Microbiology Flashcards
Draw and label the structure of a gram-positive bacterium.
The structure of a gram-positive bacterium includes a thick peptidoglycan cell wall, cell membrane, cytoplasm, and a single circular chromosome.
Draw and label the structure of a gram-negative bacterium.
The structure of a gram-negative bacterium includes an outer membrane, thinner peptidoglycan cell wall, cell membrane, cytoplasm, and a single circular chromosome.
Name the molecule that makes up the cell wall.
The cell wall is primarily made up of peptidoglycan.
escribe an experiment to identify gram-positive and gram-negative bacteria. Include the results for each type and the chemicals added at each stage.
The Gram stain test is used for identification.
Steps:
Apply crystal violet stain.
Add iodine solution.
Rinse with ethanol or acetone.
Apply safranin counterstain.
Results:
Gram-positive bacteria retain the crystal violet and appear purple.
Gram-negative bacteria lose the crystal violet and take on the safranin stain, appearing pink.
Explain why the color changes are different for gram-negative and gram-positive bacteria.
The differences in color changes are due to variations in the structure of the cell walls. Gram-positive bacteria have a thick peptidoglycan layer that retains the crystal violet stain, while gram-negative bacteria have a thinner peptidoglycan layer and an outer membrane that allows the stain to wash away.
State the conditions necessary for bacterial growth.
Bacterial growth requires suitable temperature, pH, nutrients, moisture, and oxygen levels, as well as time for reproduction.
Describe what obligate aerobes, obligate anaerobes, and facultative anaerobes are.
Obligate Aerobes: These bacteria require oxygen for growth and cannot survive in its absence.
Obligate Anaerobes: These bacteria cannot tolerate oxygen and only grow in the absence of oxygen.
Facultative Anaerobes: These bacteria can grow in the presence or absence of oxygen and can switch their metabolic processes accordingly.
