Lecture 28 Flashcards
Why are prokaryotes so dominant?
Fast growth rate (13 min doubling time) = evolve/adapt fast
- linear relationship between the size of an organism and how fast they replicate (core)
- they are very old so have adapted to many environments thus colonising most habits with their extreme ecological and metabolic activity (not core slide)
How does the process of binary fission work?
- from one cell to two
- Chromosome (single and circular) replication begins - copying the genome
- One copy of the origin is now at each end of the cell and call begins to divide
- Replication finishes
- Two daughter cells result
How do prokaryotes reproduce?
Prokaryotes reproduce asexually by cell division through the process of binary fission.
Binary fission results in the formation of two cells that are genetically identical.
Composition of microbial cells
- not much different than eukaryotic cells in their cellular requirements
- microbes need the same building blocks as us, just different amounts
- if we supply them with all required materials they can reproduce
Classic way of growing microbes: closed batch culture system
- refers to a form of cell culturing
- defined (limited amount) supply of nutrients is provided
- once used (become limited) cells cannot proliferate
- standard method of studying microorganisms in culture
- dictated by method not shape of flask
Microbial growth: “feast and famine” - 4 stages of microbial growth cycle in the lab
Lag phase = length depends on history of the inoculum time, time is required to get biosynthetic reactions running
Exponential phase (log phase) = cells are actively dividing and nothing is limiting for growth - populating is doubling in a constant time interval (under ideal conditions).
Stationary phase = cells stop growing (run out of nutrients) and cryptic growth is observed (amount of cells growing = amount of cells dying) - they can also make nasty end products that inhibit growth
Death phase = cell death, equilibrium between growing cells and dying is skewed towards death (very small amount survive sometimes)
‘Closed’ batch culture system
- easy lab model, but biased towards fast growing organisms like pathogens
What is cryptic growth
- When organisms survive by consuming lyses cell constituents of dead cells within the culture
- this is not a static population but a dynamic population. There is an equilibrium between growing and dying cells
Are all cells created equal?
- some cells behave differently
- batch culture assays measure the average behaviour of cells
- no growth means death rate and growth rate in balance
What do prokaryotes need to multiply
Microorganisms need three things to grow:
- Carbon Source:
- building blocks for macromolecular synthesis (microbes harvest carbs from autotrophs as sources of carbon/energy) - Energy Source:
- energy (electrons) to drive anabolic and catabolic reactions in the cell (transform light energy into carbs, NADPH and ATP) - Reducing Power
- carriers of energy/electrons (NAD+/NADP+)
- nicotinamide adenine dinucleotide (NAD)H = reduced form
All reactions are coupled together just like in plant, mammalian and bacteria cells
How do prokaryotes harvest energy?
Molecules = natures batteries
- chemical energy stored in bonds
- broken chemical bonds release energy that can be captured in new bonds (ATP)
- ATP = most common energy currency
- ATP bonds can be broken again later to release that energy
- this reduction and oxidation of coupled compounds can be applied to many compounds and forms the basis of ‘redox reactions’
(- bacteria form pyruvic acid, ATP and NADH from splitting glucose (how the energy get harvested) (from lecture talking))
Simple transformation —-> big repercussions
- subsatrates turned into monomers
- some carbon (monomers - building blocks) from the conversion of substrates to produces are taken and used for anabolism (energy consumption) to make other macromolecules and other cellular constituents
- the energy from anabolism comes from catabolism - the energy released when the substrates are broken down
Tropic (nourishment) groups in microbiology. (NOT CORE SLIDE)
- can characterise bacteria depending on the nourishment that they get
- only two ways they can generate energy:
- light
- chemical compounds
- only two carbon sources
- carbon dioxide (auto) - self built
- organic compounds (hetero) - feeding on others
Chemoheterotrops
Chemoautotrops
Photoheterotrophs
Photoautotrophs
Limitations to pure cultures when studying communities - WILD TYPE STRAIN
(- bacteria either needs to be either given the nutrients required
- or it needs to be able to synthesise its own nutrients you dont need to add )
WILD TYPE
- has all the essential genes
- can grow by itself
- can be isolated into pure culture
- EG Leucine biosynthesis
- able to synthesise required nutrients (amino acids)
Limitations to pure cultures when studying communities: AXOTROPH
- lacks or is defective in one or more essential genes
- cannot grow unless missing factor is supplied
- EG: LEUCINE
Cross feeding =
also called syntrophy, is when one species gains metabolic products of another species
