Bial's (Orcinol) Test: Principle, Procedure, Result, and Uses
Bial's test (the orcinol test) detects pentose sugars, giving a blue-green color while hexoses turn muddy brown. Learn the principle, reagent, procedure, how to read the result, an...
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Carbohydrate Utilization
Various biochemical tests which are related to Carbohydrate fermentation or Utilization
Lysine Iron Agar (LIA): Principle, Composition, Results, and Interpretation
LIA differentiates enteric bacteria by lysine decarboxylation, lysine deamination, and H₂S production. Learn how to read LIA results alongside TSI and KIA to identify Salmonella, S...
Benedict’s Test: Principle, Procedure, Uses, and Limitation
Benedict's test detects reducing sugars by a blue-to-brick-red color change. Learn how to read each color, why green does not mean "safe," which sugars react, and the false negativ...
RCUT for Neisseria: The Maltose Result That Separates Gonorrhoeae from Meningitidis
Neisseria gonorrhoeae and N. meningitidis look identical under the microscope, but one uses glucose only and the other uses glucose and maltose. RCUT reads that sugar panel in 4 ho...
Kligler’s Iron Agar (KIA): Principle, Procedure, Results
A faint black line at the slant-butt junction is easy to overlook, and it is exactly the reaction that can point toward Salmonella Typhi. Full KIA principle, tube-reading rules, an...
Carbohydrate Fermentation Test: Reading Acid, Gas, and the Sugar Panel That Fingerprints a Species
Feed an organism a single sugar and watch two things: does the broth turn yellow (acid), and does a bubble collect in the Durham tube (gas)? Run a panel of sugars and the pattern o...
API 20E Test: Procedure, Reading the 21 Reactions, and the 7-Digit Profile Code
How to set up, incubate, and read the API 20E strip: which wells need oil, which need reagents, how to run the 21st test (oxidase), and how to build the 7-digit profile number for...
Voges-Proskauer (VP) Test: Principle, Procedure, Results & VP-Positive Organisms
VP test principle, the α-naphthol-then-KOH procedure, and how to tell a true positive from the copper-color false positive that trips up most students.
Methyl Red (MR) Test: Principle, Procedure, Results & MR-Positive Organisms
MR test principle, procedure, and the mixed-acid vs. butanediol fermentation logic that tells you which organisms will turn red — without memorizing two separate lists.
Triple Sugar Iron (TSI) Agar: Principle, Results, and Interpretation
TSI agar: principle, composition, procedure, and complete interpretation guide: all possible slant/butt combinations with organisms, H₂S production, gas formation, and comparison w...
Biochemical Tests Used to Identify Bacteria in the Microbiology Laboratory
A complete guide to biochemical tests used in bacterial identification, featuring over 40 tests organized by category with principles, positive results, and organisms identified. I...