Microbiology Flashcards
What are the ways we can classify bacteria?
Size, shape, staining characteristics, antigenic features
What does bacillus mean in terms of bacteria shape?
Rod shaped
What does coccus mean in terms of the shape of bacteria?
Spherical
What does spiral mean in terms of shape of bacteria?
Cork screw
Why do bacteria stain different colours?
Due to the different chemical composition of cell wall
What colour do gram positive turn when gram stained? Why?
Purple - thick layer of peptidoglycan
What is the first step of gram staining?
Crystal violet binds to the peptidoglycan layer
What is the 2nd step of gram staining?
Iodine complex binds crystal violet to peptidoglycan more strongly
What is the 3rd step of gram staining?
Gram negative lose their outer lipopolysaccharide layer and crystal violet and iodine complex is washed away
What’s the 4th step of gram staining?
Safranin (counterstain) turns gram negative red
What are some nutrients that are supplied in media that re required?
Carbon compounds, glucose, nitrogen, growth factors (minerals and vitamins)
What’s the definition of a obligate aerobe?
A microorganism/bacteria that grow in they presence of oxygen
What is the definition of an obligate anaerobe?
Microorganism/bacteria that grow in the absence of oxygen
What is the definition of a facultative anaerobe?
A microorganism/bacteria that can grow with or without oxygen
What is aseptic technique used to prevent?
Contamination of environment by microbes
Contamination of the culture by unwanted microbes from the environment
How do you prevent contamination to apparatus?
Sterile all apparatus, sterile work surfaces, handle carefully
What is an autoclave?
Sealed container where glass and metal equipment is sterile using heat
What temperature does the autoclave reach? Why? How long?
121 degrees, that’s when steam is produced, 15 minutes
Why is the autoclave in pressure?
Pressure helps the stream reach the equipment
When securing the Petri dish with tape, why not put it all the way around?
Anaerobe conditions could be created and the bacteria may be obligate aerobe
What is a viable count?
Living cells only (plating and counting colonies)
What is a total count?
Living and dead cells
Why do we serial dilute?
To produce clear and distinct colonies that aren’t clumped
