The microbial world and the tree of life Flashcards
What is a stromatolite
Layered sedimentary formations created mainly by photosynthetic microorganisms such as Cyanobacteria
What is the fossil evidence of early bacterial life?
Stromatolites in carbonate sediments (made of Cyanobacteria or blue green algae)
When is the oldest stromatolite from?
Archaean (2nd of 4 geologic Eons - Hadean, archean, Proterozoic, Phanerozoic)
4 impacts of microorganisms on human society
1) microbes and disease (improve understanding of disease, sanitation, public health)
2) microbes and agriculture (leguminous plants and nitrogen fixation, human intestinal tract, microbes inhabiting rumen of cattle and sheep)
3) microbes and food (spoilage and fermentation to make cheese, yoghurt, beer)
4) microbes and industry (microbes when growing as a biofilm can cause problems eg. Blockages or spoilage. But when brown in large quantities can also be beneficial in producing antibiotics, enzymes and chemicals.)
Classification of the five kingdom is still …
Ambiguous (for example are there five or six kingdoms? Is archaea a separate kingdom?)
What can happen between the five kingdoms ?
Can exchange genetic material
Timeline of seeing microorganisms (3 points)
XXX may need to fill in extra points later dk if it’s in prelims
700BCE: The Assyrians made a ‘Nimrud lens’ - rock crystal disk with convex shape
1660: Robert Hooke published Micrographia (descriptions of every he saw with his magnifying glass)
2009: ETEM (environmental transmission electron microscope)
Monera
Biological kingdom made up of prokaryotes (particularly bacteria)
Linnaeus
2 kingdoms plant and animal
1735
Haeckel
3 kingdoms Protista, plant and animal
1866
Chaton
2 empires
Prokaryote and eukaryote (coined these terms)
1937
Copeland 1956
4 kingdoms
Monera, protoctista, plant, animal
(He moves bacteria and blue green algae (prokaryotic groups) into separate MONERA group)
Whittaker 1969
5 kingdom
Animal, plant, fungi, protista, Monera
Woese et al 1977
6 kingdoms
Animal, plant, fungi, Protista, archaebacteria, eubacteria
Woese et al 1977
How did he propose this?
3 domains
Bacteria, archaea, eukaryota
Based on sequencing of 16S rRNA (highly conserved so present in all domains) used to created phylogenetic relationships rather than base it on morphological similarities
Main difference between archaebacteria and eubacteria
Archaebacteria usually found in extreme environmental conditions whereas eubacteria found everywhere on earth
What are archaea?
Similar to bacteria in size and simplicity of structure but different in molecular organisation.
Now believed to be an intermediate between bacteria and eukaryotes.
Wheat were archaea originally considered to be
Archaea appeared prokaryotic so we’re considered bacteria (they were thought to be ancient bacteria)
But then DNA sequence analysis revealed differences between archaebacteria and bacteria
Archaea four major phyla
- Phylum euryarchaeota
- Phylum crenarchaeota
- Phylum nanoarchaeota
- Phylum korarchaeota
Euryarchaeota
Most studied group, includes mostly methanogens (produce methane as metabolic byproduct in hypoxia conditions) and halophiles (grows in or can tolerate saline conditions)
Phylum crenarchaeota
Mostly found in marine environment
Phylum nanoarchaeota
Currently contains one species: Nanoarcheum equitable
Phylum korarchaeota
Consists of hyperthermothiles (organism can live at high temperatures)
What distinguishes archaea from eukaryotes and most bacteria ?
Presence of ether linkages in the lipids of their cytoplasmic membrane
Prokaryotes
Bacteria
Archaea
Eukaryotes
Plant
Animal
Fungi
Protoctista
How related are archaea to eukaryotes ?
Archaea (prokaryotes) are more closely related to eukaryotes than bacteria (prokaryotes) are
Characteristics that archaea and eukarya both have (suggests they are more closely related to eukarya than bacteria are to eukarya)
Methionine is initiator amino acid for protein synthesis
Lacks peptidoglycan in cell wall
Growth not inhibited by streptomycin and chloramphenicol
Histones associated with DNA
Contains several types of RNA polymerase
Origin of eukaryotic cells theory
Endosymbiosis theory - some of the organelles in eukaryote were once prokaryotes that were endocytosed. (
Eg. Mitochondria and chloroplasts are the same size as prokaryotic cells and divide by binary fission + have their own circular DNA
Gram stain results
Gram positive bacteria = purple = 90% cell wall made of peptidoglycan
Gram negative bacteria = pink = 10% cell wall made of peptidoglycan
Monotrichous bacteria
Single flagellum at one pole
Amphitrichous
Single flagella at each pole
Lophotrichous
Tuft of flagella at one pole
Peritrichous
Flagella all over surface
Atrocious
Non-motile bacteria that lack flagellum
How do bacteria and archaea differ
Bacteria cell wall has peptidoglycan, archaea cell wall does not
Bacteria cell membrane has lipid bilayer, archaea cell membrane has lipid bilayer or can have lipid monolayer
Bacteria plasma membrane lipids have fatty acids linking to glycerol, archaea plasma membrane lipids have phytanyl units linked to glycerol
Main summary of lecture
- microbes everywhere
- once tools we’re available we were able to classify them
- multiple classification schemes however not until molecular approaches that we could robustly define the classifications
- began to unravel differences and similarities between eukaryotes, bacteria and archaea.
