Lecture 6 6. 8 Effect of environment on growth 6. 9 Microbial growth at cold Temperatures 6.10 Microbial Growth at High Temperatures 6. 11 Microbial Growth at Low or High pH 6.12 Osmotic Effects on microbial growth 6. 13 Oxygen and microbial Growth
Lecture 6 • 6.8 Effect of Environment on Growth • 6.9 Microbial Growth at Cold Temperatures • 6.10 Microbial Growth at High Temperatures • 6.11 Microbial Growth at Low or High pH • 6.12 Osmotic Effects on Microbial Growth • 6.13 Oxygen and Microbial Growth
Effect of Temperature on Growth Rate Enzymatic reactions occurring at maximal possible rate g Enzymatic reactions Optimum occurring at increasingly rapid rates Minimum Maximum Temperature Membrane gelling; Protein denaturation; transport processes collapse of the cytoplasmic so slow that growth membrane; thermal cannot occur lysis
Effect of Temperature on Growth Rate
Variations in Temperature Optima Thermophile Example Hyperthermophile hyperthermophile Bacillus stearothermophilus Example Example: Mesophile Thermococcus celer Pyrolobus fumarii Example Escherichia coli Psychrophile Polaromonas vacuolate 10 70 110 120 Temperature(C)
Variations in Temperature Optima
Psychrophiles Optimun15° C or lower · Maximun<20° Minimun<0° Many are very sensitive to moderate temperatures Enzyme denaturation at moderate temp Greater proportion of unsaturated fatty acids in membrane phospholipids Ocean depths: constant temp <5C
Psychrophiles • Optimum 15°C or lower • Maximum <20° • Minimum 0° • Many are very sensitive to moderate temperatures • Enzyme denaturation at moderate temp • Greater proportion of unsaturated fatty acids in membrane phospholipids • Ocean depths: constant temp <5oC
Psychrotolerant · Grow at0° Optimun20-40° Mesophiles capable of growth at low temperatures found in temperate climates
Psychrotolerant • Grow at 0° • Optimum 20-40° • Mesophiles capable of growth at low temperatures • found in temperate climates