Experiment 11: Effect of Temperature on Microbial Growth

when do biochemical reactions occur most efficiently?

at each organism’s optimum temperature range

they can grow at a range of temps but this specific range is where they grow the fastest (maximum speed = optimal temp)

based on temp requirements, what are the 3 main categories?

1. psychrophiles

2. mesophiles

3. thermophiles

what are psychrophiles?

-5deg to 20deg

found in supercooled waters of arctic and antartica

what are mesophiles?

grow optimally at 20-50 deg

most bact meosphiles are these

what are thermophiles?

grow best at 50-90 deg

in soils where midday temp is 50deg or in compost where fermentation causes temps to increase.

when temps are above the max

enzymes denature and lose activity

when enzymes are below the minnmum

activity slows a lot

temp can also impact..?

cell memberane and transport when outside the optimal range and can also cause cell death

exp 11 learning objectives

1. how does temp promote or inhibit growth

2. growth at diff temps and identify optimal temp

3. classify them based on the 3 catergories

exp 11 materials (in pairs)

1. S. aureus lvl 2

2. Serratia marcescens

3. Geobacillus stearothermophilus

4. Saccromyses cerevisiae

5. TSA plates

6. sterile swabs

exp 11 methods

1. divide into 4, label w microbe, swag each microbe on each plate

2. label as: 4, 20-25, 37, 55

3. incubate for 48-72 hours

4. 4deg=fridge, 20-25=room, 37 and 55=incubator

Results - Staphylococcus aureus

4° = (-)

20-25° = (++) yellow-green

37° = (+++)

55 ° = (-)

optimal = 37°

Results - Serratia marcescens

4° = (-+)

20-25° = (++) red

37° = (++)

55 ° = (-)

optimal = 4-37°

Results - Geobacillus stearothermophilus (true thermophile)

4° = (-)

20-25° = (-)

37° = (+)

55 ° = (+++)

optimal = 55°

Results - Saccromyces cerevisiae (yeast + fungi)

4° = (-)

20-25° = (+++) yellow-green

37° = (+++)

55° = (-)

optimal = 20-37°

what is the optimum growth temp for most human pathogens?

37°

normal body temperature bc mesophiles, so wtv the host temp is, pathogens are adapted to survive in that temp