2. Bacterial Physiology

2. Bacterial Physiology

Environmental factors affecting growth of bacteria  1.

Nutrients  2. Temperature  3. hydrogen ion concentration ( pH )  4. Oxygen Requirements: 氧气、二氧化 碳  5. Osmotic pressure 渗透压

Nutrient requirements of bacterial growth:  1.

Water  2. Carbon source  3. Nitrogen source 氮源  4. Minerals 无机盐  5. Growth factors 生长因子： that a cell must have for growth but cannot synthesize itself. Such as amino acids, purines 嘌呤 , pyrimidines 嘧啶 , and vitamins

Bacterial Nutrition and Growth  Classification

based on their source of

carbon Autotrophs 自养菌  2. Heterotrophs 异养菌 :saprophytes 腐生菌 ; parasites 寄生菌  1.

Bacterial growth: temperature and pH  Psychrophiles-<20(L.monocytogenes)  Mesophiles-

20-45(medically important)  Thermophiles ->45  Pathogenic

bacteria prefer an alkaline pH (7.2-7.6)

-- lactobacillus acidophilus(pH 4.0) --vibrio cholerae (pH 8.5)

Bacterial growth: atmospheric conditions  Carbon

dioxide

--may have to be supplemented

 Oxygen --obligate aerobe –absolute requirement for O2 --microaerophilic –optimal growth at low pO2 --obligate anaerobes –absence of free O2 --facultative anaerobes –either presence or absence of O2

Bacterial Growth  Bacteria

裂

multiply by binary fission 二分

time ： the time it takes for a population of bacteria to double in number

 Generation

common bacteria ： 20~60 min  most common pathogens in the body ： 5-10 hours  many

Population dynamics 群体动力 学 --the growth curve 生长曲线 The Lag Phase 迟缓期 (A)  b. The Exponential Phase 指数期 (C)  c. The Maximum Stationary Phase 稳定 期 (E)  d. The Death or decline Phase 衰亡期 (F)  a.

Artificial Cultivation of Bacteria 细菌的人工培养 

The biochemical (nutritional) environment is made available as a culture medium

Classification according to physical condition: ． liquid medium  b ． solid medium  C ． semisolid medium a

Bacterial growth: solid media  Bacteria

grow on solid media form colonies,which originate from a single bacterial cell

 On

plate

Classification according to basic ingredients Minimal essential growth medium 基础 培养基  b. Enrichment medium 增菌培养基  c. Selective medium 选择培养基  d. Differential medium 鉴别培养基  a.

designated by a Latin binominal （拉丁双名法）  前属名，后种名  Staphylococcus

(genus) aureus (species)