Introduction

Question 1

Robert Hooke

Answer 1

• micrographia 1665
• first observations of microbial spores under a microscope
• 300x magnification

Question 2

Louis Pasteur

Answer 2

• germ theory of life, proved microbes were responsible for decomposition
• 1822-1895

Question 3

Robert Koch

Answer 3

• first linked cholera pandemic to cholera bacteria
• Koch’s postulus = steps needed to connect specific microbe to disease including infecting a healthy person with microbe
• 1843-1910

Question 4

how are prokaryotes different to eukaryotes

Answer 4

• no membrane bound organelles
• pili
• 70s ribosomes (eukaryotes have 80s)
• flagella (smaller)
• some have gas vesicles/ endospores
• nearly all have a cell wall, different from eukaryote cell walls
• no mitochondria or ER
• no cytoskeleton/microtubules

Question 5

Carl Woese

Answer 5

• used ribsosomal RNA to identify third domain of life, Archaea

Question 6

‘unseen majority’

Answer 6

<1% microbes can be grown on agar media

Question 7

phylogenomics

Answer 7

comparing whole genomes

Question 8

monophyletic groups

Answer 8

• natural grouping of organisms with one common ancestor
• usually categorised by synapomorphies

Question 9

archaea vs bacteria

Answer 9

• bacteria have peptidoglycan cell walls, archaea cells walls contain various polysaccharides, proteins, or glycoproteins
• the amino acid initiator for tRNA is formylmethionine in bacteria and methionine in archaea and eukarya
• RNA polymerase in archaea is more similar to eukaryotes
• bacteria have lipids in cell membrane

Question 10

why sequence rRNA?

Answer 10

• all organisms have ribosomes inherited from last universal common ancestor
• evolves slowly
• same role in all organisms

Question 11

properties of archaea

Answer 11

• none are pathogens
• usually extremophiles
• obligate anaerobes
• usually uncultured
• some methanogens or involved in nitrification

Question 12

origin of eukaryotes

Answer 12

• endosymbiosis of mitochondria from alphaproteobacteria
• most of bacterial DNA merged into main host nucleus
• host cell probably archaea

Question 13

metagenomics

Answer 13

analysis of genomes in a bulk sample e.g. sediment sample to analyse communities of microorganisms

Question 14

Lokiarchaeota

Answer 14

• archaea from Loki’s castle, deep ocean sediment in the Arctic ocean
• nearest eukaryotic relative
• had eukaryotic features related to cell function including a cytoskeleton with microtubules, genes relating to protein degradation and ER

Question 15

Asgard archaea

Answer 15

• relative of Lokiarchaea
• proposed common ancestor of eukaryotes
• Hiroyuki Imachi cultured it

Question 16

great oxygenation event

Answer 16

• 2.1bya evolution of photosynthesising cyanobacteria
• 1.6bya endosymbiosis of chloroplast in marine eukaryotes
• evolution of aerobic metabolism (mitochondria) and meiosis (probably linked) driven by a rise in O2
• colonisation of land

Question 17

HGT in bacteria

Answer 17

• transformation from lysis
• conjugation from pili
• transduction from virus

Question 18

inter-kingdom HGT

Answer 18

e.g. Agrobacterium tumefaciens
- interdomain HGT (prokaryote to eukaryote)
- transfers Ti plasmid into host nucleus
- triggers tumour growth in plant host, crown galls
- used to GM plants

Question 19

transposable genetic elements

Answer 19

‘junk’ DNA (40% of human genome) derived from retrotransposon DNA, stabilised into non-coding DNA

Question 20

retrotransposon DNA

Answer 20

• mobile genetic elements that can move about independent of meiosis/mitosis and can replicate after excision from genome
• encoding genes for transposition with long terminal repeats (LTRs) on either end
• closely related to retroviruses as it is copied from RNA to DNA using reverse transcriptase (unusual retroviral property)

Question 21

euryarchaea

Answer 21

closest archaea to eukarya