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Identifying Bacteria based on Enzymes and multiple test media. Lab # 9 Medgar Evers College Prof. Victor Santos. Aim. To identify bacteria based on the enzymes they have that allow them to carry out certain specific reactions! You will detect the presence of
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Identifying Bacteria based on Enzymes and multiple test media Lab # 9 Medgar Evers College Prof. Victor Santos
Aim • To identify bacteria based on the enzymes they have that allow them to carry out certain specific reactions! • You will detect the presence of • Amylase, proteases, lipases, tryptophanase, urease, and phenylalanine deaminase.
Multiple testing media • These media are important because they save us time and money by allowing us to test for several parameters at once. • Examples; Kliger’s Iron Agar, SIM, and Litmus Milk
Kliger’s Iron Agar • The Kliger’s medium contains 1.0 % lactose, 0.1 % glucose and the amino acid cysteine, peptones, ferrous salts and the pH indicator phenol red. • This medium allows you to detect glucose fermentation, lactose fermentation and hydrogen sulfide production. • Inoculate by streaking and stabbing one tube with your unknown and one with P. vulgaris, the control.
SIM • This medium is 0.7% agar so its considered semi-solid to allow motile organisms to be detected. • This medium allows you to detect motility, hydrogen sulfide production from the breakdown of cysteine, and detect the breakdown of tryptophan. • Inoculate one tube with unknown, and three controls; one with S. aureus, and one with P. vulgaris and the last one with E. coli. • YOU MUST STAB THESE!
Litmus milk • Allows you to detect several properties! A) Fermentation of sugar will lead to a pink color change due to acid formation. B) The breakdown of proteins leads to ammonia formation which raises the pH and leads to a blue color change. C) Litmus reduction leads to a white color change. This happens due to a drop in oxygen and the dye is then used as an electron acceptor becoming reduced and changing the medium to a white color. D) Coagulation of proteins can lead to curd formation. E) Peptonization or the medium becomes translucent or sometimes brown due to the breakdown of milk proteins. F) Ropiness or the formation of thick slime due to the accumulation of waste products and cells.
