How to Write a Lab Report

Topics: Enterobacteriaceae, Gram staining, Escherichia coli Pages: 6 (1296 words) Published: May 6, 2011
This section introduces the reader to the study and why the study was done. This should only be a few sentences long.
Example: "There are many reasons for knowing the identity of microorganisms. The reasons range from the knowing the causative agent of a disease in a patient, so as to know how it can be treated, to knowing the correct microorganism to be used for making certain foods or antibiotics. This study was done by applying all of the methods that have been learned so far in the microbiology laboratory class for the identification of an unknown bacterium." MATERIALS AND METHODS

This is where the details of the study are listed. Where did the specimen come from, and what methods were used to identify it? Be specific, but do not re write the lab manual. One way is to mention the names of the materials used and reference the lab manual for the procedure or method and then continue to elaborate when necessary. See example 1. Example 1: "An unknown labeled as letter G was given out by the lab instructor. The methods that have been learned thus far for identifying bacteria have been applied to this unknown. Procedures were followed as stated in the course laboratory manual by De Mers (1), unless otherwise noted.

The first procedure that needed to be done was to streak the unknown out on a Trypticase Soy Agar plate, using the T streak method described in the lab manual.. This needed to be done in order to test the purity of the unknown. After the plates were incubated and grown, the morphology was observed and recorded and a Gram stain was performed. Quality control bacteria were Gram stained along with the unknown to make sure that the Gram stain reaction was done correctly . After determining the Gram reaction, specific biochemical tests were performed. The biochemical tests were chosen from the unknown identification tables that were in the lab manual. Since unknown G was determined to be a Gram negative rod, an oxidase test was performed and the organism was inoculated into a BCP lactose tube. Note all of these tests were performed by the methods listed in the lab manual by De Mers (1). Table 1 lists the test, purpose, reagents and results. All of the following tests were performed on this unknown:

1. Oxidase test
2. BCP Lactose
3. Indole
4. H2S
5. Citrate
6. Motility
7. Methyl Red
8. Urea"
Another way is to write out the methods in detail in either a paragraph form or listed. This way is not necessary for this type of paper, since this is lab report for the identification of an unknown bacterium and the methods are explained in detail in the lab manual. If there is a procedure that the instructor added or made changes to, or the student used another procedure not in the course lab manual, then it should be written out and referenced. See some of the examples of papers identifying an unknown from the web sited below.

This is where the results are summarized. The method results should be in a table format (see examples below). This is also where the flow chart showing how you arrived at the answer is stated. A short paragraph explaining how the results are presented can be included. Example: Unknown G had the following morphology on a TSA plate: medium sized opaque cream colored colony. After determining that it was a Gram negative rod, an oxidase test was performed and it was inoculated into a BCP lactose tube and onto a TSA slant. Table I lists all of the biochemical tests, their purpose and results. The results are also shown in a flow chart form. Example: Table 1: Biochemical Test Results

Gram stain To determine the Gram
reaction of the
Crystal violet,
Iodine, Alcohol,
Pink rods Gram
Oxidase test To determine the
presence of
cytochrome c
Oxidase paper Purple / black
color change
BCP Lactose To determine the
ability of a bacterium
to ferment a specific

References: Diego: Montezuma publishing, 2004
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