Prokaryotes
- Microscopic organisms contributing to global biomass
- Highly adaptable and thrive in diverse environments (ranges from human gut to deep underground or acidic lakes)
What is a prokaroyte?
- Earth’s earliest life forms, and evolved into two distinct domains: Archaea and Bacteria
- Both domains share a common ancestor and possess a simple, prokaryotic cell structure
qualities of a prokaryote
- Prokaryotes are typically small and unicellular
– This allows for rapid metabolism but limits their potential size - They can be various shapes: spheres, rods and spirals
- Prokaryotes lack a nucleus; their circular genome is free in the cell
Structural and Functional Adaptations Contributing to Prokaryotic Success
- Cell Surface Structure
-Endospores - Motility
- Simple Internal Organization and DNA
Peptidoglycan
- a network of sugar polymers cross linked by short peptides
- present in bacterial cell walls but NOT Archaea cell walls
Gram positive bacteria
- have simple cell walls with thick peptidoglycan layers which allows them to retain a crystal violet stain
Gram negative bacteria
have thinner peptidoglycan and an outer lipopolysaccharide membrane
lipopolysaccharide
- an outer membrane that adds complexity to the cell structure and serves as a protective barrier
capsule
a sticky layer of polysaccharides or proteins
that help prokaryotes stick to surfaces as well as each other forming an adhesive biofilm
fimbriae
short, hair-like structures that help cells adhere to surfaces
pili (or sex pili
long and allow for DNA exchange between prokaryotic cells. This enhances genetic diversity
Endospores
- Form when environmental conditions become unfavourable (i.e. extreme temperatures or a lack of nutrients).
- Have tough, protective coatings protecting them from heat, chemicals and radiation.
Motility
Half of prokaryotes are motile which means they can actively move. They use flagella for movement.
Flagella
- Whip-like appendages that are distributed across the cell surface or concentrated at one or both ends of the cell.
- Can move some species 50 body lengths per second
Simple Internal Organization and DNA
- simple internal structures without any complex compartmentalization
- Lacks membrane enclosed organelles
- Have small genomes which are defined by a single circular chromosome
binary fission
- asexual reproduction
- produces genetically identical copies of the original cell
Rapid reproduction
frequent divisions resulting in many generations in a short time
Mutations in Prokaryotic Cells
- Since reproduction produces daughter cells which are typically IDENTICAL (a clone), The mutation rates during binary fission are low but their rapid reproduction rate allows them to accumulate quickly in populations
Genetic Recombination
- A process in which genetic material is exchanged between individual cells
- Occurs through: transformation, transduction, conjugation
Transformation
Bacteria takes up and combines DNA from their external environment
Transduction
The transfer of DNA through bacteriophages
