There is only a short time of the year when you can see the sun coming down into the canyon, and then only at midday. Tours at that time of the day and that time of the year sell out far in advance. You may need to book at least six months ahead of time, for a summer month tour, to take advantage of this.
The crystal violet and bile salts inhibit the growth of gram-positive organisms which allows for the selection and isolation of gram-negative bacteria. Enteric bacteria that have the ability to ferment lactose can be detected using the carbohydrate lactose, and the pH indicator neutral red.
One plate of WL Nutrient Agar and two plates of WL. Differential Agar are prepared (3). The WL Nutrient Agar plate is incubated aerobically to give a total yeast count while one. WL Differential Agar plate gives the count of acetic acid bacteria, Flavobacterium , Proteus and thermophilic bacterial. count when incubated aerobically.