Bacteria

Question 1

Basic bacteria information

Answer 1

• Single celled (prokaryotic)
• Large domain: microorganisms
• Among life lift forms on Earth
• Present in most habitats on Earth

Question 2

Shapes of bacteria

Answer 2

1. Spherical (cocci)
2. Rod-shaped (bacilli)
3. Spiral-shaped (spirochetes)

Question 3

Cell Wall

Answer 3

• Nearly all prokaryotes have it
• Maintains shape
• Protection
• Prevents bursting
  Gram stain can determine the type of bacteria

Question 4

What’s the difference between Gram + and -

Answer 4

Gram +
- Simpler cell walls + more peptidoglycan (polymer, sugars + amino acids that forms a mesh-like layer outside plasma membrane)
- Target of many antibiotics
- Violet colour
Gram -
- Less peptidoglycan, outer membrane made of lipopolysaccharides (can be toxic)
- Less affected by antibiotics
- Red colour

Question 5

Capsule

Answer 5

• Made of protein or polysaccharides
• Located either outside: 1) the peptidoglycan layer (gram +) or 2) the lipopolysaccharide layer (gram -)
• Anti-phagocytic
• Protects against desiccation
• Helps adhere to surfaces
• Protects anaerobic bacteria from O2
• Protects against viruses

Question 6

Fimbriae

Answer 6

• Some bacteria stick to surfaces / substrates through hair-like appendages called fimbriae
  *Can be used to create biofilm

Question 7

Pili

Answer 7

• Appendages that pull two cells together to allow DNA transfer from one cell to another

Question 8

Flagella

Answer 8

• Enables movement (up to 50 um/sec)
• Can be scattered or condensed on either or both ends

Question 9

Specialized Membranes

Answer 9

• Performs metabolic functions

Question 10

DNA

Answer 10

• Less DNA than eukaryotes
• Mostly single, circular chromosome (nucleotide)
• Sometimes there is a smaller circular DNA molecules = plasmids

Question 11

Genetic Variation: Rapid Reproduction

Answer 11

• Bacteria reproduce by binary fission: splitting of organism into two genetically identical organisms
• Mutations can happen, less common in binary fission, but because it is rapid (sometimes under 10 mins) it can lead to mutations
  *Probability of mutation in a gene for E. Coli is 1 in 10 million but when 20 billion new bacteria are created in a person’s intestine every day (there are 4,300 genes meaning that 8.4 million mutations happen every day per human host)

Question 12

Genetic Variation: Genetic Recombination

Answer 12

• Combining two genetic sources
• Horizontal movement (sometimes lateral)
• Bacteria is brought together through three ways:
  1. Transformation: foreign DNA is taken up by the environment and incorporated into the cell
  2. Transduction: Bacteriophage carry prokaryotic gene from one host cell to another
  3. Conjunction: DNA is transferred between two bacteria (usually same species) that are temporarily joined via sex pilus

Question 13

Interactions: Mutualism

Answer 13

Example 1: Nitrogen fixing
- Plants cannot directly take N2 from the atmosphere
- Certain bacteria converts N2 to ammonia which is used by the plants for functions
Example 2: Microbiome and humans
- Human gut has trillions of bacteria
- Functions: digestion of breast milk, fiber, etc… helps immune system, produces vitamins, influences brain and behaviour

Question 14

Interactions: Parasitism

Answer 14

Example 1: Borrelia = Lyme Disease
Example 2: Mycobacterium tuberculosis = tuberculosis
*Approx. half of human diseases are from bacteria… and bacteria is becoming antibiotic resistant
BUT some infections create a stronger immune system in offspring (epigenetics): e.g. seen in mice