Question

0 9 - - - After flood both plates with lodine, they turned purple. There is a clear zone surrounding the growth of Bacillus on Starch Agar plate but not on the Starch + Glucose Agar Plate. Starch Agar Plate Starch + Glucose Agar Plate Review Questions: 1. Which bacterium hydrolyze starch? A. Bacillus B. E. coli C. both D. neither one __2. Amylase is produced when_ A. Glu (+) Starch (+) B. Glu (+) Starch (-) C. Glu (-) Starch (+) D. Glu (-) Starch (-) 3. Starch is a polysaccharide made of_ glucose subunits. 4. Name an enzyme hydrolyzes starch: amylase Explain why you flooded plates with lodine. To produce a clear zone that indicates hydrolyzed starch 5. 6. Explain why Bacillus produce a clear zone on Starch agar plate but not on Starch+Glucose agar plate? Clear zone indicates that the organism has hydrolyzed starch.

number 2 and 6

Answer 1

2. Amylase is produced when Glu(-) Starch (+). The answer is C because the amylase zone can be seen only after the hydrolysis of starch by the enzyme.

6. Bacillus species are known to produce amylase enzyme in the presence of starch. But, in case of the presence of glucose the organism does not produce the enzyme as glucose is a monomer and is easily digested or consumed by the organism. The amylase enzyme will only be produced only when the glucose is over from the substrate and the organism is starved and it signals the production of amylase enzyme to hydrolyze the starch in the medium/substrate. This type of mechanism is called "catabolite repression".