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38 Cards in this Set

  • Front
  • Back

Bacterial growth

an increase in the number of cells

How to bacteria reproduce

asexually by binary fission

What are the two types of bacterial growth

quantitative- number of bacterial cells present

qualitative- type of bacteria present

generation time

the time it takes for a population of bacteria to double

What are the 4 phases of growth

log phase, lag phase, stationary phase, and death phase

Log phase

bacterial cells are metabolically active, but havenot started reproducing

Lag phase

cells are reproducing at exponential rate

Stationary phase

rate of cell reproduction is equal to therate of cells dying

Death phase

cells dying off at exponential rate due to lack of nutrients

What are some examples as to why you would need to quantify bacteria

Dairy manufacturers need to know the number of bacteria present after pasteurization


measures the turbidity of liquid samples

More light transmitted through liquid sample = lower cell countLess light transmitted through liquid sample = higher cell count

Membrane filtration method

A count of the visible colonies on the membrane surface gives thenumber of viable microorganisms

Cell count plate

1. Each colony was started by a single cell-colony forming unit (CFU)

2. Count the number of colonies to get an idea of how many cells were placed on the plate.

3. Multiply number of colonies by dilution factor to get the number of cells in the original sample.


providing the needed oxygen requirements for cultures


organisms require oxygen for cellular respiration, 2 types.

Obligate aerobes

need oxygen at atmospheric levels


use oxygen for respiration, but at a lowerlevel than in the atmosphere


do not use oxygen for cellular respiration, 3 types.

Obligate anaerobes

do not use oxygen for respiration andcan not grow in the presence of oxygen

Aerotolerant anaerobes

do not use oxygen for respiration,but can grow if oxygen is present

Facultative anaerobes

can grow with or without oxygen


bacteria that require an increased carbondioxide environment (3-10%)

Thioglycolate broth

used to grow anaerobes

Cultural Characteristics on Agar Plate are...

shape, margin, elevation, size, texture, appearance, pigment, optical property

Different shapes:

circular, rhizoid, irregular, filamentous, spindle

Different margins:

entire, undulate, lobate, curled, rhizoid, filamentous

Different elevations:

flat, raised, convex, pulvinate, umbonate

Cultural characteristics on agar slant:

tapered, lobed, tapered and beaded, beaded, branched, rhizoid


spherical bacteria, capable of dividing in any direction




4 that look like a box


organized but overlapping, coccus




rod shaped bacteria, divides end to end.


bacillus overlapping


wavy shape, rigid


coiled or cork screw shape, flexibl


comma shaped, slightly curved rod