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Mystery Lab Report Sample

767 Words4 Pages

Materials and Methods Before Mystery Microbe project started class received list of unknown microorganisms that where going to be used in the lab. This list included: Staphylococcus aureus, Bacillus cereus, Mycobacterium smegmatis, Saccharomyces cerevisiae, Serratia marcescens, Proteus vulgaris, Klebsiella pneumoniae and Escherichia coli. After researching information regarding each species and microorganism identification techniques I chose to use flow charts created based on Bergey’s Manual of Determinative Bacteriology which I found on University of Idaho web site (Identification flow charts, 2011) Unknown microbe sample B-7 was assigned to me during the first lab class. After this I analyzed colonies growth pattern, shape, color and margins …show more content…

After this class cultures of unknown were refrigerated between each use. Also I prepared gram stain of the sample as instructed in exercise 10 in Lab Manual (Alderson, pp 99-105). For this procedure step 9 was modified and prepared slide was set to air dry instead of blotting the slide dry. Gram stain of B-7 microbe was analyzed under microscope and based on the observation next tests were chosen for further analysis: EMB, MacConcey, TSIA, SIM, Citrate, oxidase, …show more content…

According to these flow charts Staphylococcus aureus, Bacillus cereus, and Mycobacterium smegmatis are gram “+”, so these species were eliminated after gram staining because unknown microbe was defined as Gram “-“. Saccharomyces cerevisiae is a species of yeast which supposed to be 2-8μm wide with length of 3-25μm. Also this microorganism produce spores which stains negative during gram staining while vegetative cell should appear gram “+”.(Saccharomyces, 2016) As was mentioned in the result section unknown sample appeared to be gram”- “ rod 0.5μm wide and around 1.5 μm long. These measurements and staining results allowed me to rejected Saccharomyces cerevisiae as an option. EMB and MacConkey agars confirmed that unknown microbe is gram negative and indicated that it should be rapid lactose fermenter. According to my data Serratia marcescens and Proteus vulgaris are non-lactose fermenters so these two species were eliminated as possible unknown. Last two microorganisms Klebsiella pneumoniae and Escherichia coli react differently for Indole and Citrate. Klebsiella pneumoniae does not produce Indole and can use citrate as only carbon source. Escherichia coli cannot survive on citrate and reacts negative for this test but can react positive for Indole. Unknown microbe reacted positive for Indole and negative for citrate. Conclusion

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