Discover the Fascinating World of Bacteria with Gram Staining!

What color would you expect Salmonella and Streptomyces to be following a gram stain?

a. Salmonella colorless & Streptomyces pink

b. Salmonella pink & Streptomyces purple

c. Salmonella purple & Streptomyces colorless

d. Salmonella purple & Streptomyces pink

Answer:

Following a gram stain, Salmonella would appear pink or colorless, while Streptomyces would appear purple. Hence the correct option is (b).

Gram staining is a technique used to classify bacteria based on their cell wall structure. It involves the use of crystal violet dye, iodine, alcohol, and safranin. The process consists of several steps:

• The bacteria are first stained with crystal violet, which colors all the cells purple.
• Iodine is then added, forming a complex with the crystal violet dye and trapping it inside the gram-positive bacteria.
• The slide is washed with alcohol or acetone, which acts as a decolorizer.
• Gram-positive bacteria retain the crystal violet dye and appear purple, while gram-negative bacteria do not retain the dye and appear pink or colorless.
• A counterstain, such as safranin, is applied to the slide to color the gram-negative bacteria.

In the case of Salmonella, which is a gram-negative bacterium, it would appear pink or colorless following a gram stain. On the other hand, Streptomyces, which is a gram-positive bacterium, would appear purple.

Gram staining is a fundamental technique in microbiology and plays a crucial role in the identification and classification of bacteria. By understanding the color changes that occur during gram staining, scientists can differentiate between gram-positive and gram-negative bacteria, aiding in diagnosis and treatment of various bacterial infections.