SW - Bacteriology III

Question 1

What are the challenges of studying microbes?

Answer 1

Recognition of microbial diversity depends heavily on analysis methods

• especially given that 99% are not culturable!

Question 2

What has a lack of agreement over what constitutes a species led to? (3)

Answer 2

• Miscalculations of diversity.
• Misunderstanding of environmental systems.
• Inability to compare between studies

Question 3

What were the traditional species concepts?

Answer 3

‘species’ – fundamental unit in Linneus’ classification (pre-Darwin) i.e. breeding populations.

Mayr (1963) Biological species concept:

• A fundamental ecological and genetic unit.
• Groups of interbreeding natural populations that are reproductively isolated

Question 4

Name 3 factors that affect speciation in bacteria?

Answer 4

• Relatively fast generation times
• Adaptive mutations
• Horizontal gene transfer and the ‘core genome’

Question 5

What 3 mechanisms are involved in Horizontal gene transfer?

Answer 5

Bacterial transformation

• Release of DNA

Bacterial transduction

• Release of phage

Bacterial conjugation

• Fusion of cells

Question 6

Core genome vs Pan-genome

Answer 6

Core genome -
Found all the time

Pan-genome -
All extra genomes added

Question 7

What are the 2 agents of horizontal gene transfer?

Answer 7

Prophage:

• Phage genome inserted into the linear structure of bacterial chromosome

Plasmid:

• Extra-chromosomal DNA molecule

Question 8

What can gene transfer alter?

Answer 8

Extra genes are incorporated into the cell without disrupting it

• Can alter phenotypic expression

Question 9

What is Diversity measured as?

Answer 9

Diversity can be measured in terms of the species richness and/or abundance and/or genetic variability of organisms

Question 10

How was microbial diversity recognised over the years?

Answer 10

Early – gross morphology, cell shapes and colonies.

Then - biochemical attributes.

Now – differences at molecular level.

Question 11

Polyphasic taxonomy

Answer 11

Consensus classification – that different information into a classification containing minimum contradictions

Information includes:

• Phenotypic data (e.g. biochemical tests, fatty acid composition).
• Genotypic data (e.g. DNA fingerprints).
• Phylogenetic data (e.g. rDNA sequences).