Media

Media

1. Broth Culture

   • moderate turbid/floccuent growth
   • heavy turbid/flocculent growth
   • heavy sediment growth
   • heavy pellicle/ring growth
   • key terms
     • inoculum
     • chromogensis
     • continous cloudy (turbid) appearance common
     • loose aggregate of cells at bottom of culture tube is sediment; tighter group is a button
     • pellicle - continuous layer across the surface
     • flocculent growth - tiny, fuzzy clumps floating in the broth
   • incubation at 37C for 24 hours

2. Agar Slant Culture

   • slant morphologies include no growth, rhizoid (hair-like), filiform (even; most common) and beaded
   • Agar slants made by adding dissolved agar media to test tubes and allowed to cool at a tilted angle
   • factors that affect growth: air/oxygen, temperature, lighting, pH, osmotic conditions

3. Pure Culture - Streaking for Isolation

   • colony morphological forms: punctiform, filamentous/rhizoid, circular, spindle (lens)
   • colony elevation types: flat or raised
   • colony margin types: entire (even), undulate (wavy), filamentous, lobate (uneven), curled, swarming
   • correct way to incubate a Petri dish is to invert the dish with cover side down
   • note keys to identification: colony appearance, Gram reaction, specific metabolic reactions, antibiotic sensitivity

4. Kligler's Iron Agar

5. Phenol Red Broths

6. Blood Agar to detect Hemolysis

   • some microbes produce exoenzymes that can completely or partially destroy hemoglobin in red blood cells in the media; a hemolysis the completely destroys the hemoglobin creates a clear zone around the colony. Note: fastidious organisms need growth factors
     • beta hemolysis - complete, clear (transparent) edges
     • gamma hemolysis - no hemolysis at all; no or little change to agar
   • alpha hemolysis - incomplete, holding the plate up to light and a greenish color
   • hemolysin: is an exoenzyme (exo-outside cell)