Origin and evolution Flashcards
What is the origin of all living things?
LUCA
What did the LUCA form?
Bacteria
Archae
Eukaryotes
What are the two types of evidence for evolution?
Fossils
DNA and protein sequences
Since when have biofilms existed?
Since the origin of bacteria
Strange as bacteria have not evolved greater complexity
What is the difference between gram positive and gram negative bacteria?
Gram positive -> one membrane, on outer surface is thick coat of peptidoglycan
Gram negative -> two membranes, between membranes are molecules of peptidoglycan
Why is peptidoglycan essential for bacterial life?
Bacteria are stuffed with oncotic molecules
Puts turgor pressure on organism
Peptidoglycan prevents bacteria from bursting
How does Penicillin kill bacteria?
Penicillin weakens the peptidoglycan
Bacteria burst
How did LUCA form bacteria?
LUCA morphed into peptidoglycan containing cell
Primordial cell = cell with peptidoglycan containing wall
Evolution pushed the wall between two thin membranes or one thick wall
Do all bacteria contain peptidoglycan walls?
No
What are examples of a bacteria that does not contain a peptidoglycan cell wall?
Tenericutes - live on specialised niches like skin
Thermophiles - modified petidoglycan to overcome extreme conditions
What is endosymbiosis?
2 billion years ago non- and photosynthetic bacteria got into proto-eukaryotic cells
What did photosynthetic bacteria form?
Photosynthetic organelles in plant cells
What did non-photosynthetic bacteria form?
Mitochondria
Key for energy and apoptosis
Mitochondria benefits from being inside cells and cell benefits from having extra energy
What is neo-darwinism?
Modern take on Darwin’s theory of survival of the fittest
Neo-darwinism = mutations + genetic recombination
When plants and animals reproduce the offspring contains differences in DNA through genetic recombination
How are mutations selected for in Neo-Darwinism?
Mutations in DNA produce variations in proteins
Proteins can become favourable -> kept in gene pool, passed to offspring
Proteins can become unfavourable -> disappear from population
Why do bacteria have such low genetic recombination?
They reproduce clonally
What is the mechanism in which bacteria can have genetic recombination?
Plasmids
Bacteriophages
Genomic islands
Horizontal gene transfer - responsible for 30% of genes in bacteria
How does bacteria transfer DNA in order to allow for genetic recombination?
Naked DNA
Mechanisms of horizontal gene transfer
Transformation
Conjugation
Transduction
Describe the process of Transformation
Bacteria is taken up from environment via naked DNA and plasmids
Describe the process of Conjugation
Some bacteria perform sex
Tube between two cells
DNA transfer from one cytoplasm to another
Describe the process of Transduction
Bacteriophages - viruses infect bacteria
How many genes are there in a genome of bacteria?
3000
How many genes are there in a genome of a human?
19000
What is the pan genome?
Number of genes accessible for strain of bacteria
Does evolution happen at a constant rate?
Yes
Is the rate at which bacteria mutate constant?
No
HGT might be constant however
What is stress-induced mutagenesis?
Mutations can be enhanced if exposed to external stresses
What is an example of stress-induced mutagenesis?
Antibiotics drives antibiotic resistance
Bacteria mutate faster to increase resistance to antibiotics
How can plasmids be used to increase reisistance to antibiotics?
Bacteria can take up plasmids with antibiotic resistant genes
Makes organism into a resistant strain
How did bacteria evolve from LUCA?
LUCA -> bacteria
Initially bacteria lived in anoxic environment
Liquid and air - no oxygen
Cyanobacteria started producing oxygen
Planet becomes toxic
100s years -> atm contains oxygen
Bacteria living under different conditions evolve to these
