Unknown reports in microbiology are written in scientific format. Scientific writing is written differently from other types of writing. The results of the exercise or experiment are what are being showcased, not the writing. The purpose of scientific writing is not to entertain, but to inform. The writing should be simple and easy to understand. There is a specific style that must be followed when writing scientific reports.

Scientific writing is typically written in the passive voice. The pronouns “I”, “We” and “They” are not typically used. For example, instead of writing “I used a TSA agar plate to isolate my unknown,” it is customary to write, “A trypticase soy agar (TSA) plate was used to isolate the unknown.”

It is also customary to write in the past tense for most of the report. This includes the introduction, the summary, the description of the materials and methods and the results. The present tense is reserved for the conclusions about the results.

Some other general rules that should be followed are: Microbial nomenclature: The name of the bacterium should written and spelled correctly. The name should be italicized or underlined. Italicized is preferred. For example, Staphylococcus aureus, the genus is capitalized but the species is not. After the full genus name is given in the paper, it can be written as S. aureus, but still italicized. This is as long as there in no other genera in the paper that starts with the same letter.

Proper names such as Gram (in Gram stain) should always be capitalized. All figures and pictures need to be labelled and explicitly referred to in the report.

Font (times new roman 12) and use of margins should be consistent in the report. You should also follow the order of the parts of the report as they are laid out below.

The report should be checked for grammatical and spelling errors before submission. Your report should be thoroughly proofread before you submit it.


(Note: Other than the title page, the pages of the report must be numbered)


There should always be a title page and should include the following information:


Title should be centered and at the top or in the middle of the page


This information should be centered and at the bottom part of the title page:


DATE (the due date)




Title should be centered and at the top or in the middle of the page


This information should be centered and at the bottom part of the title page:


DATE (the due date)




This section explains why we did the experiment, its importance, and gives a brief overview of what we did. This should only be a few sentences long.


For the materials section you need to include a bulleted list of all materials used for the experiments to be completed, as well as their amounts (this does not include having specific amounts of liquids used, but instead things like numbers of slides/plates/tubes used).

The methods section is where the details of the study are listed. Where did the bacteria you are working with come from, and what methods were used to identify it? Be specific, about WHY you did each test/step. There are two ways to address the methods: 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.

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.

Appropriate discussion of controls should also be included within the methods section when discussing completion of the Gram/endospore stain and selective plating methodology. For most of the experiments that you perform in this course, you will include controls. Controls are samples whose identity you already know that are subjected to the same procedures as your unknown sample. A positive control is a known sample submitted to the procedures that will show you a positive answer. In this exercise you inoculate sectors on the control medial plates with laboratory stock bacteria because you know (initially, by looking up the organism in your text, lab manual or on-line; later, you’ll know this from the experience of working with the organism and various media) how these bacteria are supposed to behave on a particular medium.

For instance, in this exercise you inoculated mannitol salt media with Staphylococcus aureus (S. aureus) and Staphylococcus epidermidis (S. epi). These are both positive controls for the selective nature of the mannitol salt agar because they will both grow on the media. Only S. aureus, however, is a positive control for the differential nature of mannitol salt because it will ferment the mannitol, drop the pH of the surrounding media and cause a color change to occur. The media will change from pink to yellow.

A negative control is a known sample that should show you a negative result. In the example (above) of the mannitol salt media S. epi is an example of a negative control for the differential nature of the media. S. epi does not ferment the mannitol and so no media color change occurs. E. coli might be considered a negative control on the selective nature of mannitol salt media.


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 bacterium Crystal violet,

Iodine, Alcohol, Safranin Pink rods Gram

negative rods

Oxidase test To determine the

presence of cytochrome c Oxidase paper Purple / black

color change Positive

oxidase test

BCP Lactose To determine the

ability of a bacterium to ferment a specific carbohydrate None Color change

from purple to yellow Positive

lactose fermenter

Using a Dichotomous Key (Flow Chart) to ID an Unknown

A dichotomous key is a way of dividing groups of bacteria based on their physical or metabolic attributes.

