Enterococcus faecalis ATCC 25922-blue color with the addition of iodine (starch negative) Uses.bovis ATCC 33317-clear halo around colony with the addition of iodine (starch positive) Test the performance of the agar using the following test organisms. Perform QC on each new lot of starch agar prior to using them. Inspect starch agar for freezing, contamination, cracks, and dehydration prior to storage and before use. Heart infusion agar with 2% starch or Mueller Hinton agar (MHA) (MHA contains amylose and thus can be used to test for starch hydrolysis, avoiding purchasing additional media.).As no amylose is present in the medium surrounding the bacterial colony, clearing around the bacterial growth is seen (there is no color development). When bacteria capable of producing α-amylase and oligo-1,6-glucosidase are grown on starch agar, they secrete enzymes into the surrounding areas and hydrolyze the starch. Depending on the concentration of the iodine used, iodine turns blue, purple, or black in the presence of starch. If there is no enzyme present, and therefore no hydrolysis, the amylose, and iodine react together to form a blue color. The Petri plate is then flooded with an iodine solution. The test organisms are inoculated onto a starch plate and incubated at 30☌ until growth is seen (i.e. In starch hydrolysis test (also known as amylase test), we use starch agar, which is a differential nutritive medium. The bacterial cell to be used in metabolism. These molecules are readily transported into So only bacteria that secrete exoenzymes (α -amylase and oligo-1,6-glucosidase)Īre able to hydrolyze starch into subunits (dextrin, maltose, or glucose). (Janie Sigmon, York Technical College, Rock Hill, SC).įigure 6: Positive and Negative Gelatinase Activity Produced by Serratia marcescens and Micrococcus roseus (Labeled view) (Janie Sigmon, York Technical College, Rock Hill, SC).Starch molecules are too large to enter the bacterial cell, The gelatin in tube B is still solid which indicates no gelatinase produced by Micrococcus roseus. Note the liquification of the gelatin in tube A by Serratia marcescens which indicates the presence of the enzyme gelatinase. Both tubes were incubated at 25☌ for 24 hours followed by refrigeration for 30 minutes. Tube A was inoculated with Serratia marcescens and tube B was inoculated with Micrococcus roseus. Gelatin (BD Difco) was inoculated using the stab technique and an inoculating needle. Sturm, Cabrillo College, Aptos, CA).įigure 5: Positive and Negative Gelatinase Activity Produced by Serratia marcescens and Micrococcus roseus. Note: red color in the agar is pigment produced by Serratia marcescens. The Escherichia coli culture exhibited solidified agar after icing, indicating that gelatinase was not produced. The agar in the Pseudomonas aeruginosa and Serratia marcescens tubes remained liquid after incubation and icing, indicating digestion of gelatin by the exoenzyme gelatinase. Pseudomonas aeruginosa (top), Escherichia coli (middle), and Serratia marcescens (bottom) were inoculated into gelatin agar and incubated for 1 week. (Anne Hanson, University of Maine, Orono, ME).įigure 4: Gelatinase. Inoculated culture plates were incubated for 24 hours. Negative gelatin hydrolysis exhibited by Escherichia coli (B) is indicated by the absence of a clearing zone around the colony. Positive gelatin hydrolysis exhibited by Bacillus subtilis (A) is indicated by the clear zone around the colony after the addition of saturated ammonium sulfate. Gelatin hydrolysis test using the nutrient gelatin plate method. Torres, University of Santo Tomas, Manila, Philippines).įigure 3: Gelatin hydrolysis test. (Thomas Edison dela Cruz and Jeremy Martin O. After 30 minutes in an ice bath, the uninoculated control remained solid. Torres, University of Santo Tomas, Manila, Philippines).įigure 2: Gelatin hydrolysis test. Gelatin hydrolysis was observed after 3 days of incubation. After 30 minutes in an ice bath, the nutrient gelatin tube inoculated with Bacillus subtilis exhibited positive gelatin hydrolysis as shown by medium liquefaction. Download the PowerPoint PowerPoint Contentsįigure 1: Gelatin hydrolysis test.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |