21. What is the major reason for performing a TS 22. How are TSl tubes inoculate

Question

21. What is the major reason for performing a TS 22. How are TSl tubes inoculated? 23. If an organism can ferment glucose, but NOT lactose or sacrose, after 24 hours, what color will the "slan of the TSI tube be? 24. If an organism can ferment glucose, but NOT lactose or sacrose, after 24 hours, what oolor will the "but" of the TSI tube be? 25. Why do lactose fermenters and sucrose fermenters produce more acid in TSI tubes than organisms that can only ferment glucose? 26. A black butt in a TSI tube indicates that the organism is able to perform what TWO DIFFERENT metabolic activities?

Explanation / Answer

ans 1- TSI test is done to know whether the organism is capable of fermenting which sugar and its ability to produce H2S. it is utilized to distinguish among gram-negative pathogens on the basis of their ability to ferment carbohydrates viz. sucrose, glucose, and lactose.

ans 2- solid slants are prepared in test tubes; first, the inoculating needle with inoculum is stabbed through the surface till bottom then the inoculum is streaked on the surface of the slant.

ans 3 and 4- Red Slant/Yellow Butt due to the presence of more glucose at butt due to less amount of glucose on the slant the little acidic change will be neutralized by oxidation and thus slant will remain red due to alkalinity on the surface.

ans 5- due to the large quantity of both sucrose and lactose in medium (10x higher than glucose) organism rapidly utilize them and produce more acid than utilizing glucose alone.

ans 6- two different metabolic activities exhibited by such organism is:- a) fermentation of carbohydrates; b) breakdown of amino acids present in the medium which results in H2S gas which reacts with iron present in medium and produces the black color.

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