The microbial world

Question 1

Theoretical basis for the gram stain

Answer 1

1. The peptidoglycan barrier of gram negative bacteria is thinner and has a higher lipid and lower peptidoglycan content relative to gram positive bacteria.
2. Addition of solvent solubilizes the lipids and enhances the leaching of crystal violet into the solution in the case of gram negative bacteria. Conversely, in the case of gram positive bacteria, the solvent dehydrates the thicker cell wall closing pores and preventing the leaching of crystal violet into the solvent.

Question 2

Structural Features of a bacterial cell

Answer 2

• Nucleoid region: Where DNA or genetic material is found. Bacterial chromosomes are long circular supercoiled DNA molecule
• Ribosomes free in cytosol
• Plasmids

Question 3

Endospores

Answer 3

• Durable, dormant form of the cell
• Utilised as a way to store genetic information in times of stress
• Present only in a small number of gram positive bacteria

Question 4

Fungi

Answer 4

• Classified as eukaryotes (have membrane bound nucleus)
• cell membrane contains ergosterol as a replacement for cholesterol
• Cell wall is structurally and biosynthetically unique making it an attractive drug target

Mycoses (Systematic, superficial or subcutaneous) name for infection