Chapter 6,part A Microbial Growth
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings B.E Pruitt & Jane J. Stein Chapter 6, part A Microbial Growth
Microbial Growth o Microbial growth increase in number of cells, not cell size
Microbial Growth • Microbial growth = increase in number of cells, not cell size
The Requirements for Growth:Physical Requirements 。Temperature Minimum growth temperature Optimum growth temperature Maximum growth temperature
• Temperature • Minimum growth temperature • Optimum growth temperature • Maximum growth temperature The Requirements for Growth: Physical Requirements
Temperature Thermophiles Hyperthermophiles Mesophiles Psychrotrophs Psychrophiles -10 0 10 20 30 4050 60 70 80 90 100 110 Temperature (C) Figure 6.1
Temperature Figure 6.1
Psychrotrophs 。Grow between0°Cand20-30°C 。Cause food spoilage
• Grow between 0°C and 20-30°C • Cause food spoilage Psychrotrophs
Psychrotrophs 130 260 120 240 1 10 Temperatures in this range destroy most microbes, although lower temperatures take more time. 2 00 160 70 140 60 Very slow bacterial growth 120 50 40 Danger zone Rapid growth of bacteria;some may produce toxins. 80 20 10 Many bacteria survive;some may grow. 40 Refrigerator temperatures;may allow slow growth of spoilage bacteria,very few pathogens. -10 No significant growth below freezing. -20 -30 Figure 6.2
Psychrotrophs Figure 6.2
The Requirements for Growth:Physical Requirements 。pH Most bacteria grow between pH 6.5 and 7.5 Molds and yeasts grow between pH 5 and 6 Acidophiles grow in acidic environments
• pH • Most bacteria grow between pH 6.5 and 7.5 • Molds and yeasts grow between pH 5 and 6 • Acidophiles grow in acidic environments The Requirements for Growth: Physical Requirements
The Requirements for Growth:Physical Requirements Osmotic Pressure Hypertonic environments,increase salt or sugar, cause plasmolysis Extreme or obligate halophiles require high osmotic pressure Facultative halophiles tolerate high osmotic pressure
The Requirements for Growth: Physical Requirements • Osmotic Pressure • Hypertonic environments, increase salt or sugar, cause plasmolysis • Extreme or obligate halophiles require high osmotic pressure • Facultative halophiles tolerate high osmotic pressure
The Requirements for Growth:Physical Requirements Plasma Plasma membrane Cell wall membrane H2O NaCl 0.85% NaCI 10% Figure 6.4
The Requirements for Growth: Physical Requirements Figure 6.4
The Requirements for Growth:Chemical Requirements 。Carbon Structural organic molecules,energy source Chemoheterotrophs use organic carbon sources ·Autotrophs use CO2
• Carbon • Structural organic molecules, energy source • Chemoheterotrophs use organic carbon sources • Autotrophs use CO2 The Requirements for Growth: Chemical Requirements