What are Properties of ALL cells?
- Metabolism (take up nutrients, transform and then expel waste)
- Growth (nutrients taken up - converted to new cell materials to form new cells)
- Evolution (Cells evolve to display new properties)
What are Properties of SOME cells?
- Differentiation (some cells form new cell structures e.g. spores)
- Communication (via chemical messengers(
- Genetic Exchange
- Motility (self propulsion)
Differences between Prokaryotes and Eukaryotes
Prokaryotes
- No Nucleus
- Nearly all have cell wall
- No organelles
Eukaryotes
- Some have cell walls, some don’t
- Membrane bound nucleus
- Generally larger than prokaryotes
What are the different shapes Prokaryotic cells form?
- Cocci - sphere-shaped
- Rod/Bacilli - cylinder shaped
- Spiral/Spirilla - curved rods to tightly coiled bacteria
- Appendaged Bacteria - cells have extensions like stalks or hypha
- Filamentous - connected chains of cells (usually cocci or bacilli)
- Other: square/star sharped, are very rare
Most common prokaryotic shape
Bacilli/Rod shaped
How do Cocci cells arrange themselves to be easier to ID?
Arrange over varying numbers of planes
- Dip- is 1 planes
- Strep- 1 planes in a chain
- Tetrad - 2 planes
- Some are random such as staphylococci
Normal measurements of prokaryotes
0.5-2 um diameter and 1-5 um in length
What is the advantage of smaller size?
Microbes absorb nutrients through their cell membrane - smaller cells have a greater surface to volume ration and therefore absorb more nutrients proportional to their demand
Where do Microbes Live?
Everywhere
water, land, extreme environments and in gut flora of animals
Describe the properties in water that different prokarotes thrive in
Bacteria - more prevalent close to surface where O2 and Temperature are higher
Archaea - deeper where there is lower temp/O2, use H2S for energy instead of heat/light
Where are microbes found in land?
In sediments and deep subsurface
- esp in organic material in fertile soil and sediments
- Near Groundwater usually
What role do microbes play in normal gut flora?
Important for immune development, behaviour, health and disease prevention
How do we know where microbes live?
Sample testing
Microbes live in communities and undergo symbiotic interactions - describe these interactions
Positive:
- Mutualism
- Synergism
- Commensalism
Negative
- Parasitism
- Predation
Describe the symbiotic relationship: Mutualism
Both require and benefit
e.g. lichen, gut microbiom
Describe the symbiotic relationship: Synergism
Both benefit but don’t require
e.g. skin microbiota
Describe the symbiotic relationship: Commensalism
Only one benefits
e.g. cross-feeding
Describe the symbiotic relationship: Predation
E.g. protozoa/bacteria
Absorbs other microbe for nutrients, killing it
Describe the symbiotic relationship: Parasitism
E.g. viruses/pathogens
Uses host cell for functions
When did first prokaryotic micro organisms evolve?
3.8 billion years ago
What did the Miller-Urey experiment demonstrate?
That early earth atmosphere (reducing and lacking O2) was an environment that organic molecules (amino acids, sugars, nucelotides and fatty acids) could be synthesised in
- In presence of heat and electricity (high energy)
What is the RNA theory for the origin of Life?
First self-replicating organisms thought to be made of RNA
Describe the RNA theory for the origin of life (sequence of events)
RNA formed from pre-biotic compounds –> riboenzymes could self-replicate and carry out reactions (catalysis) –> became enclosed in lipid vesicles
- -> Amino acids entered vesicles that enclosed RNA –> Proteins synthesised –> carry out catalytic activity in early cells –> more proteins –> more reactions
- -> RNA eventually developed into DNA
What is the subsurface hypothesis or the origin of life?
Life likely developed subsurface
