Micro Lab Quiz 6

Generation Time

the time it takes for the bacteria population to double

• genetically determined

• influenced by nutritional and environmental factors

Lag phase

bacterial cells are metabolically active but have not started reproducing

• species specific

• media dependent

log phase

cells are reproducing at exponential rate

• number of cells doubles every generation time

stationary phase

rate of cell reproduction is equal to the rate of cells dying

death phase

cells dying off at exponential rate

bacterial growth

increase in number of cells

qualitative bacterial growth

what organism is growing

quantitative bacterial growth

how much bacteria is present (number of cells)

spectrophotometer

measures turbidity of a liquid sample

• the amount of light absorbed or transmitted is proportional to the number of bacterial cells in the solution sample

  • absorption: how much light is absorbed by the specimen

    • more cells=higher absorption

  • transmission: how much light passes through the sample

    • higher transmission=lower cell count

cell count plate

each colony was started by a single cell-colony forming unit (CFU)

• how many cells were placed on a plate?

  • multiply the number of colonies by dilution factor

    • get number of cells in original sample

aerotolerance

organisms ability to survive and grow in the presence of oxygen without using it for energy production

aerobic

organisms require oxygen for cellular respiration

obligate aerobes

need oxygen at atmospheric levels

microaerophiles

use oxygen for respiration but at a lower level than in the atmosphere

anaerobic

do not use oxygen for cellular respiration

obligate anaerobes

do not use oxygen for respiration and can not grow in the presence of oxygen

aerotolerant anaerobes

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

faculatative anaerobes

can grow with or without oxygen

capnophile

bacteria that require an increased carbon dioxide environment

• (3-10%)

different methods that allow for anaerobic growth

• gaspak jars

• specialized media