Alkaline slant - Observation for Carbohydrate Utilization Pattern Test

Alkaline slant (red) and acid butt (yellow) with or without gas production - This indicates fermentation of glucose only. As glucose concentration is low, only small amount of acid is produced which gets oxidized rapidly on a slant surface. The peptones in the medium are also used in the production of alkali so slant is red. The acid reaction is maintained in the butt due to slow growth of organism and low oxygen tension so it becomes yellow.