Key Terms
Binary fission
Primary reproductive mechanism in bacteria; asexual; produces two identical daughter cells.
Sequence of events
1. Cell grows; increases cellular components 2.
FtsZ
Protein that assembles into the Z ring on the cytoplasmic membrane; initiates division.
Generation time (bacteria)
Time for population to double through one round of binary fission. Also called doubling time.
Formula
Nn = N0 x 2^n
Example
S. aureus quorum sensing triggers enzymes that degrade human tissue; allows spread to nutrient-rich areas.
Batch culture (closed culture)
No nutrients added; waste not removed. Four distinct phases result.
Chemostat
Continuous culture vessel maintaining log-phase growth.
Example calculation
10 cells in a square with volume 0.000008 mL = 1,250,000 cells/mL.
Pour plate method
Sample mixed in warm liquid agar (45-50 degrees C); poured into Petri dish; swirled; incubated. Spread plate method: sam
Membrane filtration
Vacuum filters dilute samples through membrane; membrane transferred to agar; colonies counted; used for very dilute sam
MPN method
Statistical estimate for very dilute samples; no solid media required.
Fragmentation
Filamentous cells or cyanobacteria accumulate multiple nucleoids; segments break off; each becomes new cells. Common in
Budding
Extension grows from one pole; tip swells into a smaller cell (bud); bud detaches. Most common in yeast; also in prosthe
Epulopiscium (giant bacterium)
Daughter cells grow fully INSIDE parent cell; parent disintegrates releasing them.