Microbio lab practical 2 Questions With Complete Solutions

TSI correct answer: Triple Sugar Iron Yellow= acid production or fermentation of the sugars in the slant or butt. Gas production= indicated by the agar lifting up or breaking Red= negative or uninoculated Black= H2S production due to FeS precipitation (think salmonella or proteus) The source of Sulfur for H2S production by bacteria is the amino acid Cysteine TSI additional correct answer: Triple Sugar-Iron agar slants. is a differential medium containing 3 sugars called glucose (also referred to as dextrose), lactose and sucrose. This medium is used to identify intestinal bacteria capable of fermenting glucose with the production of acid from other Gram-negative bacteria. Yellow slant-lactose and sucrose are fermented and acid is produced. IMViC correct answer: Indole, Methyl Red, Vogues- Proskauer ,and Citrate EMB correct answer: Eosin-Methylene Blue agar plate. Is selective for gram negative bacteria and it differentiates between lactose and non lactose fermenters. E. coli colonies are blue-black with a metallic green sheen EMB additional correct answer: Eosin Methylene Blue. Green metallic sheen colonies on EMB = E. coli because it is such a strong lactose fermenter. Pink to Purple colonies = normal lactose fermenters while white colonies = non lactose fermenters. MAC correct answer: MacConkey agar plate contains crystal violet (dye), lactose, bile salts, and a pH indicatior for differentiation of gram negative bacteria. MAC (MacConkey agar plate) is also selective for gram negative bacteria. Bile salts