MCB 3020 Lecture Notes - Lecture 6: Piezophile, Pyrimidine Dimer, Deinococcus Radiodurans
Document Summary
Basis of different oxygen sensitivities: oxygen easily reduced to toxic reactive oxygen species (ros) Hydroxyl radical: aerobes produce protective enzymes. Strict anaerobic microbes: all strict anaerobic microorganisms lack or have very low quantities of. Catalase: these microbes cannot tolerate o2, anaerobes must be grown without o2. Pressure: microbes that live on land and water surface live at 1 atmosphere (atm, some bacteria and archaea live in deep sea with very high hydrostatic pressures, barotolerant. Adversely affected by increased pressure, but not as severely as nontolerant organisms: barophilic (peizophilic) organisms require or grow more rapidly in the presence of increased pressure. Change membrane fatty acids to adapt to high pressures. Disrupts chemical structure of many molecules, including dna. Damage may be repaired by dna repair mechanisms if small dose. Extremely resistant to dna damage: ultraviolet (uv) radiation. Wavelength most effectively absorbed by dna is 260 nm. Causes formation of thymine dimers in dna requires direct exposure on microbial surface.
