Question

1. gram-negative bacteria retain the purple color of crystal violet after decolorization.
2. when using aseptic technique, it is acceptable to touch the inside of the test tube cap with your fingers.

biol 2120
gram staining homework

1. heat fixing a bacterial smear kills the bacteria and adheres them to the slide.

Explanation:

Question 5

In Gram staining, Gram - negative bacteria have a thin peptidoglycan layer. After decolorization with alcohol/acetone, the crystal violet - iodine complex is washed out, and they take up the counterstain (safranin) and appear red. Gram - positive bacteria retain the purple color of crystal violet after decolorization. So the statement "Gram - negative bacteria retain the purple color of crystal violet after decolorization" is false.

Aseptic technique aims to prevent contamination. Touching the inside of the test tube cap with fingers can transfer contaminants (like bacteria from the skin) into the test tube, which is against aseptic principles. So the statement "When using aseptic technique, it is acceptable to touch the inside of the test tube cap with your fingers" is false.

Heat fixing involves passing the slide with the bacterial smear through a flame. This process kills the bacteria and also causes the bacterial cells to adhere to the slide, so that they do not wash off during the staining procedure. So the statement "Heat fixing a bacterial smear kills the bacteria and adheres them to the slide" is true.

Answer:

False

Question 6