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.