微生物学课件

Measuring viable bacteria
测量活菌数
• Colony forming units 菌落形成单位
colony
Membrane filtration procedure
Colonies on membrane filters
standard medium
fecal coliform medium (blue colonies)
Measurement: Growth & Reproduction
微生物生长和繁殖的测定
Growth measurement 生长测定
1. Direct method 直接法
– Dry weight: ≈ 10~20% of wet weight – E. Coli: 2.8×10-13 g /cell
• Colony growth
= individual growth + individual reproduction 群体生长 = 个体生长 + 个体繁殖
• Microbial growth usually refers to colony growth 微生物生长通常指细胞数量的增加
Content
1. On plate: for aerobic & anaerobic cells
• Colony forming unit, cfu 菌落形成单位
1. Pour plate 浇注平板 2. Spread plate 涂布平板
2. For anaerobic cells 厌氧菌菌落记数法
• • Hungate roll-tube technique亨盖特滚管培养法 Semi-solid agar method: anaerobic environment
1. Lag phase 延滞期 2. Log phase 快速生长期 3. Decline phase 生长衰退期
.
1. Lag Phase 延迟期
• • • • Bacteria are “checking out” their surroundings Cells are very active metabolically # of cells changes very little 1 hour to several days
1. Measurement of bacterial growth 2. Characteristics of microbial growth
– Typical growth curve
3. 4. 5.
Types of microbial culture Factors influencing the bacterial growth The control of harmful microbial growth
2. Log Phase 对数期
• Rapid cell growth (exponential growth) by binary fission 二分分裂 with highest R • Population doubles every generation • Active metabolism & sensitive to adverse conditions
1. 2. 3. • Induced germination Controlled darkness Heat shock Filtration (by size), centrifugation, etc
2. Screen mechanically
The synchronous growth of a bacterial population
•
By careful selection of cells that have just divided, a bacterial population can be synchronized in the bacterial cell division cycle. Synchrony can be maintained for only a few generations
Study Microbial Growth
• Study tissue section of ultra thin under EM 电镜下细胞组织超薄切片
– Single cell
• Study biochemical reaction of synchronous culture 同步培养群体的生化特性
G times for some common bacteria
Bacterium
Escherichia coli 大肠杆菌 Bacillus megaterium Streptococcus lactis 乳糖链球菌 Streptococcus lactis 乳糖链球菌 Rhizobium japonicum 根瘤菌
Measure bacterial mass (live + dead) in liquid culture
测量液体培养物中细菌总量（死菌＋活菌） • Turbidity 浊度 (Cloudiness)
– Abs595, Abs610
Reproduction Measurement 繁殖测定
• Only effective to: bacteria & yeast in single-cell state, not to filamentous actinomycetes & mould 仅适合于单细胞状态的细菌和酵母，而 在丝状的放线菌和霉菌中不适用
Growth of Organism
• Many bacteria: under optimal conditions
– can divide every 20 to 30 minutes.
• Human:
– generation time: ~25 years.
• All forms of life:
m-Endo agar for detecting E. coli
Wort agar for yeast and molds
Some Methods used to measure bacterial growth
Method
Direct microscopic count Viable cell count (colony counts) Turbidity measurement Measurement of total N or protein Measurement of Biochemical activity e.g. O2 uptake, CO2 & ATP production, etc. Measurement of dry/wet weight of cells or volume of cells after centrifugation
1. Direct method 2. Indirect method
Direct method
• Counting cell number：
– Direct under microscopic 光镜下记数板记数
• Total cell number 总菌数: • Viable number 活菌数: differentiate dying method
– antibiotics – anti-microbial agents
Important Parameters in Log Phase 对数期重要参数
• Growth rate (R) 生长速率常数 • Generation time (G) 增代时间: time required for a cell to divide
Factors Influencing the Length of Lag Phase
1. Bacteria strain 菌种 2. The colony age of inoculum 接种龄
– Inoculum of log phase: shorten lag phase
3. Amount of inoculum 接种量
Bacterial colonies growing on a plate of nutrient agar
Microbial Growth and Its Control
第六章 微生物的生长及其控制
Microbial Growth
微生物的生长
Microbial Growth - refers to the # of cells, not the size of the cells
– Most about 1 ~ 3 hrs.
• E. coli - 20 minutes • Mycobacterium tuberculosis 结核分支杆菌- 24 Hrs.
– Doubling time 倍增时间 of cytoplasma
• Reproduction times (n) 繁殖代数: x2 = x1 * 2n
– Capable: exponential/logarithmic growth指数生长 – Numbers double each generation (e.g. 1, 2, 4, 8…)
Typical Bacterial Exponential Growth Curve
•2-5x109 cells/ml, 12-18 hours. •rich culture medium, aerobic •human growth curve: looks the same
– “average value” – Synchronous growth 同步生长
Synchronous growth 同步生长