introduction to prokaryotes: Unit 3, Chapter 12
Prokaryotes
- Small and structurally simple
- 1-3 micrometers across
- No nucleus; one chromosome
- No internal membranes
- Oldest known fossils are most likely prokaryotes
- Microbial mats - 3.5 BYA - multilayer sheet of prokaryotes
- stromatolite - sedimentary structure formed as minerals are precipitated out of water by prokaryotes
- Eukaryotes thought to have arisen through evolution from prokaryotes
Universal ancestry
- Domain eukarya
- Domain archaea
- Euryarchaeotes
- Crenachaeotes
- Nanoarchaeota
- korarchaetoes
- Domain b
- Probactira
- Chlamydais
- Spirochetes
- Cyanobacteria
- Gram-positive bacteria
Habitats of prokaryotes
- everywhere
- Soil
- Water
- Bodies of other organisms
- Ice
- Rocks
- Hot springs
- Salt lakes
- Seafloor
- Underground
- ect.
Culturing prokaryotes
- Koch and petri
- Culture method still used today
- Koch's postulates-infected samples, healthy samples, re infection
- Non culturable prokaryotes
- 99% of prokaryotes - unknown conditions - DNA, PCR, NGS
- Viable but non culturable state - previously cultured - stressed
- Resurrection- goes back to normal state with improved conditions
Biofilms
- Microbial community held together by gummy substance (EPS, exopolysaccharide substance)
- Protects prokaryotes from environment
- Cells within biofilm communicate and collaborate with each other
- Difficult to remove, difficult to kill
- Large (visible to naked eye) thick biofilm: “microbial mat”