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Question: physieal agents of control environmental osmotic pressure the generic circle...

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Physieal Agents of Control: Environmental Osmotic Pressure The generic circle represents a cell -consider it to be a bacterial cell Beaker C Beaker A Beaker B Immediately after cell is placed into beaker No net movement of water Net movement of water out of cell of water into cell A couple of minutes later Cel swells No eect Cel collapses Figure 1 Osmotic environments 3. Using aseptie technique, inoculate each of the agar plates with the three experimental organisms by making a single-line loop inocu- lation of each organism in its appropriately labeled section. Incubate all plates in an inverted position for 4 to 6 days at 26C Media Per designated student group: one nutrient agar plate of each of the following sodium chloride concentrations: 085%, 5%, 10%, 15%, and 25%. 4. Equipment Bunsen burner, inoculating loop, and glassware marking pencil Procedure Lab Two 1. Observe each of the nutrient agar plate cul- Procedure Lab One tures for the amount of growth on each of the 1. Mark the underside of each of the five nutri- ent agar plates into three sections with a glassware marking pencil. Label each of the three sections on each plate with the name of the organism to be inoculated. 2. 16
1/8/2019 014. In the lab info it says that as a rule, most microbes can adjust to a range of salt concentrations Which cell structure allows microbes to physically withstand hypotonic environments? MSA has two properties. It is both selective and differential. When bacteria grow on this media, there is a visible difference between bacteria that ferment mannitol, and the bacteria that do not. See Figure 2 (a)- effects of selective/differential media. Q15. Which of the following is correct about MSA? a) Species of Staphlycoccus grow on this medium and some produce a yellow halo indicating they ferment mannitol coccus grow on this medium and all produce a yellow halo since they ferment mannitol c) The pH indicator phenol red tums yellow when the pH increases d) E coli grows very well on this medium and will appear pinkishred since it ferments lactose In addition to solutes other chemicals are used to affect the growth of bacteria. One example is phenylethyl alcohol which affects certain bacterial cell walls and can be used to make a selective medium. Look at Figure 1 which shows how E. coli and S.aureus grow on phenylethyl alcohol (PEA) agar compared to nutrient agar. 016. TF PEA shows a complete inhibition of the growth of E.coli Eosin-methylene blue agar (EMB) contains compounds that partially inhibit gram positive organisms AND allow a difference to be seen for the bacteria that do grow. FYI, the book shows only one bacterium growing on an EMB plate. Q17. T/F Escherichia coli and Enterobacter aerogenes colonies will look the same on EMB, you will not be able to tell them apart Blood agar does not have compounds to select for or against bacteria but differences can be seen when bacteria grown on blood agar. Q18. Which type of hemolysis shows the least change on blood agar? a. alpha b. beta c. gamma Use the 5 functions of special-purpose media listed to answer 19 and 20 Q19. T/F The first function applies to medicine since it is important to separate disease causing bacteria from other bacteria. For example, from a fecal specimen. Q20. T/F The last function applies to differential media.
Principle Numerous special-purpose media are available to do the following: 1. Isolation of bacterial types from a mixed population of organisms. Differentiation among closely related groups of bacteria on the basis of macroscopic appearance of the colonies and biochemical reactions within the medium. Enumeration of bacteria in sanitary micro- biology, such as in water and sewage, and also in food and dairy products. Assay of naturally occurring substances, including antibiotics, vitamins, and products of industrial fermentation. Characterization and identification of bacteria by their abilities to produce chemical changes in different media. 2. 3. 4. 5.
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