MicrobiologyLesson 2 of 2 in the course How We See the Invisible World

Specimen Staining and Specialized Microscopy in Microbiology

5 flashcards · 5 quiz questions · 5 match pairs · 4 fill-in sentences · English

Save course
Lesson progress
0 / 5

Your progress is kept in this browser only.Sign up to save it

Summary

Most cells and microorganisms are nearly colorless, so they can be difficult to distinguish from their surroundings under a light microscope. This lesson introduces the ways specimens are prepared and the basic principles behind dyes and staining.

A wet mount is prepared by placing a specimen in a drop of liquid on a slide and covering it with a coverslip. Liquid specimens, such as urine, can be transferred directly. A solid specimen, such as a skin scraping, can be placed on the slide and mixed with liquid. Wet mounts can be useful for observing living organisms and their movement, although cells may have little contrast without a stain.

All flashcards

What is a wet mount?
A preparation in which a specimen is placed in a drop of liquid on a slide and covered with a coverslip.
What does fixation do?
Fixation attaches cells to a slide, kills microorganisms, stops movement and metabolism, and helps preserve cellular components.
What is a chromophore?
The colored ion in a dye; the other ion is called the counterion.
How do positive and negative stains differ?
A positive stain colors cells or organisms; a negative stain colors the background and leaves cells relatively unstained.
How do simple and differential staining differ?
A simple stain uses one dye; a differential stain uses multiple reagents to distinguish organisms or structures.

Quiz questions

  1. Which sequence gives the four main steps of Gram staining in order?Answer: Crystal violet, iodine, decolorizer, counterstain.
  2. What is the key difference between the Ziehl-Neelsen and Kinyoun acid-fast methods?Answer: Ziehl-Neelsen uses heat during primary staining; Kinyoun does not.
  3. In the Schaeffer-Fulton method, what colors do endospores and vegetative cells appear?Answer: Endospores are green; vegetative cells are pink.
  4. Why is a specimen sputter-coated with metal for scanning electron microscopy?Answer: The conductive coating helps prevent charging from the electron beam.
  5. What can a Gram-stain result establish about a bacterium?Answer: It provides broad cell-wall classification, but does not identify a species or determine antibiotic susceptibility.

Based on Microbiology by Nina Parker, Mark Schneegurt, Anh-Hue Thi Tu, Philip Lister, Brian M. Forster (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

More in Microbiology

All Microbiology lessons
MicrobiologyBacterial Culture Media: Composition, Selection, and Differential Tests5 flashcards · 5 quiz questions · 4 gamesPlay free →MicrobiologyMicrobial Temperature Growth, Adaptations, and Food Safety5 flashcards · 5 quiz questions · 4 gamesPlay free →MicrobiologyClinical Features, Transmission, and Time Courses of Infectious Disease5 flashcards · 5 quiz questions · 4 gamesPlay free →MicrobiologyMicrobial Growth, Enumeration, Reproduction, and Biofilms5 flashcards · 5 quiz questions · 4 gamesPlay free →MicrobiologyDeeply Branching Bacteria: Phylogenetic Position and Extreme Adaptations5 flashcards · 5 quiz questions · 4 gamesPlay free →MicrobiologyFrom Ancient Fermentation to the Foundations of Microbiology5 flashcards · 5 quiz questions · 4 gamesPlay free →