Class notes
Growth and Culture of Bacteria
- Course
- Bio 250 (BIO250)
- Institution
- University Of South Carolina
These lecture notes go in depth about the growth and culturing of bacteria.
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Growth and Culturing of Bacteria• Microbial growth terms
o Microbial growth = # of cells
- not size! Asking about NUMBER OF
o Mother & daughter cells.
- original cell is the mother, the two creations are daughter cells
o Binary fission.
- mostly (Can find odd bacteria that reproduce by BUDDING)
- Both are ASEXUAL
o Budding.
- leaves scar tissue on outside of cell
- Tissue does not allow budding from same location
- Buds until entire surface is full
- Eventually dies because it can’t reproduce anymore
o Nutrient medium.
- TSA plate, TSB
- Different colors: different purposes
• Growth Phases
o Standard growth curve.
1. Lag phase: length depends on what condition the microbe was in before
2. Log phase: when you’re doing subculturing this is where you pull from: they grow much
faster than they are dying
3. Stationary Phase: growth rate equals death rate
4. Death Phase
o Usually on the order of hours or days.
o Most evident in broth cultures.
o Colonies on solid media are simultaneously in all phases.
• Factors Affecting Growth
o Physical
o pH
- add chemical buffers to keep cultures longer so pH doesn’t shift on them
o Temperature
- decrease temp. And slow growth rate
- Increase temp. To increase growth rate
o Oxygen
- obligate aerobes/anaerobes
- Facultative anaerobes
- Aerotolerant anaerobes
- Microaerophiles: Figure 6.15
o Moisture: every organism needs it
- Only eukaryotic thing that can survive without moisture is a spore
, - Resting cells, can be dried out
- Bacteria: endospores: can dry out
- Vegetative cells dried out die
o Hydrostatic Pressure: pressure increases the amount of pressure you are under by 2x for
every 10 meters of water you go down
- Barophiles live deep water, under pressure to keep enzymes folded properly
o Osmotic Pressure: red blood cells (erythrocytes) and salt, pressure of water pressing in on
cell or out from inside of cell
- Hypertonic:plasmolysis, isotonic, hypotonic:plasmocticis
- Halophiles: salt lovers: things that grow on your skin
o Radiation: smaller the wavelength, higher the energy, higher the energy, more damage
- Larger wavelength, less damage
- Phototrophs require radiation to survive (photoheterotrophs/photoautotrophs)
• The Measure of Success
o “That’s about right,” probably isn’t good enough.
o Quantification is key.
o Viable cells per unit volume or area.
- Cells metabolically active and capable of reproducing (cause infections)
- Grow in food products, produce toxins
o Methods:
▪ Serial dilution + plating
▪ Direct counts: hemocytometer: hemo (blood) Hemocyto: blood cell, Hemocytometer: measure
red blood cells
▪ Most probable number
▪ Filtration : applied with direct counts: great for environmental samples
- 2L water sample filtered to get all microbes out, stain, count
▪ Other: spectrophotometer
• Mudbloods Not Welcome
o Pure cultures are a must for laboratory studies.
o Solid media are a key tool.
▪ Thanks Dr. Koch & Mrs. Hesse!
o 1.5% agar melts at 95oC and solidifies at 40oC.
o Streak plate
o Pour plate
o Aseptic technique.
o Cultures are living things.
• Culture Media
o Natural media
Examples:
- water
- soil
- Animals, sticks
o Synthetic media
Examples:
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