week 4 - how small are microbes Flashcards
1
Q
the volume of a single cell of e.coli
A
- 1 um^3 (micron^3)
The weight - 80% of the cell is water
- Density of the cell is only slightly higher than water (5-10%)
- Water: 100g / L
- Mass of e coli = density x volume = 10^-12g
o Will not notice it
2
Q
consequences of microbes being so small
for them
A
- Air
o Don’t drop down - Water
o Coasting when stopping to swim
o Stopping dead immediately, flagellum more like a cork screw
o Balance between inertia and friction forces - Eating
o Sit there and food comes to them by diffusion
o Diffusion very fast on um scale (ms) but very slow on cm scale (days)
So important to understand diffusion
- Based in random movement
- E.g. random walk stay in same place
- So mostly going back on forth
- Staying in one place
- Going long distances is difficult
- Rely on diffusion for nutrients
3
Q
Consequences of being tiny for them
1. because they are tiny they
A
- Are simple single celled brainless creatures
- Cant buffer against environmental fluctuations / conditions
- Or actively seek their preferred habitat
- Have to adapt to the environments (follow from above)
- Grow (potentially fast)
- Reach vast numbers (1g of sugar makes 2.5 x 10^12 cells)
- Have high dispersal rates (transport) (can get everywhere)
- Have a high rate of evolution (can be in lots of different environments
4
Q
consequences of being tiny for them
2. microbes are masters of metabolism
A
- They have to be as they cant excel in much else and have to put up with the conditions they find themselves in (after dispersal)
- They can be as they evolve quickly and get into the tightest spots
- Many branches of the carbon/nitrogen/sulphur etc. cycles only carried out by prokaryotes
- Diversity of biochemistry and metabolic pathways is huge compared to eukaryotes
- They do all the decomposition and clean-up work (eating our pollution)
5
Q
A
6
Q
the nitrogen cycle
A
Nitrogen cycle is driven by microorganisms.
- No stage would happn without them
