Rhizoid Colony Formation

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 non-

diffusable 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.

Lenticular cloud

Lenticular Cloud over Mt. Shasta

Lenticular: Shaped like a double convex lens.Lenticular sproangia of Physarum viride

Umbonate

Colony Edge patterns

Pellicle floating on broth

Paramecium feeding on flocculent bacterial mass.

Filamentous Bacteria in a Hot Spring

The End