Lecture 2 Notes (Part 3) Flashcards
Primer
Is a short strand of RNA or DNA that serves as a starting point for DNA synthesis
What is required for DNA replication and why?
- Primer
- Because the enzymes that catalyze this process (DNA polymerase) can only add new nucleotides to an existing strand of DNA
How many nucleotides typically make up a primer?
20
What is a major advantage for quantitative PCR and molecular probing? (2)
- Can be very specific
2. Does not require growth
What is a community?
- Whittaker, 1975
A system of organisms living together and linked together by their effects on one another and their responses to the environment they share
What is a community?
- Ricklefs and Miller, 2000
The many population of the many different organisms that we see in a particular place and that are tied to one another by feeding relationships
Neutralism
Lack of interaction between 2 populations
When is neutralism more likely to occur? (2)
- Between populations with extremely different metabolic capabilities
- Populations that are spatially distinct from each other
Commensalism
An association between two organisms in which one benefits and the other derives neither benefit nor harm
Synergism
2 populations are both benefiting from the relationship but when the relationship is NOT obligatory
What do methanogens produce? How?
Methane from fermentation of acetate or reduction of CO2 with H2 from the oxidation of propionate or butyrate and caproate
What do methanogens provide? What does it allow?
- H2 sinks for syntrophic bacteria
- Allows for counting of growth
- if too much H2 it will shut down
Mutualism (symbiosis)
Obligatory relationship between 2 populations that benefits both populations
What are 2 examples of mutualism?
- Lichens with a fungus
2. Mycobiont provides support and nutrient transport to phycobiont
Competition
A negative relationship between 2 populations in which both populations are adversely affected with respect to their survival and growth
When does competition occur?
When 2 populations use the same resources, which limits nutrients and space
Competitive exclusion principle
2 populations cant occupy exactly the same niche or use the same resources
What is the typical result of competition?
1 population will win the competition and the other will be eliminated
How can a population avoid direct competition?
By using different resources at different times
How can competition be assessed?
Experimentally between pure cultures
Amensalism
Microorganisms that produce substances toxic to competing population will naturally have a competitive advantage
What are 2 other names for amensalism?
- Allelopathy
2. Antibiosis
Allelopathy
The chemical inhibition of one plant (or other organisms) by another, due to the release into the environment of substances acting as germination or growth inhibitors
What 2 things are inhibitory to many bacterial populations?
- Production of lactic acids
2. Low molecular weight fatty acids
What does production of sulphuric acid by Thiobacillus thiooxidans do?
Lower the pH and cause acid mine drainage which prevents growth of other microorganisms
What prevents growth of bacteria?
Production of antibiotics
What is nisin produced by and what does it do?
- Produced by some bacteria
2. Disrupts cell membrane properties
Parasitism
The population that benefits (parasite) derives its nutritional requirement from the host, population which is harmed
Ectoparasites
A parasite that lives outside the cells of the host population
What is an example of an ectoparasite?
A flea
Endoparasites
A parasite that lives inside the host cell
What us an example of an endoparasite?
A tapeworm
What are viruses of bacteria called?
Bacteriophages
How do viruses form parasites? (4)
- Viruses dock at the bacterial cell surface
- Injects its DNA (which is first replicated)
- Proteins are synthesized
- Precipitate around the viruses genome to form parasites
When does predation occur?
When one organism, the predator, engulfs and digests another organism, the prey
Selection
Microorganisms must extract energy efficiently and matter from the environment in order to grow and transfer genetic material to offspring
R-strategist
Success may be related to better molecule machinery for macromolecule synthesis
K-strategist
Success may be related to a better use or a more efficient extraction of the energy and matter in the immediate environment
What happens to the population when the density is low?
The rate of population changes and is dominated by r
What happens to the population when the density is high?
The growth rate is dominated by k
