4-5: Eosin Methylene Blue

gram- growth (inhibits gram+ growth)

what does EMB select for

strength of lactose fermentation

what does EMB differentiate for

- aggressive lactose fermentation: dark purple/black/metallic green colony growth

- weak lactose fermentation: pink to dark purple, or the color of the plate

- non fermentation: no color change

describe the different levels of lactose fermentation that can occur

metallic green (strong lactose fermentation)

what will E. coli look like on EMB

pink (weak lactose fermentation)

what will Enterobacter aerogenes look like on EMB

1. Enterobacter aerogenes because pink colonies (weak lactose fermentation)

2. Staphylococcus epidermidis because no growth (gram+)

3. Proteus stuartii because pink colonies (weak lactose fermentation)

4. Escherichia coli because metallic green colonies (strong lactose fermentation)

state which microbe is in each section based on the reaction