Microbes Flashcards
How long does microbes evolve? Position in ecosystem
Billion years
Fill in every available niche
Essential for global nutrient cycle
Great model for evolution
Louis Pasteur 1870s
2 bottles heated until no bacteria
Put in the air
Soon grow bacteria
Koch’ s postulates 1890
Extract bacteria from ill animal, culture, inject back to healthy animals, extract, compare and identify
Ratio of microbe and human
2% by mass
1:1 by cell
1:100 by gene
Why small cells?
Smaller cells are more efficient, can absorb more nutrients per unit volume
体积比表面积增加的快
whats the difference between life and rock
Self reproduction
Heritability
Evolvability
Individual
Population
Community
Metabolism and replication-continue input of energy and material
Variation and evolution-reproduction(competition)and replication(fitness)
Consumption and nutrient cycle-mass and energy balance
Plasma membrane
Structure and function
Hydrophobic tail and hydrophilic head
Signal, transport, adhesion
2 distinct biochemical systems in membrane
Metabolism: without membrane, the products of metabolism will quickly diffuse away, and membrane creates gradient which provide energy to synthesize atp
Information: without membrane, the cell cannot store information and make sure it permanently linked to the metabolic system
Why large cells inefficient?
Volume grow faster than surface area
Reproduction contain which 2 parts
Division in biomass
Replication of information
Definition of plasmid and its characteristics
Small DNA that not essential for normal function
Replicate at the same time with chromosomes, but daughter cells not always receive the same amount
Encode the conjugation, result in transfer through pilus
May encode function benefit or parasite host cell
What lead to evolution by natural selection?
Differential reproduction
DNA
mRNA
Protein
Info storage-base paire-nucleus or cytoplasm
Info retrieval-bases-cytoplasm
Product assembly-codons-ribosome
Product-amino acids-cytoplasm
2 theories about why genetic codes are redundant
- The frozen accident (Crick)
Accidentally happen and stuck
2.Optimal biochemistry in view of versatility, cost of synthesis
3 theories about the origin of life?
1.special creation
2.panspermia
Directed panspermia
Undirected panspermia
Misdirected panspermia
3.spontaneously generation
Based on the evolution speed of life
2 possibilities of spontaneous generation
1.arise spontaneously by natural process of self organization
2.continuous series of entities link chemical with life, evolve through natural selection at early point, taking over from self assembly
Experiment test spontaneous generation
1953 Stanley Miller and Harold C.Urey
2 possible routes of life
1.genetic first-RNA world
RNA can self replicate without cell
RNA can act as enzymes to catalyze reaction
Example:self splicing intron
2.metabolism first
Photosynthesis too complex
Hydrothermal is more possible
Ocean heat high pressure allow redox reaction occur
Respiration and fermentation
Fermentation: pyruvate is the electron acceptor
Respiration: glycolysis, oxidation of pyruvate, citric cycle, electron transport chain
Electron down hill, O2 is the final acceptor
NADH is electron carrier
metabolism-sequence in evolution
Fermentation
respiration
photosynthesis
oxygenic photosynthesis
aerobic respiration
The Winogradsky colume
Aerobic-oxygenic photosynthesis-autotroph
Anoxygenic photosynthesis-heterotroph
Anaerobic-respiration and fermentation-heterotroph(chemo)
Tree of life 2 ways to draw
Distance based
Parsimony
tree of life—3 types of relationship between species
Monophyly
Paraphyly
Polyphyly
Luca
Last universal common ancestor of all living organisms
2 daughter cells are bacteria and archaea
Characteristic of virus
1.DNA or RNA genome
2.not cell, need host cell to replicate
3.all forms of cells infected by bacteria
Virus—infection process
Bind with receptor
Enter
Release genome
Translation of viral polymerase
RNA replication and transcription
Translation
Combine and formation
Exocytosis
Adaptation tradeoff
Phage—1 type of HGT
transduction
lytic cycle（selective pressure）or lysogenic cycle（HGT）
Advantages of metabolism first
If have a source of energy, then it’s able to build a complex system, complex protein, gain the rna system
Genetic first advantages
The ability to reproduce
Have forms of inheritance, reproducing, increases the likelihood of that one of them developing and gain the ability to catalyze reactions and gain early forms of metabolism
