1. TRUE or FALSE. Relative to a 24 hour culture of endospore forming bacteria, a 72 hour culture would contain more endospores.

1. why is there a need to incubate cultures at room temperature? How can this affect microbes? 2. Explain why an inverted image is seen under a compound microscope.

12. A differential media  a) allows visual distinction between bacteria to perform a specific biochemical process b) inhibits the growth of certain bacteria c) will only grow Gram-negative bacteria d) is a selective media

Dilute cells from an old culture 1:200 into 5 mL of fresh media. What volume of the old culture would you add to the new media?

1. Which of the following is NOT true of spread plating method? A. the maximum inoculum allowed is 1.0 ml B. spreading of the inoculum is done using a disinfected glass L-rod C. A pre-solidified medium is required prior to inoculation of the sample. D. A and B   2. Plates inoculated with bacteria are inverted during incubation to: A. prevent contamination B. limit the colony growth C. A and B D.  A and C E. All of the above F. None of the above

1. If you are a thermophilic endospore forming bacterium what would be the appropriate and economically wise method for your preservation? Which culture collection centers will you select and why?

3. One gram of soil was suspended in 9 ml saline and thoroughly mixed. From this suspension, 4 serial, 1:10 dilutions were made. 200 hundred microliters of each of the last four serial dilutions were used for spread plating on TY media, resulting in 5600 colonies, 412 colonies, 54 colonies and 8 colonies. What do you calculate as the bacterial concentration in the soil? (For your information 1 gram = 1 ml)

1. What is the appropriate and economically wise preservation method for a thermophilic endospore forming bacterium? Discuss and explain it comprehensively, and please, do not just copy from somewhere. Choose among this methods: periodic transfer to fresh media, overlaying cultures with mineral oil, freeze-drying, cryopreservation, drying, sterile distilled water

2. You use tubes to test aerotolerance of bacteria. From your samples you have 3 results: A. Bacteria growing on the surface. B. Bacteria growing throughout the tube, the agar shows cracks. C. Bacteria growing about 5 mm below the surface. Please interpret each bacterial result. (Give the bacteria an oxygen classification, explain what classification means and interpret the cracks in the agar.)

1. The technique used in bacteria for endospore staining can also be used to observe fungal spores. Select one: True False 2.  Which of the following statements is/are TRUE?   a.   Agar does not provide nutrients to microorganisms.   b.   Peptone, pork extracts, and yeast extracts provide nutrients to microbes.   c.   Tap water must be used for preparing culture media.   d. A & B are correct. e. B & C are correct Clear my choice 3.  Motility of microorganisms is BEST observed with a   a. Flagellar stain b. Hanging drop preparation c. Solid medium d. Negative stain e. Streak plate Clear my choice