The pictures were given in black and white. 5. (6 pts) Two of the following pict

Question

The pictures were given in black and white.

5. (6 pts) Two of the following pictures are of Gm* organisms and two are of Gm organisms. One of the Gm organisms is the spirochete Cristispira A simple stain called India ink was used to help visualize the glycocalyx of the cells in one of the pictures, and no staining was used to visualize endospores in the cells in another picture. Which pictures show the Gm organisms? Which picture shows the sample stained with India ink? What type of microscopy was most likely used to generate each picture? (be as specific as possible) Outer Periplas 0

Explanation / Answer

Picture B shows gram positive rod shaped organisms producing endospores.

Picture C shows sample stained with India ink. The glycocalyx layer do not take up India ink and remain as clear halos that surrounds bacterial cell.

A. Picture A shows electron microscopy of cell wall structure of gram negative bacteria. Gram negative organisms have cell membrane made up of thin peptidoglycan layer. Between the outer peptidoglycan cell membrane and inner cytoplasmic membrane there is a characteristics space in gram negative organisms which is called as periplasmic space and it is filled with gel like matrix called periplasm. The structures can be seen more acurately under TEM or transmission electron microscopy.

B. Picture B shows phase contrast microscopy of endospore forming gram positive organisms mostly bacillus. Endospores are dormant asexual spores of bacteria which can survive in extreme conditions like temperature, nutrient deficient etc.

C. Picture C shows light microscopy of glycocalyx ( capsule ) staining of organisms by India ink method . The light microscope had been set in dark field to create contrast so that the capsular organism can be seen against the dark background.The glycocalyx is made up of glycoprotein or glycolipid which resists phagocytosis.

D. Picture D shows electron microscopy of spirochetes mostly SEM or scanning electron microscopy.

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