In a yeast assimilation test, what indicates a positive result?

In a yeast assimilation test, what indicates a positive result?

• A. Gas production
• B. Pigment change
• C. Growth or turbidity
• D. Colony color change

Answer: (C)

The key idea is that a yeast assimilation test measures whether the organism can use a given sugar as its sole carbon source, which shows up as growth in the medium. A positive result is indicated by visible growth, usually seen as turbidity in a liquid medium or a larger colony, because the yeast can assimilate the sugar and multiply. Gas production would reflect fermentation rather than assimilation, so it isn’t the right signal here. Likewise, pigment or colony color changes aren’t reliable indicators of carbohydrate assimilation in this test; they point to other metabolic or indicator reactions. So, growth or turbidity best signals that the yeast is able to utilize the carbohydrate, producing a positive result.

The key idea is that a yeast assimilation test measures whether the organism can use a given sugar as its sole carbon source, which shows up as growth in the medium. A positive result is indicated by visible growth, usually seen as turbidity in a liquid medium or a larger colony, because the yeast can assimilate the sugar and multiply. Gas production would reflect fermentation rather than assimilation, so it isn’t the right signal here. Likewise, pigment or colony color changes aren’t reliable indicators of carbohydrate assimilation in this test; they point to other metabolic or indicator reactions. So, growth or turbidity best signals that the yeast is able to utilize the carbohydrate, producing a positive result.