Lab 2: Aseptic Technique And Staining Cultures Flashcards
What is the primary goal of a microbiologist when studying a microbe?
To isolate a microbe from mixed cultures and grow the isolate in pure culture.
What technique is essential to prevent contamination in microbiological work?
Aseptic technique.
What are the necessary tools for working with pure cultures?
Sterile growth media and implements.
What is the purpose of a Bunsen burner in a research laboratory?
To flame and sterilize inoculating loops and culture tube openings.
What specialized equipment may be found in research laboratories for microbiology?
Biological safety cabinets and anaerobic chambers.
True or False: Smaller veterinary clinics can perform many basic microbiological tests without specialized equipment.
True.
What is the streak plate method used for?
To spread out microbial cells to the point where single cells can grow into isolated colonies.
How can microscopy be used in the characterization of bacterial cultures?
By examining cell morphology in wet mount preparations.
What staining technique is extensively used in diagnostic microbiology?
Gram stain.
Who invented the Gram stain technique and when?
Hans Christian Gram in 1882.
What does the Gram stain distinguish between?
Gram-positive and Gram-negative bacteria based on their cell wall properties.
What color does crystal violet stain all cells in the Gram stain procedure?
Blue.
What role does iodine play in the Gram stain procedure?
It serves as a mordant, forming a complex with crystal violet inside cells.
How do Gram-negative bacteria react to the decolorization step?
They are decolorized with alcohol.
What is the purpose of safranin in the Gram stain procedure?
It acts as a counterstain, giving a pink color to decolorized Gram-negative cells.
What factors can lead to false negative results in Gram staining?
Culture age, too short an incubation with crystal violet, missing the mordant step, or over-decolorizing.
What can cause false positive results in Gram staining?
Thick culture smears or under-decolorization.
What should you do at the beginning of every lab class?
Clean your lab table with antiseptic wash.
What is the first step in preparing a bacterial smear slide?
Place a tiny drop of water on a clean glass slide.
How do you heat-fix cells on a slide?
By passing the slide over the flame of an alcohol burner three times.
Fill in the blank: The Gram stain procedure involves covering the smear with _______ for 40-60 seconds.
Crystal violet
What should you do with your NA plate after streaking?
Incubate it upside down at 37°C.
What is NA medium?
An undefined rich agar medium containing amino acids, peptides, vitamins, and glucose.
What is the purpose of swirling the Petri dish after pouring NA medium?
To evenly distribute the agar medium.
