Growth as a function of temperature

To really understand an organism, we need to know about its preferences -- at what temperature does it grow best, at what temperature does it fail to grow? 

These properties constrain the types of ecological niches that an organism can inhabit.   

Organisms can be classified based on the relationship between growth rate and temperature: they range from psychrophiles to hyperthermophiles. 

PLEASE READ THROUGH THESE INSTRUCTIONS FIRST

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To insulate you from some of the realities of science, we have reduced the tedium of the measurement process somewhat in this section!

STEP 1. Launch the vSpec.  You now choose the growth temperature using the arrow cursor; once you select a temperature, press the proceed button.

STEP 2. Select the duration of your measurements.
Choose either 8, 24 or 72 hours, then press the proceed button.  Your vTA will come into the lab and take 20 evenly spaced readings during the period you choose.  Both reading times values will be displayed on your datapad.

STEP 3: Pick a duration that gives you as many A values greater than 0 and less than 1 - this will produce the most accurate estimate of doubling time.

The curve fit, from which the doubling rate is calculated, will then be plotted automatically using the region you selected.

If you select a temperature that is too high or too low, there will be no growth no matter how long you wait. If there is no growth at 72 hours, select "no growth".

Before you leave the applet, print your data graph and include it in your report.

WRITE UP

In your write up, answer the following questions.

1. What is the maximum growth temperature for E. coli under these conditions (+ or - 1°C)? 
2. What is its optimal growth temperature under these conditions (+ or - 1°C)

• Since E. coli normally grows in your gut, speculate on why its optimal growth temperature is different from the commonly cited temperature of a normal healthy human - 37°C.
• Given what is known about humans, why is it unlikely that a thermophile or a psychrophile would be a human pathogen? 
• How does lowering the temperature 15°C from the optimal growth temperature affect growth rate?
• What type of organism is E. coli (in terms of temperature preference)?  Why is your characterization of E. coli tentative?  What kinds of data would lead you to modify your characterization?