Dear Thao,

Regarding your question if you see the medium composition, it contains sucrose as carbon source and bromothymol blue and thymol blue pH indicators, Vibrio which utilizes sucrose as carbon source and produce yellow colonies and non sucrose utilizing produce blue green colonies on TCBS agar.

Dear Pankaj, 

I cultured and found they both yellow colonies. Thank you so much.

Best regards,

Thao

Dear Thao,

There is a great variability of metabolic phenotypes in Vibrio species, it is then possible that a same species gives different colours.

Best Regards

Léa

Thanks Léa,

Your input is a great help. I found Vibrio splendidus yielded both green and yellow in TCBS.

Best regards,

Thao

Dear Thao:

I recommend you to sterilize by filtration (0.2 um) the sucrose and also to use sucrose grade HPLC 99 % of purity or higher to be sure you don't put any inverted sucrose in the TCBS medium. I think that minimal levels of Glucose and/or Fructose could give you yellow colonies, but not due to the breakdown of sucrose by the microorganism.

Best regards, Fraga.

Dear Reinaldo,

Thank you so much for your instruction. It's interesting to know. I will give it a try. 

Best regards,

Thao

The acidification of the medium resulting from the fermentation of sucrose by Vibrio makes bromthymol blue turn yellow. Bromthymol Blue and Thymol Blue are pH indicators. ... An increased pH is used to enhance growth of Vibriocholerae, because this organism is sensitive to acid environments.