What are the 4 reasons for studying prokaryotic genetics?
- Provides a basic understanding of molecular biology + genomics and where research came from etc
- Bacteria fundamental to human health + disease so understanding of genetics = important
- Bacterial ecology; what bacteria are in environment, how do they interact etc.
- Applications to biotechnology; manipulating bacteria for human uses.
History of genetics - who was involved and when?
- Lamarck, 1800 -> species aren’t fixed.
- Darwin, late 1800s -> “Origin of species”
- Beadle and Tatum 1941 -> “One gene, One enzyme”
- etc
2003 = human genome project -> current = post genome era.
What is the definition of bacterial genetics?
Bacterial genetics = study of mechanisms of heritable information in bacteria.
What are the 4 mechanisms studied in bacterial genetics?
Studying:
- Chromosomes
- Plasmids
- Transposons
- Phages
What techniques can be used to study bacterial inheritance mechanisms?
Techniques:
- Culture in defined media
- Replica plating, mutagenesis, transformation, conjugation and transduction
ALL = methods of moving genes around.
What is the abundance of bacteria in the world?
30% of DNA on earth = bacterial
Vast majority of organisms = archaea or bacteria etc (single celled organisms)
Spread of cells in the body eukaryotic vs bacterial?
Aprx bacterial cells = eukaryotic cells in body.
What are the 6 factors that make bacteria model organisms ?
- Haploid = one gene for everything means easy study
- Asexual reproduction = cell division creates identical daughter cells meaning easy to workout reproduction
- Short generation time = useful in research
- Growth in defined media for some = full control of nutrients means defining metabolic pathways
- Easy to store
- Easy to genetically mutate
What does bacterial genome look like?
- Single, circular double stranded DNA chromosome
What bacterium’s chromosome is the exception?
Borrelia burgdorfei (limes disease causer) -> Single linear chromosome.
What is a bacterial genome size?
Varies hugely - 0.58 mega base pairs => >10 mbp
What is special about the bacterial genome?
- Little space in-between genes (more % overall are gene coding versus eukaryotic genomes)
- Lack of introns (unlike eukaryotes)
- Genes grouped into operons
- Often carry plasmids
What are operons?
Genes with related functions grouped together under one promoter
What are plasmids?
Plasmids =
small circular DNA that replicates independently.
often w extra genes important for e.g. antibiotic resistance etc.
E. coli genome in detail - How big?
EC => DNA = 1mi long
Same thickness as spiderweb
How do bacteria reproduce?
Via asexual reproduction
Cell elongates and content volume is increased
The cell divides into two => creates identical daughter cells w copy of plasmids and DNA in each cell.
3 essential steps in bacterial reproduction
- Cell grows to 2x length
- Septum then forms in middle
- Cell grows from either end then pinches to break cell into 2.
Why is generation time important?
- Many bacteria are fast to replenish and divide. (EC = 20mins)
- Some are 1000s of years or unable to be cultured but vast majority are useful.
What affects generation time?
Optimum conditions = fastest growth time.
Conditions:
Nutrients
pH
Temperature
etc
What is needed to grow EC?
1940s = modern model organism
Synthesises all own cellular components using inorganic nutrient + carbon.
- Able to grow on really defined media. => useful for metabolism and growth studies
EC minimal media with glucose - composition?
Phosphates -> pH control + phosphate source.
Nitrates -> source of nitrogen
Magnesium -> useful for nucleotides + proteins.
Calcium chloride -> useful for sensing + membrane transport
Trace metals -> important for protein function
Glucose -> a carbon source + used for energy
What is the point of growing EC on minimal media?
Looking for mutants that won’t grow without certain nutrients.
What is a prototroph?
Wild type EC = doesn’t need any nutrients. => can grow on minimal media
What is an auxotroph?
Mutants of a wild type that now require certain nutrients to be able to grow => can no longer grow on minimal media.
