BISC209/S11: Lab8

Culturable Bacteria Isolates Characterization continued

Complete Quorum Sensing & Mutualistic and Antagonistic Interactions Tests set up last week

Take photos of your plates.

Complete Antibiotic Production & Sensitivity Testing
Week 3

• Examine the plates and look for evidence of inhibition of growth of "test" organisms near the putative antibiotic producer's midline streak. This will appear as a measurable zone of inhibition (section of a circle of no growth). You should measure the radius of the area most affected and convert to diameter in millimeters of inhibition. The size is indicative of the diffusion potential of the antibiotic and/or an indication of how sensitive the test organism is to the mechanism of inhibition. Compare your results to other tested isolates in your lab. Think about why an antibiotic might work differently on a Gram positive vs. a Gram negative organism or between two bacteria that are both Gram positive.
• Take a photo of your plates. If you found no inhibition of growth, does that mean that your potential antibiotic producer does not secrete any antimicrobial compounds? Why or why not?

Special Stains:
Perform appropriate special stains as indicated. All isolates growing from your dried soil extract on Glyerol Yeast Extract Agar (GYEA) medium that are potential spore formers should be stained for endospores.
Directions for stains are found in the Protocols section of the wiki.
Stains : Simple, Gram, Endospore, Capsule, and Motility Tests
All Gram positive bacilli or any bacteria that showed unstained area in the cells when Gram stained should be stained for endospores.

Perform confirmatory testing for motility. Directions for the Hanging Drop and Flagella stain can be found in the Motility Tests section of the Protocols.

All bacteria that were positive or ambiguous for motility in SIMs medium should be looked at by Hanging Drop technique; if positive by Hanging drop, you could try the Flagella stain. All the "swarmers" (those bacteria that spread all over the plate)should be looked at by Hanging Drop too.

Highly mucoid (sticky and wet) colonies should be tested for the presence of a capsule using the capsule stain protocol.

If your Gram stain results were ambiguous or not what you expected from growth on PEA and EMB you used, you should probably repeat those Gram stains.

Assignment

Graphical abstract: See models in research reports found in recent issues of the journal Cell

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