain

• This is because they have a thick cell wall without an outer membrane

Cyanobacteria

Gram-negative bacteria stain red with Gram stain

• This is because they have a thin cell wall with an outer membrane

Salmonella

Question 5

What are 3 features of Archaea?

Answer 5

• Lack of peptidoglycan in the cell wall
• Have different types of lipids in the membrane (ether linkage)
• Mostly studied for life in extreme environments e.g. deep-sea vents

Question 6

What are 4 features of Protista (eukaryotes)?

Answer 6

• Unicellular eukaryotes that inhabit water and soil and feed on bacteria and small particles
• Reproduce sexually and asexually.
• They absorb nutrients through their outer membranes or ‘wrap themselves around’ their prey to ingest.
• Classification system is based primarily on motility and morphology

Question 7

What are 5 features of Viruses?

Answer 7

• Obligate intracellular parasites – cannot replicate by themselves.
• Have no machinery for making proteins, etc.
• Have limited host range determined by a viruses requirement for attachment to host cells (receptors).
• Belong to no kingdom.
• ds DNA, ss DNA, ds RNA, ss RNA – usually organised as single linear or circular molecule of nucleic acid.

Question 8

What is composed in the viral structure?

Answer 8

• Nucleic acid (DNA or RNA)
• Capsid – protein subunits – protect nucleic acids
• Receptors – host specificity

Question 9

What occurs during the Lytic cycle of a virus? (5)

Answer 9

1. Attachment
2. Penetration
3. Biosynthesis
4. Maturation
5. Release

Question 10

What occurs during the Lysogenic cycle of a virus? (3)

Answer 10

1. Virus attaches and injects DNA – incorporation into host = PROPHAGE
2. Prophage DNA passed on to daughter cells
3. DNA can excise and enter lytic cycle

Question 11

What are mutations caused by? (3)

Answer 11

1) Errors occurring during replication.

2) Errors occurring during DNA repair – damage cause by:

• UV
• Chemicals (e.g. H2O2)
• Other stresses (e.g. heat)

3) DNA recombining after gene transfer from an external source

Question 12

Crenarchaetoa (2) and Eurarchaeota (3)

Answer 12

Crenarchaetoa

–Thermophilic & hyperthermophilic.
–Cool marine planktonic waters.

Euryarchaeota

–Methanogens – use H2 to reduce CO2 to CH4
–Halophiles – live in very high salt environments
–Thermoacidophiles – have an optimum growth temperature between 60 – 80C; live at low pH.