CLED agar (Cysteine Lactose Electrolyte Deficient medium) is a valuable non-inhibitory growth medium used in the isolation and differentiation of urinary organisms. Being electrolyte deficient, it prevents the swarming of Proteus species. Lactose fermenters produce yellow colonies on CLED agar; non-lactose fermenters appear blue. It has a pH of approximately 7.3. CLED agar contains: Cysteine is a naturally occurring hydrophobic amino acid which has a thiol group and is found in most proteins, though only in small quantities. ... Lactose is a disaccharide that makes up around 2-8% of the solids in milk. ... An electrolyte is a substance that dissociates into free ions when dissolved (or molten), to produce an electrically conductive medium. ... A growth medium is an object in which microorganisms or cells in experience growth. ... Look up urine in Wiktionary, the free dictionary. ... In biology, Proteus is a genus of Gram-negative Proteobacteria, which includes pathogens responsible for many human urinary tract infections. ... In biology, a colony (from Latin colonia) means several individual organisms of the same species living closely together, usually for mutual benefit, such as stronger defences, the ability to attack bigger prey etc. ... The title of this article should be pH. The initial letter is capitalized due to technical restrictions. ...