Lecture 8: Bacterial Cultures and Growth Flashcards
Explain how bacterial cell division differs from eukaryotic cell division.
Bacterial cells divide via binary fission producing daughter cells that are isogenic (contain the same genetic material).
Describe a biofilm, and explain the stages of biofilm formation.
Bacteria become specialized and work together to begin the stages of formation. They lose flagella, adhere to surface (fimbriae and glycocalyx), grow and divide, differentiation (become specialized), when the inside of the biofilm can no longer get enough nutrients, the cells will become free swimming individual cells (plankton).
Explain what it means to say that a bacterial colony is clonal.
The colony is isogenic meaning all the daughter cells have the same genes.
Understand why it is helpful, but not absolutely necessary, to isolate a bacterial colony before studying the growth and physiology of the cells.
It is helpful to separate cells if you want to study one individual bacteria cell. But, it is not necessary because we can put a single cell in a nano chamber and study it (do not need a colony).
Describe 3 ways to store bacterial cultures long-term.
- Put in cryoprotectant and then freeze them. The cryoprotectant prevents H-bonding of H2O molecules.
- Lyphophilize by freeze drying them in to pellets. This works better for gram positive rather than gram negative bacteria.
- Agar slants can be used to store them because agar doesn’t dry out as quickly.
List 5 categories of bacteria based on optimal growth temperature.
1-Psychrophiles: Lowest temp; optimal around 10-15 degrees. Produce antifreeze proteins and contain more unsaturated lipids.
2-Psychrotrophs: Optimum around 15-30 degrees (room temp).
3-Mesophiles: Optimum around 30-40 degrees (body temp).
4-Thermophiles: Optimum around 50-85 degrees. Saturated lupus keep membrane from melting.
5- Hyperthermophiles: Sometimes above boiling point and has more ionic bonding. Optimal between 90-110 degrees.
Sketch a typical graph of bacterial growth rate vs. temp. and explain the shape of the graph.
Off centered bell curve that peaks nearer to the high temperature because bacteria prefer warmer temperatures.
List five categories of bacteria based on oxygen requirement.
- Obligate anaerobe
- Aerotolerate anaerobe
- Obligate aerobe
- Faciltative anaerobe
- Microaerophile
Recognize how to distinguish between these 5 types in the lab.
Thioglycollate tubes and shake tubes will grow bacteria in particular locations on the tube depending on how much oxygen they need.
1-Obligate anaerobe: Completely at the bottom.
2-Aerotolerate anaerobe: Spread evenly throughout tube.
3-Obligate aerobe: Completely at the top.
4-Faciltative anaerobe: More concentrated toward the top but spread evenly.
5-Microaerophile: Nearer to the top but relatively in the middle.
Explain the differences in metabolism between the 5 categories listed above.
1-Obligate anaerobe: Don’t use any oxygen because oxygen is toxic to them. Uses fermentation.
2-Aerotolerate anaerobe: Can tolerate O2 by having superoxide disputes that detoxifies O2.
3-Obligate aerobe: Needs O2; depends on respiratory chain and can not do fermentation.
4-Faciltative anaerobe: An aerobe that can also be an anaerobe. Has the ability to use fermentation but usually uses respiratory chain.
5-Microaerophile: Needs O2 but doesn’t have the means to detoxify it. Usually buries to a location containing about 1% oxygen.
List 3 categories of bacteria based on optimal pH for growth.
1-Acidophile: Lots of protons causing too much of a pmf. Must switch membrane potential (+ inside) and have really active proton pumps.
2-Neutrophile
3-Alkalophile: Have too small of pmf and use sodium ion gradients to pump protons into the cell.
Explain two ways in which bacteria prevent plasmolysis in a hyperosmotic environment.
- Osmoprotectants balance osmotic pressure.
2. Halophiles have charges on proteins to absorb ions. There must be salt in the environment or the proteins will lyse.
List 10 elemental nutrients required for bacterial growth, and explain where bacteria get these nutrients and what cell structures the nutrients are used to build.
C, H, O, N, P, S,
K+, Mg^2+, Ca^2+
—Use charge shielding in order to fold proteins.
Fe^2+
—Electron donor/acceptor and involved in redox reactions.
List the metabolic categories that explain how bacteria obtain carbon, energy, and electrons.
1-Chemotroph: Free energy change of redox reactions.
2-Phototroph: Sunlight (photosynthesis).
3-Heterotroph: Organic compounds.
4-Autotroph: CO2.
5-Organotroph: Reduced organic compounds.
6-Lithotroph: Reduced inorganic compounds.
Be able to categorize a medium as complex or defined based on an ingredients list.
Complex mediums are where one of the ingredients is not defined because either the quantity is not specified or it has no specific chemical formula (blood).
Defined mediums have all the ingredients defined.
