EXERCISE 13 GELATIN HYDROLYSIS

what is gelatin

an animal protein derived from collagen

what is gelatinase

an exoenzyme that hydrolyzes gelatin

what happens when gelatin is hydrolyzed

the protein molecules are broken down into amino acids and the gel is liquified

why is agar a better choice for solid culture media

mainly indigestible so remains solid

what are the materials needed for gelatin hydrolysis

slants of Serratia marcescens and Escherichia coli

sterile nutrient gelatin deeps

describe process of gelatin hydrolysis

roll needle on slant of bacteria → stab needle into gelatin deep almost to the bottom

where should you incubate the S. marcescens deep

25 degrees celsius

where should u incubate E. coli

37 degrees celcius

what does a positive result look like for gelatin hydrolysis

tube contains liquid, even after icing

LIQUIFICATION OCCURS

how long should you wait to check results

48 hours

what is urea

common nitrogenous waste product that is toxic to most cells

what can urea be broken down into

ammonia and carbon dioxide

what breaks down urea

urease

what is the clinical value of testing for urease production

for patients w diarrhea, microbiologists can isolate pure cultures of bacteria from poop, do a gram stain and test for urease

describe the process of urea hydrolysis

inoculate urea broth with bacterium → incubate at 37 degrees celsius

what does urea hydrolysis test for

production of urease

what do positive and negative tests look like for urea hydolysis

positive: red or cerise color

negative: yellow or orange red color

what is used as a pH indicator

phenol red, looking for a pH higher than 8.1 for a red color, meaning urease is produced