Summary: Systematic Identification Of Bacillus Subtilis
Systematic Identification of Bacillus subtilis and Serratia marcescens Through a Battery of Tests and Plates
Introduction:
The purpose of this experiment was to use a systematic battery of tube tests and plates designed to lead to identification of two unknown bacterial species, from the combination of all results. A sample of bacteria was used, labeled “Sample 4”, from which both species was to be obtained, one gram positive and one gram negative. Table 1 is a list of the possible bacteria to be identified; the basic ideas and practice of identification of an unknown sample of bacteria are important for a microbiologist to develop. Not only is proper procedural practice necessary, the investigator must use critical thinking to solve the …show more content…
The bile esculin hydrolysis test is a selective and differential slant used to identify bacteria of the genus Enterococcus. The test contains bile salts to select for the desired bacteria, and differentiates because the hydrolysis of esculin and subsequent combination of the products with iron produces a black color. A positive test for the bile esculin slant is a completely blackened tube (Lindell et al, 1975). A triple sugar iron (TSI) slant is used to identify sugar fermentation in a microorganism; it contains a red pH-sensitive dye that will turn yellow under acidic conditions, such as contact with the acidic byproducts of sugar fermentation. The three sugars, sucrose, lactose and glucose, are present in specific concentrations, 1%, 1%, and .1% respectively (Hajna, 1945). The combination of the color change results and the location in the tube of the changes allows for a multitude of varying results. The TSI slant is a useful launch point for an investigation of this type, because the varying results can give a solid idea of what direction the remainder of the tests must take. A citrate utilization test is used to determine if an organism uses citrate as its only source of carbon, a positive result will change the dye in the slant from green to blue due to the byproducts changing the pH in the tube (Kiska …show more content…
A TSI slant was first stabbed through to the bottom, and then streaked along the surface with a loop. The surface of a citrate slant was streaked in a zigzag pattern. A tube of broth containing tryptophan was inoculated with a loop full of bacteria for the indole test. After incubation, two drops of Kovac’s reagent was added to this tube and the color of the drops was recorded. All of the tests above were incubated for 24 hours, with the exception of the citrate test which incubated for 48 hours at 37° C, the results were subsequently
Introduction:
The purpose of this experiment was to use a systematic battery of tube tests and plates designed to lead to identification of two unknown bacterial species, from the combination of all results. A sample of bacteria was used, labeled “Sample 4”, from which both species was to be obtained, one gram positive and one gram negative. Table 1 is a list of the possible bacteria to be identified; the basic ideas and practice of identification of an unknown sample of bacteria are important for a microbiologist to develop. Not only is proper procedural practice necessary, the investigator must use critical thinking to solve the …show more content…
The bile esculin hydrolysis test is a selective and differential slant used to identify bacteria of the genus Enterococcus. The test contains bile salts to select for the desired bacteria, and differentiates because the hydrolysis of esculin and subsequent combination of the products with iron produces a black color. A positive test for the bile esculin slant is a completely blackened tube (Lindell et al, 1975). A triple sugar iron (TSI) slant is used to identify sugar fermentation in a microorganism; it contains a red pH-sensitive dye that will turn yellow under acidic conditions, such as contact with the acidic byproducts of sugar fermentation. The three sugars, sucrose, lactose and glucose, are present in specific concentrations, 1%, 1%, and .1% respectively (Hajna, 1945). The combination of the color change results and the location in the tube of the changes allows for a multitude of varying results. The TSI slant is a useful launch point for an investigation of this type, because the varying results can give a solid idea of what direction the remainder of the tests must take. A citrate utilization test is used to determine if an organism uses citrate as its only source of carbon, a positive result will change the dye in the slant from green to blue due to the byproducts changing the pH in the tube (Kiska …show more content…
A TSI slant was first stabbed through to the bottom, and then streaked along the surface with a loop. The surface of a citrate slant was streaked in a zigzag pattern. A tube of broth containing tryptophan was inoculated with a loop full of bacteria for the indole test. After incubation, two drops of Kovac’s reagent was added to this tube and the color of the drops was recorded. All of the tests above were incubated for 24 hours, with the exception of the citrate test which incubated for 48 hours at 37° C, the results were subsequently