Escherichia coli

Basic description of microbe:

• Straight rods

• Motile

• Facultatively anaerobic

• 1.1-1.5 μm x 2.0-6.0 μm

• Occurs singly or in pairs

• Optimal temperature: 37 ˚C

What it looks like on the agar:

• Whole Colony                                      Round

• Margin                                                 Smooth

• Elevation                                              Umbonate (slightly raised in the center)

• Color                                                   Light yellow/white

• Colony Texture                                    Moist

Biochemical tests: 

• Oxidase                                                negative

• Catalase                                               positive

• Methy Red                                           positive

• Voges-Proskauer                                 negative

• Simmons Citrate                                   usually negative

• H₂S                                                      negative

• Urea Hydrolysis                                    negative

• Reduction of nitrate                               positive

• Indole                                                   positive

• Lysine Decarboxylase                           positive

Interesting Facts:

• Occurs as normal flora in lower part of the intestine of warm-blooded animals

• Major cause of urinary tract infections and nosocomial infections

• Exhibits a metallic green color on the Eosin Methylene Blue (EMB) agar plate.