Lab Exercise 44 PDF

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Lab Report 44 Name: __Michele Glantz__ Date: ___6/11/19_______

Litmus Milk Your Results and Observations Draw your results or photograph them with your mobile device and describe the result and its interpretation in the table.

E. coli

Organism

Alcaligenes faecalis

Escherichia coli

Result (appearance/color of the medium) Litmus is pink

Alcaligenes faecalis

Litmus is a light purple

Bacillus cereus

Litmus is dark purple at the top, lighter purple throughout, and a brownish/”tealike” color towards the bottom

Bacillus cereus

Interpretation Bacterium has fermented lactose, acid is produced Alkaline reaction associated with the breakdown of the protein casein Digestion is starting, the milk is starting to clear

Interpretation and Questions 1. The ability of Bacillus cereus to cause disease is associated with the ability it has to produce secreted toxins or exoenzymes. These include emetic toxin, hemolysins, enterotoxins, and

Lab Report 44 protease. Which of these toxins or exoenzymes would be involved in the growth of B. cereus in litmus milk? Bacillus cereus produces an enterotoxin & can cause food poisoning (intoxication), including one form that is often associated with fried rice held for hours at warm temperatures, associated with the growth in litmus milk.

2. As described in the previous question, B. cereus produces emetic toxin, hemolysis, enterotoxins, and proteases. Which of the media used in exercises 14-17 could be used to detect one of these toxins or exoenzymes? Why? In exercise 17, the MacConkey Agar is able to differentiate between non-lactose fermenters and lactose fermenters. It is useful in the identification of enteric bacteria, and acid is produced and released into the medium during the fermentation of lactose. Like it in the Litmus Milk test, if the organism ferments lactose, acid is produced. Both give off a color change when acid is produced, and lactose is fermented....