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41 Cards in this Set
- Front
- Back
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How do prokaryotic cells divide? |
binary fission |
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What is binary fission? |
1 cell divides into 2... 2 cells divide into 4... 4 cells divide into 8.... and so on... |
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What is exponential growth? |
when the population doubles with each division |
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What is the significance of exponential growth in relation to bacteria? |
Because bacteria can duplicate so quickly they can have serious consequences when it comes to our health. For example, it only takes about 4 hours for 10 cells of a bacterial pathogen to become 40,000 cells. |
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What is generation time? |
The time it takes for 1 cell to become 2 cells (time it takes to double) |
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How can the generation time of E. coli be less than the DNA replication time? part 1 |
A cycle of replication will initiate before the end of the preceding cycle. This results in chromosomes with more than one replication fork.Multiple replication forks per chromosome allow bacteria to divide more rapidly than the replication cycle time. |
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How can the generation time of E. coli be less than the DNA replication time? part 2 |
Bacteria usually inhabit rapidly changing environments. The ability to divide faster than the genome needs to be replicated can be regarded as an adaptation to such environments, because it can be of great advantage to be able to perform cell divisions in short time when the conditions become favorable. |
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What is a biofilm? |
-Sometimes called "plankton," free floating prokaryotes attach to surfaces, divide, and release polysaccharides, DNA, and other polymers |
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What is the structure of a biofilm? |
-creates a mesh-like slimy film called: EPS (Extracellular Polymeric Substance) |
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What are the functions of a biofilm? |
1. Shields microbes growing within from disinfectants and antibiotics 2. Communicate and pass nutrients and waste through channels within biofilm 3. Interact with microbe communities (may be cooperative or competitive) |
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What are some examples of biofilms? |
dental plaque persistent ear infections |
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What are some advantages that biofilms have? |
-Can be cooperative or competitive to create favorable conditions for themselves -Can protect itself by shielding microbes |
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Where are some places that biofilms are found? |
1. digestive system 2. sewage treatment systems (can clog old pipes) |
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How resistant are biofilms to microbicides? |
1000x VERY |
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Biofilms are involved in _________% of infections? |
70% |
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Name some infections caused by biofilms: |
-catheters -heart valves -contact lenses -dental caries (cavities) |
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What is a pure culture? |
-A population of cells derived from a single cell -Allows study of a single species |
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What is aseptic technique? |
A procedure for performing tests in the microbiology lab that minimizes contamination |
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What is a closed system culture? |
-No new nutrients being added -No waste is removed |
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What kind of growth curve does a closed system yield? |
Characteristic growth curve |
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A closed culture is also called a __________ culture. |
Batch |
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What is an example of a closed culture? |
The tests that we do in lab using petri dishes. |
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What is an open system? |
-Continuous growth -Nutrients are added continuously -Waste is removed continuously by chemostat |
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What is another name for an open system? |
Continuous Culture |
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What is an example of an open system / continuous culture? |
We are - our GI tract |
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What is a streak plate? |
Simplest, most commonly used method for isolating a colony |
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What is the purpose of a streak plate? |
To obtain an isolated colony by creating areas of increasing dilution on a single plate. |
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How is a streak plate performed? |
Cells are spread out on a plate in order to separate them. Plate is divided into 4 quadrants. Quadrants 2, and 3 drag bacteria from the previous quadrant in order to dilute it out. Quadrant 4 (usually) does not. (Sterilization between each quadrant???) |
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Why do we do streak plates? |
It allows us to isolate a pure strain from a single species. We can also get a pure culture from a mixed culture this way. |
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Bacterial Growth Curves: What happens in the LAG phase? |
-# of cells does NOT increase -cells begin synthesizing enzymes required for growth -Delay depends on conditions |
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Bacterial Growth Curves: What happens in the LOG (Exponential) Phase? |
-Cells divide at a constant rate **Generation time is measured -Cells are sensitive to antibiotics -There are primary & secondary metabolites (products of metabolism) |
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Bacterial Growth Curves: What IS a primary / secondary metabolite and why are they significant? |
-the intermediates & products of metabolism Primary - involved in growth, development, and reproduction of the organism. Secondary - not involved in growth / development...formed near end of growth phase |
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Bacterial Growth Curves: What are the primary & secondary metabolites of the LOG (Exponential) phase? |
Primary: amino acids
(important commercially...) Ex. alcohol, amino acid supplements Secondary: production occurs as nutrients are depleted and wastes accumulate (antibiotics) |
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Bacterial Growth Curves: What is happening during the Stationary phase? |
-Nutrient level are too low to sustain growth -Total #s remain CONSTANT (Some die, release contents, others grow) |
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Bacterial Growth Curves: What happens during the Death Phase? |
-Total # of viable cells DECREASES -Cells die at a CONSTANT RATE -Death is exponential, but usually much slower than cell growth. |
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Bacterial Growth Curves: What happens during the Phase of Prolonged Decline? |
-Survival of the fittest --> -Some may survive -Adaptation to tolerate worsened conditions ("Darwin Phase") per Dr. Decker (mutations antibiotic resistance, etc.) |
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Would you see this typical growth curve in an open system culture or closed system culture? |
CLOSED |
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During which phase are primary and secondary metabolites produced? |
LOG (Exponential) phase |
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During which phase re bacteria most sensitive to antibiotics? Why |
LOG (Exponential) phase -Because they are new, "baby" cells that have not yet fully equipped themselves for protection...therefore they are sensitive. Lots of new cells being produced at this stage. |
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During which phase is Natural Selection experienced? |
Phase of Prolonged Decline |
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What are the major environmental conditions that will affect prokaryotic growth? (Physical & Chemical) |
Physical: Temperature pH Osmotic pressure Chemical: Carbon Oxygen Nitrogen, Sulfur, Phosphorus Trace Elements Organic growth factors
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