Buffered charcoal yeast extract (BCYE) agar is a selective growth medium used to culture or grow certain types of bacteria, particularly the Gram-negative species Legionella pneumophila.
The yeast extract in BCYE is the rich source of nutrients (vitamins, nitrogen, and carbon) that the bacteria depends on for growth.
[1] BCYE may be supplemented with antibiotics to select for legionellae, especially if screening an environmental or non-potable water specimen.
Preparation of BCYE agar - copied from CDC Laboratory Guidance for Legionella :[4] The medium must be mixed frequently during the pouring to keep the charcoal particles suspended.
[4] Results to expect:[2] The Legionella bacteria that are smooth, colorless to blue or grey will become more white and filamentous over time and appear green and yellow fluorescent under UV light.