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45 Cards in this Set

  • Front
  • Back
What are the five steps of Binary fission?
1) DNA Replication

2) Cell Elongation

3) Septum Formation

4) Formation of Distinct cell walls

5) Cell Separation
Fts Proteins (Filamentous Temperature Sensitive)
cell division dependent on this

interact to form a "divisome"
Division apparatus in the cell

orchestrates synthesis of new cytoplasmic membrane and cell material in both directions until the cell reaches twice its original size
How is the divisome formed?
formed by FtsZ proteins in a ring around the cell center

FtsA, FtsI, and ZipA are attracted to the ring structure and associate with FtsZ
DNA replication occurs prior to what?
FtsZ ring formation
helps to pull apart daughter cells following elongation
Min Proteins (Min C and Min E)
assist FtsZ in finding precise center of the cell
What are three characteristics of MreB?
1) the major shape determining protein in prokaryotes

2) very similar to actin protein in eukaryotic cells

3) not found in coccus-shaped bacteria (default shape is spherical)
Autolysic enzymes
in divisome complex

create openings in the cell wall so that peptidoglycan can be distributed between daughter cells
What does autolysin cut to make new peptidoglycan?
It cuts pre-existing peptidoglycan and inserts peptidoglycan precursors (such as muramic acid and glucosamine)
lipid carrier molecule that helps in the insertion of glucosamine and muramic acid in new peptidoglycan

transports precursors across cell membrane for incorporation into the growing point of the cell wall
Final step of cell wall synthesis

formation of peptide cross links between muramic acid residues in adjacent glycan chains
inhibits transpeptidation

binds to Fts proteins and render them catalytically inactive
Generation time
the time required for cell population to double
Exponential growth
when the number of cells doubles during a regular time interval
What are the four phases of exponential growth?
1) Lag Phase

2) Exponential Phase

3) Stationary Phase

4) Death Phase
Lag Phase
may be brief or extended depending on history of culture and growth factors
Exponential Phase
may be brief or extended depending on nutrients

smaller cells grow faster than larger cells
Stationary Phase
do not increase or decrease in cell number

essential nutrients being used up and waste products are accumulating
Death Phase
Cells begin to slowly die off
How is microbial growth measured?
measured by the change in the number of cells over time
Direct Count
cell counts done microscopically mthat measure the total number of cells (living or dead) in a population
Plate Counts
only measures viable cells
viable cell counts require one of which two culturing methods?
1) Spread Plate method

2) Pour Plate method
Minimum Temperature
below this no growth occurs as cytoplasmic membrane malfunctions
Optimal Temp
growth is most rapid
Maximum Temp
above this growth is not possible as proteins denature
What is the typical cardinal temperature range for microbes?
30-40 degrees celsius
What are the four temperature classes of microbes?
1) Psychorophiles (low temp optima (4 deg C)

2) Mesophiles (midrange temp optima (39 deg C)

3) Thermophiles (high temp optima (60 deg C)

4) Hyperthermophiles (very high temp optima (88 deg C)
Psychrotolerant microbes
can grow at 0 deg C but growth optima is between 20-40 deg C
How do psychrophiles adapt to their cold environment (four reasons)?
1) Produce enzymes that function optimally at cold temperatures

2) higher ratio of a-helix to b-sheets in enzymes

3) higher content of polar versus hydrophobic amino acids in enzymes

4) cytoplasmic membranes have a higher content of unsaturated fatty acids, allowing membrane transport to proceed unhindered
How do thermophiles adapt to their hot environment (four reasons)?
1) have key amino acid changes in enzymes and proteins that prevent denaturation

2) increased number of ionic bonds between (+) and (-) charged amino acids

3) cytoplasmic membranes have a higher content of saturated fatty acids

4) proteins have highly hydrophobic interiors which prevents unfolding
What are the three environmental factors that effect microbial growth?
1) pH

2) Osmolarity

3) Oxygen
Microbes that grow at a pH of <5
Microbes that grow at a pH of >9
Water Activity
most microbes unable to cope in environments with low aw

in environments with low aw water flows out of the cell by osmosis causing the cell to dehydrate
Halotolerant microbes
tolerate environments with a low aw but do not grow well
Extreme Halophiles
grow in extremely salty environments (15-30% NaCl)
grow in environments with high sugar concentration
grow in very dry environments
What are the three groups of aerobes?
1) Obligative Aerobe

2) Faculative Aerobe

3) Microaerophillic
What are the two types of anaerobes?
1) Aerotolerant

2) Obligate
What are the four toxic forms of oxygen?
1) Singlet (1O2)

2) Superoxide anion (O2-)

3) Hydrogen peroxide (H2O2)

4) Hydroxyl radical (OH)
What are the enzymes that destroy hydrogen peroxide?
Catalase and Peroxidase
What is the enzyme that destorys superoxide?
Superoxide dismutase