Question

Eosin Methylene Blue (EMB) Ex. 4.6 16. What is the selective agent in this test? What is the differential agent in this test? 17. E. Coli produces a green metallic sheen when grown on an EMB plate. Why is this? If a pink color is produced by bacteria grown on this plate, what does that indicate? Phenol Red Broth Ex. 5.3 18. What purpose did the uninoculated controls serve in this test? After inoculation, what does a yellow result mean? A pink or magenta color mean? 19.what purpose does the durham tube serve? If gas bubbles are present, where did they come from? acBook Pro

Answer 1

16) selective agents for Eosin Methylene Blue Agar : Eosin Y and methylene blue dye

Differential agents for Eosin Methylene Blue Agar:  lactose and sucrose

17)

Eosin methylene blue agar (EMB) is a selective and differential medium used to isolate fecal coliforms.

Eosin Y and methylene blue are pH indicator dyes which combine to form a dark purple precipitate at low pH; they also serve to inhibit the growth of most Gram positive organisms.

Sucrose and lactose serve as fermentable carbohydrate sources which encourage the growth of fecal coliforms and provide a means of differentiating them.

Vigorous fermenters of lactose or sucrose will produce quantities of acid sufficient to form the dark purple dye complex. The growth of these organisms will appear dark purple to black and ften produces a green metallic sheen. Slow or weak fermenters will produce mucoid pink colonies.

19) Durham is used in microbiology to detect production of gas by microoraganism.A tube is fillled with solution in which microorganism to be grown and ferment that solution produce gas bubbles.