Transcript Bacteria Plating and Morphology

Colony Morphology
E. coli
• medium sized
colonies
• regular margin
• convex elevation
Klebsiella pneumoniae
• Slightly gummy/wet
looking colonies
• Circular
• convex
• entire margin
Bacillus subtilis. These gram positive, sporeforming rods produce
colonies which are dry, flat, and irregular, with lobate margins.
Pseudomonas aeruginosa. This gram negative rod forms mucoid colonies with
umbonate elevation. Some strains produce a diffusable green pigment and a
distinctive fruity odor. P. aeruginosa is an opportunistic contaminant of burn
injurys, wounds such as cuts and gunshot, and can cause bacterial
pneumonia. It is often nosocomial pathogen, easily transmitted by hands and
invasive medical procedures.
Salmonella choleraesuis serovar typhimurium. This gram negative rod is a
component of the gastrointestinal tract of birds and reptiles and is an agent of
gastroenteritis in humans. It forms shiny, convex colonies with entire margins.
Escherichia coli. This gram negative rod (coccobacillus) forms shiny, mucoid
colonies which have entire margins and are slightly raised. Older colonies
often have a darker center.
Rhodospirillum rubrum. Pinpoint circular colonies which are convex
with entire margins. This gram negative spirillum produces a nondiffusable red pigment.
Micrococcus luteus. Circular, pinhead colonies which are convex with
entire margins. This gram positive coccus produces a bright yellow,
non-diffusable pigment
Staphylococcus aureus. Circular, pinhead colonies which are convex with
entire margins. This gram positive coccus often produces colonies which have
a golden-brown color.
Staphylococcus epidermidis. Circular, pinhead colonies which are convex with
entire margins. The colonies of this gram-positive coccus appear either the
color of the agar, or whitish.
Bacillus subtilis
• Colonies large
• margin is undulate or
lobate
• dry
• with circular form
• flat elevation
Staphylococcus aureus.
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•
•
•
Circular
Pinhead
Convex
Entire margin
Serratia marcescens
• Mucoid
• Entire margin
• Umbonate
elevation
• Red and white
colonies