TSI test determines whether a gram-negative rod utilizes glucose, and lactose or sucrose fermentatively and forms hydrogen sulfide.
Catalase test is used to distinguish among Gram-positive cocci. Staphylococci are catalase-positive but Streptococci are catalase-negative.
Gram-positive bacteria retain the crystal violet-iodine complex and stain purple, whereas gram-negative bacteria stain pink.
Blood agar is an enriched medium which supports growth of gram-positive cocci and differentiates them on the basis of hemolysis (α, β, or γ).
Bacteria can be grown in an artificial medium in the laboratory. Growth medium can be broth, agar or biphasic. Medica can be categorized based on functions.