Question

what do you think the colony shape and colony edge/ margin are? and also the TSI slant is yellow and butt is red, is it mean that the TSI is positive to acid?

Answer 1

1. the colony shape is irregular and the colony margin or edge is undulate. the colony is buff coloured.

2. in triple sugar iron (TSI) test, three sugars are present lactose, sucrose and glucose. bacteria that ferment any of the three sugars will produce acidic byproducts. these byproducts react with the red pH sensitive dye phenol red to yellow colour. in the above test tube, the yellow colour is present in the slant which indicates that a little glucose is fermented but not lactose within early hours of fermentation. the butt is still red where reaction didnt occur still. the slant is positive to acid as it is in yellow colour