Student Version_Pre Lab

PRELAB Pre-lab handout Fill out the table to predict the characteristics of the eight-bacterial species mentioned in the reading • Indicate the shape of each bacterium, as coccus, bacillus or spirallum. • Indicate the color of bacterium after the Gram stain, MSA test and blood test. • Use (+) for a positive result and (-) for a negative result in the catalase, oxidase and coagulase tests. Names of “unknown” bacteria Morphology Differential stain Isolation test Biochemical test Gram stain MSA test Blood test Catalase test Oxidase test Coagulase test Staphylococcus epidermidis Coccus Purple Pink Gamma - - - Staphylococcus aureus Coccus Purple Yellow Beta + - + Streptococcus pyogenes Coccus Purple Pink Beta - - - Streptococcus pneumoniae Coccus Purple Pink Alpha - - - Enterococcus faecalis Coccus Purple Pink Gamma - - - Bacillus subtilis Bacillus Purple No growth Gamma + - - Escherichia coli Bacillus Red No growth Gamma + - - Pseudomonas aeruginosa Bacillus Red No growth Gamma + + - Answer the two questions below: Based on the table, which test(s) (differential stain, isolation test, or biochemical test) is most helpful in distinguishing between the two Gram-negative rods? The oxidase test is the most helpful in distinguishing between the two Gram-negative rods, E. coli and P. aeruginosa. E. coli is oxidase-negative while P. aeruginosa is oxidase-positive. An“unknown”bacterium was cultured on nutrient agar. The bacterium turned purple when Gram stained. The unknown presented as individual and clustered rods when observed under the compound microscope at 1000X magnification. Each rod was ~1.0 μm broad and 2 to 4 μm long. Biochemical testing showed the bacteria was able to hydrolyze hydrogen peroxide. Based on this summary and your table, what is the unknown bacteria? it appears to be Escherichia coli..