BIOL 2460 Exam 3 Study Questions and Correct Answers
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Course
BIO 2460
Institution
BIO 2460
4 basic steps of bacterial reproduction 1. Growth of cell size & increase in cell components 2. Replication of DNA 3. Division of the cytoplasm (cytokineses) 4. Septum formation and division of daughter cells
Generation time time takes to double population
E. Coli generation time 20 minutes
B. S...
BIOL 2460 Exam 3 Study Questions and
Correct Answers
4 basic steps of bacterial reproduction ✅1. Growth of cell size & increase in cell
components
2. Replication of DNA
3. Division of the cytoplasm (cytokineses)
4. Septum formation and division of daughter cells
Generation time ✅time takes to double population
E. Coli generation time ✅20 minutes
B. Subtilis generation time ✅120 min
S. Aureus generation time ✅30 min.
M.tuberculosis generation time ✅15-20 hrs
Closed cultures have ___ resources ✅infinite
Culture density ✅the number of cells per unit volume
Lag phase ✅inoculum cells added and adjust to culture medium; no change in
population
Log/exponential phase ✅binary fission occurs; cell replication > cell death
Stationary phase ✅resources become depleted; cell replication = cell death
Death phase ✅endospores can form cell replication < cell death
Ways to measure growth ✅microscopic cell count, flourescent staining for alive & dead
cells, coulter count, viable cell count, optical density
Direct microscopic cell count ✅cells are counted under a microscope
Fluorescence staining ✅cells are counted under a microscope or flow cytometer
- red stains binds to damaged cells to indicate dead cells
Coulter counter ✅detects electrical resistance change due to cell denisty
- does not differentiate live/dead
,Viable plate counts ✅count of viable cells; samples are diluted and grown on solid
media
Results expressed in ___ ___ ___ per volume (CFU/ml) ✅colony forming units
Membrane filtration technique ✅known vol. Filtered through a membrane; membrane
plated and colonies counted
Most probable number (MPN) ✅statistical method used when counts are very low (<30
CFU/ml)
- water and food testing
Biofilm formation ✅micro ecosystem of one or more species that can provide
protection
Forms mainly in liquid environment
Biofilm structure ✅clusters of microbes in a matrix
Extracellular polymeric substances ✅secreted by organisms in the biolfilm
Hydrated polysaccharide gel with other macromolecules and channels
Biofilm formation step 1 ✅attachment of planktonic cells to a substrate
Biofilm formation step 2 ✅attachment becomes irreversible; cells become sessile
Biofilm formation step 3 ✅growth & division on substrate
Biofilm formation step 4 ✅production of extracellular polymeric substance (EPS)
Biofilm formation step 5 ✅attachment of secondary colonizers & dispersion of
microbes to new location
Biofilm formation is formed through ____ ____, or cell to cell communication ✅quorum
sensing
Normal biota in lungs is good or bad? ✅good
Plaque formation on teeth is good or bad? ✅bad
Main factors that affect growth ✅oxygen levels
Ph
Temperature
Osmotic pressure
, Barometric pressure
Is o2 always needed or tolerated? ✅no, many environments do not have 02
Optimal oxygen concentration ✅ideal concentration of O2
Minimum permissive oxygen concentration ✅The lowest concentration of oxygen that
allows growth
Maximum permissive oxygen concentration ✅The highest tolerated concentration of
oxygen
Obligate ✅must have
Facultative ✅can do both
Aerotolerant ✅tolerant
Aerobe ✅prefers O2
Anaerobe ✅prefers others than O2
Fluid thioglycolate medium ✅low percentage agar tube has a gradient of oxygen
Aerotolerance ✅determined by location of growth
Anerobic jars or anaerobic chambers _____ o2 ✅remove
Example of obligate aerobes ✅micrococcus luteus
Example of obligate anaerobe ✅bacteroides spp.
Example of facultative anaerobe ✅Staphylococcus aureus
Example of aerotolerant anaerobe ✅Lactobacillus
Example of microaerophiles ✅Campylobacter jejuni
Optimal growth ph ✅most favorable ph for growth
Minimum growth ph ✅lowest ph for growth
Maximum growth ph ✅highest ph for growth
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