《微生物学》课程教学课件（PPT讲稿）Chapter4 Microbial growth

Chapter4 Microbial growth Environmental factors on growth Growth in natural environment

Chapter4 Microbial growth Environmental factors on growth Growth in natural environment

Effect ofenvironmental factors on growth Water availability, pH, temperature, oxygen concentration, pressure, radiation and a number of other environmental factors influence microbial growth Yet many microorganismS, and particularly bacteria, have managed to adapt and fourish under environmental extremes that would destroy most organisms

Water availability, pH, temperature, oxygen concentration, pressure, radiation, and a number of other environmental factors influence microbial growth. Yet many microorganisms, and particularly bacteria, have managed to adapt and flourish under environmental extremes that would destroy most organisms. Ef ect of environmental factors on growth

Effect of temperature on bacterial growth rate Effect of Temperature on the growth of E coli Bacteria grow over a Optimum temperature 30 of growth(37.C) range of temperatures; they do not reproduce below the =20 minimum growth temperature nor above the maximum growth Minimum 1.0 temperature Maximum temperature. Within the of growth 8°C temperature of growth temperature growth range 48°C there is an optimum growth 30 4050 temperature at which bacterial °F405060708090100110120 reproduction is fastest Temperature

Bacteria grow over a range of temperatures; they do not reproduce below the minimum growth temperature nor above the maximum growth temperature. Within the temperature growth range there is an optimum growth temperature at which bacterial reproduction is fastest. Effect of temperature on bacterial growth rate

Microorganisms are classified as psychrophiles, mesophiles. thermophiles, and extremethemophiles based on their optimal growth temperature. Temperature effect: Extreme 1. Psychrophile (0-20C Thermophile 2. Mesophile (45-15C 3. Thermophile (40-700C) 4. Hyperthermophile g (65-95 5. Extrem hyper- thermophile (80-120C) 01028030405060060 termperature(C)

Microorganisms are classified as psychrophiles, mesophiles. thermophiles, and extremethemophiles based on their optimal growth temperature. Temperature effect: 1. Psychrophile (0-20oC) 2. Mesophile (45-15oC) 3. Thermophile (40-70oC) 4. Hyperthermophile (65-95oC) 5. Extrem hyper￾thermophile (80-120oC)

Temperature A most important factor influencing the growth is the temperature sensitivity of enzyme catalyzed reactions High temperature 1. Denature enzymes transport carries and other proteins 2. Microbial membranes are also disrupted by temperature extremes 3. The lipid bilayer melts and disintegrates

Temperature • A most important factor influencing the growth is the temperature sensitivity of enzyme catalyzed reactions. • High temperature: 1. Denature enzymes, transport carries, and other proteins. 2. Microbial membranes are also disrupted by temperature extremes. 3. The lipid bilayer melts and disintegrates

Optimal growth temperature Mesophiles: human body temperature pathogens s opportunists pyschrophile close to freezing thermophile close to boiling

Thermophile and Biotechnology catalyzing biochemical reactions at gh of Enzymes from thermophiles are capable temperature, they are more stable DNA polymerase, Taq polymerase, has been isolated from thermophile- Thermus aquaticus, for PCR application DNA polymerase, pfu polymerase, isolated from hyperthermophile-Pyrocuccus furiosus, is more stable and useful for PCr application, it also less prone to errors Microbial process carried out at high t also eliminate or greatly reduce cooling costs

Thermophile and Biotechnology • Enzymes from thermophiles are capable of catalyzing biochemical reactions at high temperature, they are more stable; • DNA polymerase, Taq polymerase, has been isolated from thermophile-Thermus aquaticus, for PCR application; • DNA polymerase, pfu polymerase, isolated from hyperthermophile-Pyrocuccus furiosus, is more stable and useful for PCR application, it also less prone to errors; • Microbial process carried out at high T also eliminate or greatly reduce cooling costs

Molecular basis for growing at extreme temperatures Molecular adaptations of enzymes to extreme temperatures Cold-active enzymes are more flexible due to higher portion of a helix and less amount of B- sheet Heat resistant enzymes have different folding patterns because of a few different amino acids in some critical positions from their mesophile counterpart, more salt bridges and more densely packed hydrophobic interior

Molecular basis for growing at extreme temperatures • Molecular adaptations of enzymes to extreme temperatures – Cold-active enzymes are more flexible due to higher portion of a helix and less amount of b- sheet – Heat resistant enzymes have different folding patterns because of a few different amino acids in some critical positions from their mesophile counterpart, more salt bridges and more densely packed hydrophobic interior

A-helix provides flexibilit R N CH-N CH-N-H R-CH CH H O CH Hydro gen bonds between nearby amino acids

A-helix provides flexibility

B-sheet causes more rigidity R-C R-c CzO O…H=N RC-A N-Hee OrC R-C R-C R C=O c=o…H=N R R N一H…OEC R H-N cao…H-N C-RC-R C-R Hydrogen bonds oac N一Hoc between distant N一HorC amino acids

B-sheet causes more rigidity