文档介绍：Chapter 3
Microbial Growth
Microbial Growth means
increase in number of cells, not cell size. It is very confusing with reproduction (繁殖) in other forms of life (e. g. animals).
Growth requirements
Physical
Chemical
1 Temperature
2 pH
3 Osmotic pressure (water)
4 Light
1 Carbon
2 Nitrogen
3 Sulfur
4 Phosphorus
5 anic element
6 Oxygen
7 growth factors
Temperature
Minimum growth temperature
Optimum growth temperature
Maximum growth temperature
Physical Requirements for Growth: 1 temperature
专性嗜冷
兼性嗜冷
中温型
嗜热
极端嗜热
Arctic/antarctic
Sea/refrige
mammal/soils
compost
Spring/sea volcano
Question:
Is it always safe if foods are stored in refrigerator for long time?
Figure
pH
Most bacteria grow between pH and
Molds and yeasts grow between pH 5 and 6
Acidophiles grow in acidic environments
Physical Requirements for Growth: 2 pH
Physical Requirements for Growth: 3 osmotic pressure
Osmotic Pressure (=water availability)
Hypertonic (高渗) environments, increase salt or sugar, cause plasmolysis(质壁分离)
Extreme or obligate (专性) halophiles require high osmotic pressure
Facultative (兼性) halophiles tolerate high osmotic pressure
Plasmolysis
Figure
Cell in normal osmotic pressure environment
Cell in hypertonic environment