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.
Salmonella-Shigella plates. Salmonella-Shigella (SS) plates are used to detect bacterial contamination on raw meat. Salmonella-Shigella agar plates contain lactose, bile salts, ferric citrate, and neutral red.The bile salts select for Gram-negative bacteria.oliform bacteria such as E. coli will ferment the lactose in the media, resulting in bacterial growth with a pink color. (They do not produce any hydrogen sulfide.) Members of the genus Salmonella will not ferment lactose, but do product hydrogen sulfide gas.