Bacteria Flashcards
Robert Hooke
Coined the term “cell” after observing plant cells in Micrographia (1665). First to describe microorganisms (mold on leather).
Anton van Leeuwenhoek
“Father of Microbiology.” First to observe and describe bacteria (“animalcules”) using handmade microscopes (1676).
Louis Pasteur
Disproved spontaneous generation with swan-neck flask experiments. Developed pasteurization, vaccines (rabies, anthrax), and germ theory.
Gram Stain
Differentiates bacteria into Gram-positive (purple, thick peptidoglycan) and Gram-negative (pink, thin peptidoglycan + outer membrane).
Steps: Crystal violet → Iodine → Alcohol decolorizer → Safranin.
Prokaryotic vs. Eukaryotic Cells
Prokaryotes: No nucleus, 70S ribosomes, peptidoglycan cell wall (e.g., E. coli).
Eukaryotes: Membrane-bound organelles, 80S ribosomes, cellulose/chitin cell walls.
Symbiogenesis (Endosymbiotic Theory)
Mitochondria and chloroplasts evolved from engulfed prokaryotes (mitochondria = proteobacteria; chloroplasts = cyanobacteria).
Carl Woese’s Tree of Life
Bacteria, Archaea, Eukarya (based on 16S rRNA sequencing).
Bacterial Cell Wall
Gram-positive: Thick peptidoglycan + teichoic acids.
Gram-negative: Thin peptidoglycan + outer membrane (LPS endotoxin).
Flagella Arrangements
Monotrichous: Single flagellum (e.g., Vibrio cholerae).
Peritrichous: Flagella all over (e.g., E. coli).
What color do Gram-positive bacteria appear under a microscope after Gram staining?
Purple
What are the two main classifications of Gram-positive bacteria based on shape?
Cocci (spherical) and bacilli (rod-shaped).
What test differentiates between Staphylococci and Streptococci?
Catalase test
What is the result of the catalase test for Staphylococci?
positive
What is the result of the catalase test for Streptococci?
negative
What enzyme converts hydrogen peroxide into water and oxygen?
catalase
What test differentiates Staphylococcus aureus from other Staph species?
coagulase test
Why do Staph aureus colonies appear golden?
due to carotenoid pigments
Name two examples of coagulase-negative Staph.
Staph epidermidis and Staph saprophyticus.
How are Streptococci arranged?
In chains or cords.
What are the three types of hemolytic activity observed in Streptococci?
Alpha-hemolytic, beta-hemolytic, and gamma-hemolytic.
Can gram-negative bacteria form endospores?
no
what are endospores bound to
Calcium bound to dipicolinic acid
What is required to kill spores?
Autocleaving
