Direct and indirect staining
SUBDOMAIN 211.2 – CLINICAL MICROBIOLOGY LABORATORY.
Competency 211.2.9: Techniques and Procedures – The graduate uses appropriate
techniques or procedures for interacting with microorganisms in a clinic, laboratory, or
community setting; utilizes basic laboratory techniques for identifying microorganisms;
demonstrates proper laboratory techniques in microbiology, including sterile technique,
staining techniques, aseptic technique, and chemical indicators; and recognizes types of
culture media and when to use each.
211.2.9-02: Demonstrate proper aseptic technique when performing specified tasks in the
211.2.9-05: Prepare a microscope slide for identification of a given microorganism.
211.2.9-08: Use a microscope to observe bacteria or blood samples in a laboratory setting.
211.2.9-09: Employ a specified bleach sterilizing technique in a laboratory setting.
211.2.9-10: Employ a specified preparation technique to observe a given bacterial
211.2.9-11: Employ a given direct or indirect staining technique in a laboratory setting.
Go to the lab manual in your Microbiology labpaq. Access “Experiment 2: Bacterial
Morphology.” Be sure to read the entire experiment and organize time, materials, and
workspace before beginning. Remember to review the safety sections and wear goggles
when working with chemicals.
In this lab you will demonstrate competency in the following areas:
Part 1: Viewing Prepared Slides of Common Bacterial Shapes
This section provides a review of bacterial morphology using prepared slides.
Part 2: Disinfecting Your Area to Use Live Organisms
This section discusses the importance of disinfecting the work area and teaches you to
prepare and effectively use a 30% bleach solution.
Part 3: Viewing Live Organisms—Wet-Mount Preparation
This section provides practice in making and viewing wet-mount preparations utilizing
Saccharomyces cerevisiae and epithelial cells.
Part 4: Direct Staining
This section provides an introduction to direct staining techniques using crystal violet. You
will make and stain preparations of S. cerevisiae, epithelial cells, and dental plaque.
Part 5: Indirect Staining
This section expands on the previous by using Congo Red as an indirect stain. You will make
and stain preparations of S. cerevisiae, epithelial cells, and dental plaque, which are
compared to the slides stained with crystal violet.
Note: You will use the Virtual Microscope to complete the lab activities. No actual
microscope will be needed to complete the lab activities.
Upon completion of the lab, write a brief essay (suggested length of 1–2 pages) in which
A. Compare your observations from the four activities of fresh wet mount, direct staining
using crystal violet, and indirect staining using both Congo Red and crystal violet.
B. Discuss whether you were able to identify specific bacterial morphologies.
C. Explain the difference between direct and indirect staining.
1. Discuss whether the smears appeared different in each type of staining.
a. Explain why the smears did or did not appear different in each type of staining.
D. Explain the similarities and differences between the cells in the plaque and those in the
E. Describe the size and shape of the types of cells that you were able to see in the smear
from your mouth.
Note: Address things such as whether cells appear to be independent or connected to
other cells somehow, and if the shape of the cell predicts the function of the cell.
F. When you use sources, include all in-text citations and references in APA format.
Note: For definitions of terms commonly used in the rubric, see the attached Rubric Terms.
Note: When using sources to support ideas and elements in a paper or project, the submission MUST include APA formatted in-text citations with a corresponding reference list for any direct quotes or paraphrasing. It is not necessary to list sources that were consulted if they have not been quoted or paraphrased in the text of the paper or project.
Note: No more than a combined total of 30% of a submission can be directly quoted or closely paraphrased from sources, even if cited correctly. For tips on using APA style, please refer to the APA Handout web link included in the General Instructions section. Here are some helpful APA resources: