By Prof Jeremiah Seni Introduction The Catalase test is used to differentiate staphylococci (catalase-positive) from streptococci (catalase-negative). The enzyme catalase, is produced by bacteria that respire using oxygen and protects them from the toxic by-product of oxygen metabolism. Catalase-positive bacteria include strict aerobes as well as facultative anaerobes, although they all have ability to respire … Read more
By Prof Jeremiah Seni What Is MacConkey Agar? MacConkey agar (MAC) was developed as the first solid differential media in the 20th century by a bacteriologist, Alfred Theodore MacConkey. While working for the Royal Commission on Sewage Disposal, His role was to inspect drinking water sources for the presence of Gram-negative enteric organisms. Which usually inhabit … Read more
By Prof Jeremiah Seni Objective To detect the ability of organisms to produce citrase enzyme.The citrate test detects the ability of an organism to use citrate as the sole source of carbon and energy. Principle Bacteria are inoculated on a medium containing sodium citrate and a pH indicator such as bromothymol blue. The medium also contains inorganic ammonium salts, which are utilized as sole … Read more
By Prof Daniel Asrat Introduction The objective of Hydrogen Sulphide Test is to determine whether the microbe reduces sulfur-containing compounds to sulfides to produce hydrogen sulfide gas.Some bacteria have the ability to reduce sulphur to hydrogen sulphide. It is a colorless gas, which reacts with iron (ferrous salts) to produce black precipitates of ferrous sulphide.It also reacts with lead … Read more
By Prof Daniel Asrat Introduction The Triple Sugar Iron (TSI) test is a microbiological test roughly named for its ability to test a microorganism’s ability to ferment sugars and to produce hydrogen sulfide.[1] It is often used to differentiate enteric bacteria including Salmonella and Shigella. The TSI slant is a test tube that contains agar, a pH-sensitive dye (phenol red), 1% lactose, 1% sucrose, 0.1% glucose, and sodium thiosulfate and ferrous sulfate or ferrous ammonium sulfate. All … Read more
By Prof Daniel Asrat Principle Some bacteria have the ability to deaminate the amino acid phenylalanine, as they can produce the enzyme ‘phenylalanine deaminase’.This enzyme deaminates phenylalanine by removing its amino group, thereby producing phenylpyruvic acid (a keto acid) and ammonia (NH3). Phenylpyruvic acid forms green colour with ferric chloride solution. In the phenylalanine deaminase … Read more
By Prof Moses Joloba Principle Some bacteria have the ability to hydrolyse (breakdown in presence of water) urea to NH3 and CO2, as they can produce the enzyme ‘urease’. NH3 is alkaline (basic), due to which, it increases the pH changing the color of phenol red from yellow to pink. In the urease test, the test bacteria … Read more
By Prof Moses Joloba Introduction The indole test is a biochemical test performed on bacterial species to determine the ability of the organism to convert tryptophan into indole. This division is performed by a chain of a number of different intracellular enzymes, a system generally referred to as “tryptophanase.” Indole is generated by reductive deamination from tryptophan via the intermediate molecule indolepyruvic acid. Tryptophanase catalyzes the deamination … Read more
By Prof Moses Joloba Principle Some bacteria have the ability to utilize glucose and convert it to a stable acid like lactic acid, acetic acid or formic acid as the end product.These bacteria initially metabolise glucose to pyruvic acid, which is further metabolized through the ‘mixed acid pathway to produce the stable acid. The type … Read more