Lab Exam 2 Review

Spectrophotometer

Measures turbidity of liquid sample using a monochromatic beam of light. Beam uses single wavelength.

Transmittance / Absorbance

The fraction of incident light that passes through a sample.

The relationship between absorbance and concentration is:

Direct/Linear

Components - Closed System Growth:

• No nutrients added, no waste removed

• 4 phases

Phases of Closed-System Growth

• Lag

• Log

• Stationary

• Death

Lag Phase

Adjustment Period

• no cell division

• high metabolic activity

Log Phase

“exponential growth”

• Exponential because the bacteria enter their maximum growth rate

• Used to determine generation time for bacterium

Stationary Phase

Stable, straight-line

• Growth rate = death rate

• nutrients become limited

• waste products begin to accumulate

= unfavorable environment

Death Phase

May happen gradually or rapidly

Some bacteria may not lyse

• All nutrients are depleted

• waste products reach toxic levels

What if dead bacterial cells do not lyse?

If the cells do not lyse, then the turbidity will not be changed enough to tell. A viable cell count must be performed.

What can bacterial growth curves tell us?

• Length of time a bacterium is in each growth phase

• optimal growth conditions

• average generation time

Cardinal Temperature:

The combination of the minimum, optimum, and maximum temperature a bacterium can grow in.

Psychrophiles:

Grows in temperatures <20 C

• Range of -5 → 20 C

• NOT HUMAN PATHOGENS

• Found in marine water, icefields, and oceans. And Alpine soils.

Norman Human Body Temp:

37C (98.6F)

Psychotrophs

Range of 0 → 30 C

CAN BE HUMAN PATHOGENS

• Found in soil, surface water, and foods.

Mesophiles

Range of 15 → 40 C

Optimal: Human Body Temp [37 C]

CAN BE PATHOGENIC TO HUMANS

Thermophiles

Range of 40 → 75 C

• Can be found in hot springs

Hyperthermophiles

Range of 65 → 110 C

• Can be found on the ocean floor’s thermal vents or ridges.

pH Definition:

The concentration of hydrogen ions in a solution

• measured on logarithmic scale from 0-14.

lower pH, high H+ concentration

ACIDIC

higher pH, lower H+ concentration

ALKALINE

pH of 7

neutral

Acidophiles

Range pH of LESS THAN 4.5-5.5

• Acidic environments

Neutrophiles

Range pH of 5.5 → 8

MOST HUMAN PATHOGENS (because most human bodily fluid is neutral pH)

Alkaliphiles

Range pH of MORE THAN 8-8.5

• Grow well in alkaline environments

Turgor Pressure

The pressure inside a cell required for survival.

Inadequate turgor pressure results in:

• Lysis (RUPTURE)

or

• Plasmolysis (SHRINKAGE)

Osmosis:

movement of water from low solute to high solute.

Goal: equilibrium

Osmotic Pressure

the force by which water moves from low to high solute concentrations.

Hypotonic

High solute inside, low solute outside

• LOW osmotic pressure

• Water moves INTO cell = LYSIS

Isotonic

Equal rates of salt and water concentrations

• everything is great

Hypertonic

Low solute inside, high outside.

• HIGH osmotic pressure

• Water moves OUT of cell = Plasmolysis

Halophiles

Bacteria that can grow in conditions of less than 3%.

Extreme Halophiles

• Type of Halophile

• Range MUST BE between 15 → 25% salinity.

Halotolerant

Wide range, low and high salinity.

Obligate Aerobes

Need oxygen.

Facultative Anaerobes

can survive with or without oxygen, will uses oxygen if present, switch to fermentation if not.

Aerotolerant Anaerobes

IGNORES OXYGEN

Oxygen isn’t used either way, can survive with or without oxygen.

Obligate Anaerobes

no oxygen allowed.

Microaerophiles

Must have VERY LOW levels of oxygen.

Capnophiles

Must have VERY HIGH levels of carbon dioxide.