Microbes Flashcards
Why care about microbes?
- They make us sick
- they make us not sick ( bacteria in the gut microbiome help train our immune system and protect against pathogens)
3.They have been evolving for billions of years ( essential for all global nutrients cycles carbon, nitrogen, phosphorus)
- Continuing to evolve
Invisible world
Louis Pasteur(1870s): invisible microbes are responsible for fermentation, sepsis, and disease.
Social lives of bacteria: Symbiosis (living together)
- Symbiosis has played a big role in the evolution of life on earth
- Most plants and animals have microbiome: microbes living in and on them
- Humans are 2% bacteria by mass
The rise of cyanobacteria
Banded iron formations consist of alternating layers of flint and iron oxide. They formed when the oxygen content of the atmosphere was high enough to oxidize ferrous to ferric iron.
This was the result of the evolution of oxygenic photosynthesis.
Levels of biological organization
- Individual cell
- Population
- Community
- Individual cell
Mechanism: Metabolism and replication
Process: requires continual input of energy and material to keep the cell out of thermodynamic equilibrium
2.Population
Mechanism: variation and evolution
Process: replication causes variation; reproduction causes competition. Which means fitness increase
- Community
Mechanism: Consumption and nutrient cycling
Process: Populations are linked by consumption. Must be in mass and energy balance at level of ecosystem.
The boundary of the cell is the plasma membrane:
- The plasma membrane is a phospholipid bilayer
- It separates life from the environment
- Transport, signals, adhesion
The dual system of a cell
- The membrane of the cell encloses two distinct biochemical systems:
- Metabolism
- Information
- Metabolism
The cell generates or harvests energy and channels it to synthesize new biomass, including the components responsible for metabolism. Without a membrane the products of metabolism would rapidly diffuse away from one another.
- Information
The cell stores the information necessary to synthesize the metabolic system. Without a membrane the information system could not be permanently linked to the metabolic system.
Growth leads to reproduction
- Large cells are inefficient because volume increases faster than the surface area. Once the cell has grown to a certain size it divides to form 2 daughter cells. Both cells receive information and metabolic systems from the progenitor.
- Reproduction involves the division of biomass and the replication of information
Growth and Reproduction
- A more efficient metabolic system leads to more rapid growth and more rapid reproduction
- If the information system is coupled with the metabolic system by being enclosed in the same membrane, the increased efficiency is heritable
- The information that specifies a more efficient metabolic system will then itself be replicated more rapidly.
- This is called evolution by natural selection
Plasmids
Small DNA molecules that occur in bacteria but are not essential for normal function:
- They replicate at the same time as chromosome but daughter cells don’t always receive equal numbers
- Some plasmids encode conjugation that results in plasmid transfer from a donor to a recipient via pilus
- Plasmids may encode functions that benefit the host bacteria, but in some cases they are parasites
DNA replication follows the same basic scheme in prokaryotes and eukaryotes:
- but differs in many important details
- A protein ( DNA A ) recognizes origin of replication and unwinds DNA.
- Origin-binding protein loads 2 helices onto DNA
- ATP hydrolysis moves helicase along chromosome, driving a wedge between the strands and forcing
them apart - An RNA primer is synthesized on the single stranded portion of DNA
