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Isolation and Identification of Bacteria Lab Report
Fundamentals of Microbiology (MCB 2610)
University of Connecticut
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Amanda Idusuyi Kathleen Feldmen MCB 2610 Nov. 29, 2018
ISOLATION AND IDENTIFICATION OF BACTERIA
INTRODUCTION
In this experiment, the objective was to identify two unknown microorganisms. It is important to identify bacteria because it can lead us to discover new useful bacteria as well as harmful bacteria that must be treated and contained. It will also show us the properties of each bacteria and how they are different from each other. Microbes can grow in a number of environments and may require many different nutrients to survive. The experiment required us to streak and culture two plates and use numerous techniques, such as staining and biological analyses, to correctly classify our isolates. We obtained our isolates from a mixed culture given at the start of the semester. Microbes are always all around us. Some microbes can be beneficial to the human body and others can cause harm. It is important that there is continuous research on bacteria to enhance our knowledge, thus keeping our bodies safe and healthy. If a new bacteria was found in a spring where drinking water is collected, we will need to conduct testing to find out if the bacteria is harmful, beneficial or neutral. These tests will keep us educated and informed about the life around us. The purpose of this experiment was to use a mixed culture of unknown
bacteria to create two isolates. The two isolates would then undergo a series of tests completed over the course of the semester. These tests would help identify and classify each of the isolates.
ISOLATION/ EXPERIMENTAL PLAN See page 113 in lab manual.
RESULTS Data tables submitted in class (117, 119). We used the T-streak method to streak two plates. On one plate we acquired two isolates, isolate A and isolate B. Isolate A was gram positive and had a coccus shape. The cell size was about one micrometer and was arranged in a clustered formation. It tested negative for the catalase test, therefore it was identified to be Enterococcus faecalis. Isolate B was gram negative with a rod shape. Its cell size was about two micrometers and it was arranged in a clustered formation. The microbe tested negative for oxidase, so a lactose test was completed. The lactose test showed no fermentation, therefore the bacteria was identified as Salmonella enterica.
DISCUSSION The goal of this experiment was to use a mixed culture to create two separate isolates. Different tests were completed throughout the semester to correctly identify each organism. A liquid mixed culture was supplied at each lab bench. We used the aseptic technique to sterilize our inoculating loops for bacteria extraction and streaking. We used the T-streak method on two agar plates and once incubated we would choose the plate with more colonies. After choosing the best plate, we discarded the other and looked for colonies that were distinct in form, elevation
the bacteria was cocci shaped then a catalase test must be performed. This test will show the presence of catalase by using hydrogen peroxide. A positive test will indicate the bacteria is Staphylococcus aureus. A negative test will indicate the bacteria is Enterococcus faecalis. Isolate A retained the crystal violet stain and turned purple, therefore it was gram positive. Since it was gram positive with a cocci shape and tested positive for catalase, because of bubble formation, the specimen was S. aureus. Isolate B did not retain the crystal violet stain and turned pink, therefore it was gram negative. The specimen tested negative for the oxidase test, so a lactose test needed to be completed. The specimen tested negative for the lactose test because it did not ferment the sugar. The specimen was identified to be S. enterica. My organismal results matched the known organismal results. My results were clear and did not conflict with each other. If there was a discrepancy, it could have been due to my own misinterpretation of the data or I could have made a mistake while completing the aseptic technique. Also, if I did not follow the flow chart correctly it would be very feasible to make a mistake. If I could redo the experiment, I would redo my tests from the beginning. In the beginning of lab I was very unsure of the techniques and if I was doing them correct. Now that I know how to correctly perform the tests I could do this project in a more efficient way.
CONCLUSION The section “Differentiation of Microorganisms” prepared me for this project by introducing me to microorganisms. It gave suggestions to exercises that would help to classify each specimen. This section explained the mechanisms of culture media, fermentation, enzymes, Enteropleuri tubes and motility. To identify bacteria we used culture media, fermentation and enzymes in our experiment. We cultured the bacteria on agar plates and used different tests
(catalase and oxidase) to detect for a certain enzyme. We used the Enteropleuri tubes to perform the citrate test. A real world implication that require isolation and identification of microbes is when doctors test a swab from a patients throat. They send the culture to the lab and the scientists identify the bacteria. The relay the information to the doctor in order for them to prescribe treatment. Identification of microbes can not only help us learn more about bacteria, but it can also keep us safe. We now know which bacteria can cause disease and which can aid in human health. The microflora in our gastrointestinal tract aid in digestion, without it our bodies would not be able to digest efficiently. Understanding of bacteria can help us fight infection and gain knowledge of the human body.
Isolation and Identification of Bacteria Lab Report
Course: Fundamentals of Microbiology (MCB 2610)
University: University of Connecticut
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