Bacteria

Question 1

Robert Hooke

Answer 1

Coined the term “cell” after observing plant cells in Micrographia (1665). First to describe microorganisms (mold on leather).

Question 2

Anton van Leeuwenhoek

Answer 2

“Father of Microbiology.” First to observe and describe bacteria (“animalcules”) using handmade microscopes (1676).

Question 3

Louis Pasteur

Answer 3

Disproved spontaneous generation with swan-neck flask experiments. Developed pasteurization, vaccines (rabies, anthrax), and germ theory.

Question 4

Gram Stain

Answer 4

Differentiates bacteria into Gram-positive (purple, thick peptidoglycan) and Gram-negative (pink, thin peptidoglycan + outer membrane).

Steps: Crystal violet → Iodine → Alcohol decolorizer → Safranin.

Question 5

Prokaryotic vs. Eukaryotic Cells

Answer 5

Prokaryotes: No nucleus, 70S ribosomes, peptidoglycan cell wall (e.g., E. coli).

Eukaryotes: Membrane-bound organelles, 80S ribosomes, cellulose/chitin cell walls.

Question 6

Symbiogenesis (Endosymbiotic Theory)

Answer 6

Mitochondria and chloroplasts evolved from engulfed prokaryotes (mitochondria = proteobacteria; chloroplasts = cyanobacteria).

Question 7

Carl Woese’s Tree of Life

Answer 7

Bacteria, Archaea, Eukarya (based on 16S rRNA sequencing).

Question 8

Bacterial Cell Wall

Answer 8

Gram-positive: Thick peptidoglycan + teichoic acids.

Gram-negative: Thin peptidoglycan + outer membrane (LPS endotoxin).

Question 9

Flagella Arrangements

Answer 9

Monotrichous: Single flagellum (e.g., Vibrio cholerae).

Peritrichous: Flagella all over (e.g., E. coli).

Question 10

What color do Gram-positive bacteria appear under a microscope after Gram staining?

Answer 10

Purple

Question 11

What are the two main classifications of Gram-positive bacteria based on shape?

Answer 11

Cocci (spherical) and bacilli (rod-shaped).

Question 12

What test differentiates between Staphylococci and Streptococci?

Answer 12

Catalase test

Question 13

What is the result of the catalase test for Staphylococci?

Answer 13

positive

Question 14

What is the result of the catalase test for Streptococci?

Answer 14

negative

Question 15

What enzyme converts hydrogen peroxide into water and oxygen?

Answer 15

catalase

Question 16

What test differentiates Staphylococcus aureus from other Staph species?

Answer 16

coagulase test

Question 17

Why do Staph aureus colonies appear golden?

Answer 17

due to carotenoid pigments

Question 18

Name two examples of coagulase-negative Staph.

Answer 18

Staph epidermidis and Staph saprophyticus.

Question 19

How are Streptococci arranged?

Answer 19

In chains or cords.

Question 20

What are the three types of hemolytic activity observed in Streptococci?

Answer 20

Alpha-hemolytic, beta-hemolytic, and gamma-hemolytic.

Question 21

Can gram-negative bacteria form endospores?

Answer 21

no

Question 22

what are endospores bound to

Answer 22

Calcium bound to dipicolinic acid

Question 23

What is required to kill spores?

Answer 23

Autocleaving

Question 24

What is the composition and function of the bacterial capsule?

Answer 24

Composition: Polysaccharide and polypeptide (“slime layer”).

Functions:

Protects against desiccation and phagocytosis.

Masks biomarkers (evades immune response).

Facilitates surface attachment (e.g., Streptococcus mutans in dental plaque, biofilms on catheters).

Question 25

Compare Gram-positive and Gram-negative bacterial cell walls.

Answer 25

Gram-positive: Thick peptidoglycan layer. No outer membrane. Gram-negative: Thin peptidoglycan layer. Outer membrane containing LPS (lipopolysaccharide).

Question 26

What is the primary function of the bacterial cell wall?

Answer 26

Maintains cell shape, prevents osmotic rupture, and contributes to pathogenicity.

Question 27

Name the four flagellar arrangements and their descriptions.

Answer 27

Monotrichous: Single polar flagellum. Lophotrichous: Tuft of flagella at one/both poles. Amphitrichous: Single flagellum at both poles. Peritrichous: Flagella distributed over the entire cell.

Question 28

How does chemotaxis guide bacterial movement?

Answer 28

Runs: Smooth movement toward attractants (e.g., nutrients). Tumbles: Random reorientation to change direction. Controlled by chemoreceptors detecting chemical gradients.

Question 29

Differentiate between fimbriae and pili.

Answer 29

Fimbriae: Short, hair-like; mediate adherence (e.g., E. coli in infections). Pili: Longer, fewer (1-2/cell); facilitate DNA transfer (conjugation).

Question 30

describe the bacterial chromosome and plasmids

Answer 30

Chromosome: Singl circular dsDNA molecule Plasmids: Small,circular, extra chromosomal DNA, carry antibiotic resistance genes.

Question 31

Why are bacterial ribosomes a target for antibiotics?

Answer 31

ribosomes are 70S, differing from eukaryotic 80S ribosomes. Antibiotics like streptomocyin exploit these differences

Question 32

Which bacteria produce endospores, and what triggers their formation?

Answer 32

Producers: Clostridium (e.g., C. tetani) and Bacillus (e.g., B. anthracis). Sporulation: Induced by nutrient deprivation; forms highly resistant spores. Germination: Returns to vegetative state under favorable conditions.

Question 33

Compare exotoxins and endotoxins

Answer 33

Gram positive produce exotoxins from proteins A-B subunits, Endotoxins LPS in gram negative cell walls.