Bacteria in Produce—Laboratory Report Guide
Read the general guide on how to write a lab report. Follow the instructions for
the various parts of your write up. Your report must include the following sections
for full credit. For the results, you must include tables and a figures as described
in the Results section.
Title
Provide a specific descriptive but concise title
Introduction
Your introduction should have three paragraphs:
(1) Define the topic of microbes in produce
(2) Specific examples based on scientific studies
(3) Objectives of the experiment.
You must describe at least two specific examples related to microbes in food.
This could be published journal articles that describe something about microbial
ecology of food; specific pathogens or other known prokaryotic life;
epidemiological data about food borne illnesses; toxins associated with foodborne pathogens; etc. You must include your source of information and it has to
be a published scientific paper (i.e. journal article of some kind).
Note #1: paragraphs have structure:
(1) Start with a topic sentence.
(2) The middle section should support the topic sentence.
(3) The final sentence should relate back to the topic sentence.
Note #2: Topic sentences should also be used to link paragraphs together using
transitioning statements or phrases.
Methods
Organize into sub sections based on what was done. Use subheadings to help
organize this section:
Growth Media
Sample processing
Bacterial Enumeration
Data Analysis
Results:
Tables and Figures:
Include the following data on separate pages at the end or your report:
Table 1. make a table that summarizes the TSB and MacConkey results of
unwashed vs. washed CFU/g of each food item analyzed for both sections 223
and 229.
Table 2. Make a table that describes the abundance of Gram positive, Gram
negative, and Lac+ bacteria for each food sample.
Figure 1. A vertical bar graph that shows the affects of washing on CFU/g for
each food item. You can leave out the food items that had no detectable CFU/g.
You should also have separate bars for the TSB agar and MacConkey agar. You
could also have a two-panel figure with an A and B sub-figure. A, for TSB agar
and B, for MacConkey agar.
Figure 2. Similar to Figure 1, make a graph comparing the presence of Lac+
CFU/g on unwashed vs. washed produce.
Notes: each figure and/or table should have a concise and descriptive figure
caption. Use a log scale on y-axis if you are reporting CFU/g.
Written section
Your Results section should describe each table and figure in paragraph form.
Address the following points:
1. Bacterial abundance in unwashed produce
a. What are the trends in the CFU/g data for unwashed fruits and
vegetables?
b. Which food item has the most/least CFU/g?
c. What did the colonies look like?
d. Were there differences in CFU/g for the TSB vs. MacConkey agar for
particular samples?
2. Relative abundance of Gram positive vs. Gram negative bacteria for each
sample.
a. What samples had the greatest/least abundance of Gram +
b. What samples had the greatest/least Gram negative bacteria?
c. Are there any trends for a particular food type?
3. Relative abundance of Lac+ vs. non-lactose fermenting bacteria?
a. Sample questions as above. Describe the samples with the least/most
Lac+ bacteria.
4. The effects of washing on bacterial abundance in produce
a. What were the effects of washing on CFU/g for each sample? Did the
colonies look different than in the unwashed sample? Were there
differences in CFU/g for the TSB vs. MacConkey agar for particular
samples?
Discussion
Follow the general laboratory guidelines. In addition, address these points in your
discussion:
1. How does your CFU/g, Lac+, and Gram +/- data compare to similar studies
done by other scientists?
2. Discuss the effectiveness of washing on reducing CFU/g. Your discussion
should reference other scientific studies?
3. Describe associations of certain bacteria with specific produce items. You
could also discuss illnesses related with certain food-borne pathogens, or
studies that are more ecological. However you focus your discussion, you
must provide at least two examples. Use scientific papers to support your
discussion.
4. In your conclusion describe what could be done next.
References
Cite your sources according to the general guidelines. Use the following format:
Authors (Last name, first). Year. Title of article. Journal Name. Vol. Page number
range.
Here is an example:
Murphy, J. N., and C. W. Saltikov. 2009. The ArsR repressor mediates
arsenite-dependent regulation of arsenate respiration and detoxification operons
of Shewanella sp. strain ANA-3. Journal of Bacteriology 191:6722–6731.
For in text citations:
Shewanella sp. ANA-3 uses an ArsR-type repressor for regulating anaerobic
growth on arsenate (Murphy and Saltikov, 2009).