Gram staining & Morphology
What color do Gram-positive bacteria stain?
Purple
Prokaryotes lack what major cell structure?
A nucleus
What media is commonly used to grow Gram-positive organisms?
CNA or PEA agar
Define “normal flora.”
Microorganisms normally found on/in the body
What PPE is required for handling specimens?
Gloves, lab coat, and sometimes goggles
Name the shape of Staphylococcus aureus.
Cocci in clusters
What is the term for bacteria that require oxygen?
Aerobes
What plate is selective for Gram-negative rods?
MacConkey agar
Give an example of pathogenic Gram-positive cocci.
Staphylococcus aureus or Streptococcus pyogenes
What biosafety level are most clinical labs?
BSL-2 ( Biosafety Level 2 )
What chemical makes Gram-positive cells retain crystal violet?
Thick peptidoglycan layer
Name one genus of Gram-negative cocci.
Neisseria
What does a pink colony on MacConkey agar indicate?
Lactose fermentation
Where is E. coli considered normal flora?
The intestines
How long should hands be washed after glove removal?
At least 20 seconds
Gram-negative rods appear what color and shape?
Pink, rod-shaped bacilli
What structure helps bacteria move?
Flagella
What method is used to isolate single colonies on a plate?
Streak plate technique (quadrant streaking)
What term describes bacteria that cause disease only when the host is weakened?
Opportunistic pathogens
What is the correct way to dispose of contaminated plates?
Biohazard waste container
What is the purpose of the iodine (mordant) in the Gram stain process?
It binds with crystal violet to form a CV–iodine complex that helps trap the dye in Gram-positive cells.
What is the difference between an obligate anaerobe and a facultative anaerobe?
Obligate anaerobe: Cannot survive in oxygen.
Facultative anaerobe: Can grow with or without oxygen.
What type of hemolysis appears as complete clearing around colonies, and name one organism that shows it.
Beta hemolysis
What is the term for a disease-causing organism that originates from the patient’s own normal flora?
Endogenous infection
What is aseptic technique, and why is it essential in a microbiology lab?
A set of procedures used to prevent contamination of samples, the environment, and the microbiologist; ensures accurate results and safety.