Read the report and answer all questions. MacConkey agar is a selective and differential medium used for the isolation of Gram negative bacilli and the differentiation of lactose fermenters and nonlactose fermenters. The selective ingredients, crystal violet and bile salts, inhibit most bacteria other than Gram negative bacilli. The differential ingredients are lactose and neutral red (pH indicator). A lactose fermenter will produce acid and its colonies will be a shade of pink to purple. A nonlactose fermenter will not produce acid, and its colonies will be colorless. Which of the following will form pink colonies on MacConkey agar? multiple choice 1 glucose fermenters lactose fermenters nonglucose fermenters nonlactose fermenters What is the role of neutral red in MacConkey agar? multiple choice 2 selective ingredient energy source pH indicator buffer What is the role of the crystal violet and bile salts in MacConkey agar? multiple choice 3 these ingredients make MacConkey selective by inhibiting Gram positive bacteria nitrogen source pH indicators carbon and energy source Which terms apply to MacConkey agar? multiple choice 4 selective and differential enrichment differential only selective only