P.S. This is order is not a full lab report, but only a lab abstract. Please review the file carefullyTitle: A Brief Informative Title That Describes the Experiment
Hypothesis: This is a brief tentative explanation of how you think things work in this
system.
Question: What is the question that your experiment is exploring to see if your
the hypothesis is accurate or not?
Experimental Hypothesis: This should be in the form of an if/then statement that is
predictive of the answer to your question and your experiments outcome.
Rationale: Here you should explain some background information and explain why
you made the prediction found in your hypothesis
Methods: Explain what you did, how you did it during the simulation, experiment, or
lab module. This should be prose, not a list like a recipe. Include any statistics here
too.
Results: Here is where you briefly describe significant results and refer to the data and information contained in the Figures and Tables below.
Conclusions: Explain what your results mean in the context of your question and
hypothesis.
Literature Cited: Citations that you used and are cited in the above sections. This
the section cannot be empty.
Figures & Tables: Add Figures and Tables in this section. Figures and Tables must
have a descriptive caption, legends, be numbered separately and sequentially.
Title: Bacteria Population Growth Rate
Hypothesis: At 40 C the bacteria will have the greatest optimal growth rate because higher metabolic rate
as the temperature increases. (P.S. from data, our hypothesis was rejected, could be human error or else)
Question:
Experimental Hypothesis:
Rationale:
Methods:
Results:
Conclusions:
Literature Cited:
Figures & Tables:
So I use data to graph the average absorbance first,
then pick those 3 points that make linear
(log phase), then use the trendline equation to do the rate of change at last.
Temperature Rate of Change
25 0.2025
30 0.206
35 0.237
40 0.193
Comparison of Bacterial Population Growth Across Environmental Conditions
In this exercise, growth of a common bacterium Escherichia coli (E. coli) will be examined under four different environmental conditions to identify which is optimal for growth. The data will also demonstrate important aspects of population growth in a closed system.
Because this is a long experiment, it will be started before the lab period begins and run across four lab periods (hereafter referred to as an experimental run). Data will be combined and shared among lab sections within an experimental run. This is an eligible topic for a lab report. However, the report must contain data for all temperature conditions collected across all lab periods involved in your experimental run.
Learning Objectives
?Study growth of a population in a closed system
?Investigate phases of logistic population growth
?Compare the effects of environment on population growth
Materials
?Water baths set at appropriate temperature
?Spectrophotometers and cuvettes
?1000 ?l pipettors
?8 Flasks of TSB media
?E. coli stock culture
Procedure
Students will be working by bench and examining the following conditions:
?Bench 1 = E. coli grown at 30°C
?Bench 2 = E. coli grown at 35°C
?Bench 3 = E. coli grown at 40°C
?Bench 4 = E. coli grown at 45°C
1.Two flasks that contain 200 ml of tryptic soy broth (TSB) will be placed in each water bath at different temperatures.
2.One flask in each water bath will serve as the control. It is not inoculated and will be used to zero the spectrophotometer at least once per lab. The other flask will be inoculated with 5 ml of an E. coli culture that was started on the previous day.
3.The initial inoculation for a run of the experiment will occur at the beginning of the 8:30 AM lab section, one half hour before the first reading is taken. This is time T0
4.Zero the spectrophotometer using the control and take your initial reading at a wavelength of 600 nm (spectrophotometer should be blanked against the TSB control).
5.Shake the flask gently for 20 seconds before collecting a sample to mix bacteria. Using good sterile technique and a fresh pipette tip each time, sample the inoculated flask and take your spectrophotometer reading. If you are the first lab section for an
experimental run, this reading is recorded as time one (T1) in the experiment. Record the actual time this reading was made. (T0 was the time the sample was initially inoculated.
We are assuming the absorbance is that same as the control).
6.Return the flask to the water bath and allow to incubate for 1 hour. Collect sample and read absorbance again. This is time T2. Collect a sample again after 1 hour for the T3 reading. Record the actual time the reading was made for each sample. For example, if a flask was inoculated at 8:30 am, T1 = 9:00, T2 = 10:00, T3 = 11:00, T4 = 2:00, etc.
7.After taking your sample, return the flask to the water bath. You will ultimately take three readings from your flask.
8.In the following lab sections, readings will be made at T4-T6, and T7-T9 as described by the TA. Record the actual time the reading was made for each sample.
9.Data will be collected from four lab sections over the course of approximately 12. After the last lab section has collected their data, they will be shared with all sections within that experimental run for analysis.
10.When all data have been collected and shared, prepare a graph of the results (x-axis: time, y-axis: absorbance) and bring to class next week.
Think about the following questions after you plot your data and answer them in your notebook:
1.What does the graph show? Do you observe distinct phases?
2.Are the growth curves the same across temperatures? What is similar, what is different?
3.When was population growth (i.e., change in population size) slowest? When was it fastest?
4.What was the effect of temperature on E. coli population growth?
5.What can you conclude about population growth of E. coli? How might these results be of importance in an applied context such as food or medical services?
