Microbial Diversity I

Question 1

On what basis are eukaryotes and prokaryotes classified?

Answer 1

Eukaryotes based on their 18S rRNA gene

Prokaryotes based on their 16S rRNA gene

Question 2

What is a type strain?

Answer 2

A well-characterised organism e.g. E.coli

Question 3

What is the area of using gene sequence to classify microbes known as?

Answer 3

Phylogenetics or systematics

Question 4

What are the three domains of life?

Answer 4

Archaea (“ancient things”
Eubacteria (“small staff”)
Eukaryota (“well, good” and “nut, kernel”)

Question 5

What are two phyla of Archaea that are abundant in the sea?

Answer 5

Chrenarchaeota: abundant in deep sea, oxidate NH3 thereby contributing to cycling of N2
Euryarchaeota: produce methane anaerobically as a final step in biodegradation of organic matter

Question 6

What are some examples of phyla of bacteria common in the sea?

Answer 6

OMG (oligotrophic marine gammaproteobacteria): abundant, not much is known about what they do
Chloroflexi: phenotypically diverse, include organisms that are aerobic thermophiles, anoxygenic phototrophs, and halorespirers that use halogenated organic compounds as energy sources
Marine Actinobacteria: include some important pathogenic strains of fish and marine mammals

Question 7

What significant genus is within the sub-phylum gammaproteobacter?

Answer 7

Vibrios: readily isolated from marine waters and sediments, often in association with eukaryotes
V. cholerae, V. fischeri (bioluminescence via quorum sensing)

Question 8

What are some examples of not yet cultured bacteria?

Answer 8

SAR86 cluster of Gammaproteobacteria
SAR116 cluster of Alphaproteobacteria
Alphaproteobacteria of SAR11 clade, constitutes up to half of microbial cells in oxygen-rich surface waters, role?
(SAR is a naming convention for uncultured bacteria, first found in Sargasso sea)