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Explain why all the bacteria grow so poorly in SIB? (1) SIB is an inorganic synthetic broth in which bacteria is a heterocyclic organism that require organic compounds for their energy source and their carbon. 4. Why are some organisms said to be fastidious? (1) Some organisms are said to be fastidious because an organism relies heavily on the environment to supply ready-made organic compounds. Organisms that are said to be fastidious have specific nutritional requirements. 5.

Complete the first two columns of the table below by referring to your results n page 103. Some media are selective only, some are differential only and others are both selective and differential. State the specific selective and/or differential purpose of each of the following media, by completing the table. (If the medium is not selective or not differential, say so. ) (21) Medium Type of organisms that grew Type of organisms inhibited Selective for Differentiates between Penitently alcohol agar Gram-positive Gram-negative Not differential Crystal violet agar 7. % sodium chloride agar Holographic organisms Non-holographic Halogens staphylococci) Imitation salt agar Holographic organisms (staphylococci) Bacteria other than staphylococci (non-holographic) Halogens (staphylococci) Imitation-ferments and staphylococci that do not ferment imitation. McCracken differential Eosin-methyl blue agar Differential Blood agar Streptococcal organisms (fastidious) none Not selective Hemolytic activities (zone of hemolytic) which allows foe beta hemolytic streptococci to be differentiated from other streptococci 6.

Describe the precise chemical (or physical) reactions that produce these tatters of bacterial growth in each case. (That is, say WHY these results occur). Some of the information is available in your lab manual but for others you may have to do some research to find out the answers. Description of chemical or physical reaction E. Arrogates colonies on EMBED are pink E. Arrogates ferments lactose in the medium to produce acid. This lowers the pH and the dyes in the medium it turn pink PEA prevents gram negatives from growing PEA prevents the growth of Gram-negative organisms by disrupting the structure f lipids in the Gram-negative membrane.

It also can hamper protein synthesis. Hemolytic is displayed on blood agar plates On the plate the bacteria produces enzymes called homologies these enzymes else the red blood cells to certain degrees. Bacteria the fully else the blood go through beta-hemolytic. Bacteria that partially else the blood go through alpha- hemolytic, and bacteria that doesn’t else at all goes through gamma hemolytic.

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