“Dichotomous” means ‘dividing into two parts’. A group of bacteria are divided into two groups on the

basis of a certain characteristic (i.e. cellular morphology). This group is then subdivided into two groups on

the basis of a second feature, and so on. Such a key, based on the stain results and media, is provided at

the end of this exercise. You are directed to use the results of the differential stains (Gram stain, acid fast

stain and endospores stain) and differential and selective media (MacConkeys, EMB and Mannitol Salt) to

determine the identity of your unknown. The final product will look like a flow chart and will be included in your final lab report.

The number of unknowns in this first lab report is limited to the six types of bacterial cultures in stock in the lab. In the clinical setting the potential number of unknowns is many times this. Thus, much more than the few characteristics of these cells is needed to identify the genus and species of the bacterium; the metabolic

capabilities of the organism are studied in more detail during Lab Report 2. Below is an example of more complex flow chart, but it shows you how they should be formatted.

right29210000Example Flow Chart


This section interprets the meaning of the results. The following questions should be answered here: How did the test result lead to identification? Was it the correct identification? If not, why not. What problems were encountered (if there were none encountered in your testing you MUST indicate this in this section? This is also where the background information on the organism (environment/pathogenicity) that was identified is mentioned. You must cite all sources utilized for this background information within this section.


Note: the minimum number of references is three, the lab manual and 2 other scholarly sources. The correct citation for the information given to you about the staining procedures and plate information is below (DeMers) and should be referred to when addressing procedures. If you are utilizing any procedures outside what I have given this should be referred to and cited.

Correct reference format must be used, we use APA formatting. There are 2 types of citations: in text and works cited. In text citations are included next to the information from sources within the paper an example of an in-text citation would include the author’s name, and date of access (Author, Date of Access). You should utilize in text citations within the report to denote the use of source material, it is never acceptable to copy and paste from sources, but any use of source material MUST have an accompanying in-text citation. The second type of citation is at the end of the report and is where all sources are formally cited. The complete formatted works cited should be at the end of the paper. See example 1 under materials and methods. Spelling of the authors of the references must be correct.


De Mers, Marlene. Fundamentals of Microbiology Laboratory Manual, 4 th edition. San Diego: Montezuma publishing, 2004.

Go Here to Find Examples of APA: Report Grading Rubric:

Item Pointers What to Include Points Awarded

Title page

Follow the guide above. Title, Unknown #, Name, Date, Instructor`s Name, Course Name, Semester/Year, Section # 2 Virtual Quizzes Were both quizzes each completed within 2 tries? 3 Formatting of Report/Grammar Spelling All formatting pointers are given above. Page #s, Font, Order of Report, Consistent Margins, Passive Voice, Spelling/Grammar, Past Tense 10 Intro Why we are doing this? Why is it an important thing to do? Few sentences explaining why we did the experiment, its importance, and a brief overview of what we did 10 Materials and Methods All details. You can reference the lab manual but, you need to say what specifically the test was for. See description above.

-Make sure to list ALL supplies and their amounts (i.e. how much, how many).

-Remember you can reference the lab manual for the actual methods, BUT you must tell WHY you did the test and what it was used for etc.

-Was use of controls discussed? 15 Results You need to EXPLAIN your results and show them visually. -Summary of results

-Labelled figures & tables

-Flow chart you used to decide what bacteria you have (i.e. your process of elimination) 15 Discussion/Conclusion You need to say why you went from one test to the next (logically)… “I did this test my result was this so my next thing was this because…..” This section interprets the meaning of the results. The following questions should be answered here:

-How did the test result lead to identification? How did your result compare to controls?

-Was it the correct identification? If not, why not.

-What problems were encountered? -This is also where the background information on the organism (environment/ pathogenicity) that was identified is mentioned. 15 References In text citations done properly and end of report works cited done properly with APA format Include In Text Citations and Works Cited.

**This portion is super important. Make sure you ARE NOT COPYING FROM SOURCES OR LAB PARTNERS…you will also submit this report through TurnItIn and it will catch any copying which is plagiarism and will earn you a 0 on the lab report.** 10 Total 80