140 - Topic 6 Notes

19 psychrophiles low temperature optima mesophiles

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Unformatted text preview: oom temperature. Their intolerance to heat is due to the denaturation of some of their enzymes at even moderate temperatures. As expected, the cytoplasmic membranes of psychrophiles are more fluid at low temperatures, and this is due to a greater proportion of unsaturated fatty acids in the membrane phospholipids. High Temperature Growth Thermophiles: optimal growth temperature above 45C Fundamentals of Microbiology (Biology 140) Course notes Dr. Josh D. Neufeld Hyperthermophiles: optimal growth temperature above 80C Examples of hot environments include: soil surface in midsummer sun: 50C compost piles: 65C hot springs: boiling point of water (100C) ocean floor hydrothermal vents: 350C hot water heaters: ~50C Archaea are the most thermophilic of all organisms, followed by bacteria, and then by eukaryotes (see Table 5.1). For thermophiles and hyperthermophiles to survive and thrive at high temperatures, their proteins must be resistant to thermal denaturation (i.e. thermostable). Their membrane phospholipids must also have a high proportion of saturated fatty acids (for the bacterial thermophiles) or lipid monolayer (for the archaeal hyperthermophiles Figure 3.7). Enzymes from thermophiles and hyperthermophiles are valued for their use in industrial processes, which are often preferentially carried out at high temperatures. Growth at Low or High pH Acidophiles: pH optimum between 2 and 6 Neutrophiles: pH optimum between 6 and 8 Alkalophiles: pH optimum between 8 and 11 Osmotic Effects on Microbial Growth Water availability is expressed as water activity (aw) (see Table 5.3). Solute...
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