Small Is Beautiful - Lecture Flashcards
Smallest bacterium identified to date
Candidatus action Marina minuta
Mycoplasma
X
Average size of a spherical bacterium
0.5-2 micrometres
Why cant bacteria get any smaller?
Need enough volume to accommodate genetic resources
Machinery needed to express genes and housekeep proteins/biochemicals
Smaller cell means (SA:V)
Higher SA:V ratio
As cell size increases the SA:V …
Decreases
What happens if a cell gets too big?
Not enough material can cross the membrane fast enough to suffice what’s needed now the volume has increased.
Then the cell must divide into smaller cells with more favourable SA:V
What is the importance of SA:V?
How fast a cell can grow depends on the rate at which it can exchange waste products and nutrients with the environment. If it has a higher SA:V it can do this quicker.
A large population of small cells can be better supported than a population of large cells.
Example of giant bacteria (big but with huge energetic cost)
E. Fishelsoni (found in the guts of surgeon fish)
- extreme polyploidy (possessing more than two complete sets of chromosomes)
Advantage of being an extremely small bacteria
Enormous SA:V which may be advantageous to obtain nutrients in resource deficient habitats
Disadvantages of being an extremely small bacteria
Genome very small - genes encoding enzymes for core metabolic pathways are not present - metabolically limited lifestyle (evolutionarily limited)
What are the three major functions of the cytoplasmic membrane?
- Permeability barrier - highly impermeable and most subastances carried in or out are carried by transport proteins
- Protein anchor
- Energy conservation and consumption - membrane involved in creating proton motive force and electrochemical gradients
Three ways a substance can be transported through a cell membrane
- Simple diffusion
- Facilitated diffusion
- Active transport
Simple diffusion example
Small non-polar molecules such as oxygen or carbon dioxide
Facilitated diffusion example
Larger charged molecules such as chloride or sodium ions
Binary fission definition
Asexual reproduction in unicellular prokaryotic organisms by separation of the body into two new bodies
6 steps of binary fission
- Cell elongates
- Bacterial genome replicates + any plasmids also replicate
- Duplicated DNA separates and moves towards poles as the cell elongates
- Cleavage furrow forms
- Cell wall forms in cleavage furrow
- Two identical daughter cells are formed
4 main differences between mitosis and binary fission
MMPD
Mitosis in multicellular organisms, BF in unicellular organisms
Mitosis has mitotic spindles, BF does not
Mitosis has subphases (prophase, metaphase, telophase, anaphase), BF does not
DNA replication occurs in S phase in mitosis, in BF it occurs at the same time as binary fission
Three reasons binary fission is decent
Only one parent required to reproduce
Rapid division
Daughter cells are clones of parent cells
Photoautotroph
Uses light as an energy source
Can fix carbon from non biological sources
Photoheterotroph
Using light as energy source
Organism must obtain carbon from biological sources
Chemoautotroph
Organism uses chemical reactions as energy source
Organism can fix carbon from a non-biological source
Chemoheterotroph
Organism uses chemical reactions as an energy source
Organism can obtain carbon from biological sources
Prefix for energy form light
Prefix for energy form chemical reactions
Photo
Chemo
Autotroph
Organism produces own food using light, water, carbon dioxide or other chemicals
(Producer)
Heterotroph
Organism eats other plants and animals for energy and nutrients
Most prokaryotes are …
Chemoheterotrophs
Many break down organic waste/play roles as decomposers etc
What are photoautotrophs important in?
Aquatic ecosystems
What are cardinal temperatures?
Minimum temperature below which growth isn’t possible
Optimum temperature at which growth is most rapid
Maximum temperature at which growth is not possible
Four broad classes of microorganisms based on optimum growth temperatures
Psychrophile
Mesophile
Thermophile
Hyperthermophile
Talk about mesophiles (4 things)
- Widespread - found in digestive tract of animals, terrestrial and aquatic environments, temperate and tropical latitudes
- E. Coli is a typical mesophile
- Majority of bacteria associated with humans are mesophiles
- Optimum temperature = 39 degrees
Talk about psychrophiles (3 things)
- Optimal = 15 degrees or lower
- Found in constantly cold environments
- Often grow in dense masses within and under sea ice in polar regions
Psychrophile enzymes
Produces enzymes that function optimal in colder temperatures
Psychrophile membrane
Membrane remains du toon despite cold temperatures because it’s semi fluid state is maintained by membrane having a higher content of unsaturated and shorter fatty acid chains
Psychrophile cold shock protein
Type of molecular chaperone which can maintain cold- sensitive proteins in an active form
Psychrophile cryoprotectants
Cryoprotectants help prevent formation of ice crystals which can puncture the cytoplasmic membrane
Eg. Antifreeze proteins, glycerol, exopolysaccharide cell surface slime (creates slime layers that offer protection).
Thermophile (3 things)
- Optimum temperature 45-80 degrees
- found in hot springs, deep sea hydrothermal vents, decaying plant matter
- source of thermos table enzymes used in PCR
Hyperthermophile
- Optimum temperature exceeding 80 degrees
- most tolerant known = methanopyrus (archaea capable of growth up to 122 degrees)
Further thoughts slide
What is the significance of finding extremophilic prokaryotes?
What might be the consequences of this diversity for life of earth?
Could we live without prokaryotes?
