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Bacterial Physiology

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					    Chapter2
Bacterial Physiology
             outline
I. Physical and Chemical Properties
II. Growth and Proliferation
III.Metabolism
IV. Cultivation Method
V. Classification and Nomenclature
I Physical and Chemical Properties

i. Chemical composition
  Water, inorganic salts, proteins, carbohydrates,
     lipids, nucleic acids
Macronutrients(macroelements)
  Carbon, oxygen, hydrogen, nitrogen, sulfur,
     phosphorus and other metal ions (potassium,
     calcium, magnesium and iron)
  The first six(C, O, H, N, S, and P) are
     components of carbohydrates, lipids,
     proteins, and nucleic acids.
Micronutrients(trace elements)
ii. Physical properties
 –   Optical property
 –   Surface area
 –   Charged phenomena
 –   Semi-permeability
 –   Osmotic pressure
 II Growth and Proliferation
i. Bacterial requirements for growth
 –   Nutrients
 –   pH
 –   Temperature
 –   Oxygen
 –   Osmotic pressure
      (Optimal environmental condition)
         Nutrients
Nutrient Requirements
 – Carbon sources
 – Nitrogen sources
 – Inorganic salts and trace elements
 – Growth factors
 – Water
Nutritional types of bacteria

• Autotroph
 reduced inorganic molecules
• Heterotroph
 organic molecules
 – saprophyte
 – parasite
Uptake of nutrients by bacteria

 o Passive diffusion
    simple diffusion
    Facilitated diffusion
 o Active transport
                  pH
• Many bacteria grow best at neutral pH.
  (pH 7.2-7.6)
• Some specialized bacteria can survive
  and even grow in acid or alkaline
  conditions.
  – T.B.          pH 6.5-6.8
  – V. cholerae   pH 8.4-9.2
Temperature




Temperature and Growth
                 Optimal T
Psychrophiles    10-20 C
Mesophiles       20-40 C
Thermophiles     56-60 C

Heat-shock proteins, Hsp
Temperature ranges for microbial growth
    Oxygen Requirements
•       Obligate aerobes
    –    Must grow in the presence of air
    –    They can not carry out fermentation
•       Microaerophilic bacterium
    –    Grow well in low concentrations of oxygen
    –    Killed by higher concentrations of oxygen
•       Facultative anaerobe
    –    Perform both fermentation and aerobic
         respiration
    –    Can survive in the presence of oxygen
•       Obligate anaerobe
• Obligate anaerobes
 – Do not carry out oxidative phosphorylation
 – Killed by air
 – Lack certain enzymes
   cytochrome and cytochrome oxidace
   superoxide dismutase (SOD)
          O2- + 2H+ to H2O2
   catalase
          2H2O2 to 2H2O + O2
   peroxidase
          H2O2 to H2O using NAD to NADH
  ii. Growth and multiplication
         mode: Binary fission




Generation time:
the time required for bacterial mass to double.
  20-30min, T.B. 18-20h
The growth curve
 Phases of Microbial Death Curve

Section
  of           Phase    Growth rate
 curve
   A    Lag            Zero
  B    Log             Constant
  C    stationary      Decreasing
  D    Death           Negative(death)
CO2

Osmotic pressure
     III Metabolism
i. Energy metabolism of bacteria
 – Catabolism
 – anabolism

 – Respiration
 – Fermentation
ii. Metabolic products of bacteria
  1. Catabolism and biochemical reaction
    •   Sugar fermentation
    • IMViC
         Indole
         Methyl red
         VP
         Citrate utilization
    •   H2S
    •   Urease
2. Anabolic products of bacteria
  – Pyrogen
  – Toxin and invasive enzyme
    (endotoxin, exotoxin)
  – Pigment
  – Antibiotics
  – Bacteriocin
  – Vitamins
      IV Cultivation Method
i. Environmental factors affecting growth
  Nutrients; pH; Temperature; Aeration ; Ionic
     strength; Osmotic pressure
   Basic medium
     0.3% 牛肉膏
     1% 蛋白胨           Liquid medium
     0.5% NaCl
     (1-2% agar)     Solid medium
     (0.3-0.5% agar) Semi-solid medium
ii. Growth of bacteria in culture
    medium
  i. Liquid medium or Broth
    1) Homogeneous turbidity
    2) Surface
    3) Bottom
  ii. Solid agar medium
    Colony and mossy
    1) Smooth colony
    2) Rough colony
    3) Mucoid colony
  iii. Semi-solid agar medium
iii. Types of Culture medium
  basic medium
  nutrient medium
  selective medium
  differential medium
  anaerobic medium
iv. Usage of bacterial culture
  i. Diagnosis, prevention and treatment
       of infection diseases
  ii. Characterization of bacteria
  iii. Preparation of vaccines, toxoids and
       other biologic prducts
  iv. Application in industry and
       agriculture
  v. Uses for genetic engineering
V Classification and nomenclature

       Taxonomic ranks
  Formal rank         Example
    Kingdom         Prokaryotae
    Division       Gracillicutes
      Class       Scotobacteria
     Order         Eubacteriales
     Family     Enterobacteriaceae
     Genus         Escherichia
    Species           Coli
Family:a group of related genera.
Genus:group of related species.
Species: a group of related strains.
Type: sets of strain within a species
   – serotype
   – Phage-type
   – biotype
   – genotype
Strain: one line or a single isolate of a
  particular species.
Bionomial Nomenclature:
genus+species

Genus Species        种名    属名
S.    aureus         金黄色   葡萄球菌
N.    meningitides   脑膜炎   奈瑟菌
E.    coli           大肠    埃希菌
          Chapter3
Disinfection and sterilization
    outline
   Definition
Physical methods
Chemical methods
            I Definition

•   Disinfection
•   Sterilization
•   Antisepsis
•   Asepsis, asepsis technique
i. Disinfection
 – killing, or removal of
   microorganisms that may cause
   disease.
 – primary goal is to destroy
   potential pathogens.
ii. Sterilization
  – all living cells, viable spores,
    viruses, and viroids are either
    destroyed or removed from an
    object or habitat.

  – totally free of viable
    microorganisms, spores, and
    other infectious agents.
iii.Antisepsis
  – prevention of sepsis and is
    accomplished with antiseptics.


iv. Asepsis
  – without living microorganisms
Methods for control of
   microorganisms
Physical methods
      Heat    Hot-air sterilizer
              Autoclaving
      Radiation
      Filtration
      Ultrasound
      Dryness
      Low temperature
Chemical agents
      II physical methods
i. Heat
 1. Dry heat
   Incineration
   Direct flames
   Hot-air sterilizer
      –   160-170C for 2 hours----spores
      –   Glass petri dishes and pipettes
   Infrared
   microwave
2. Moist heat
 Pasteuriztion
   •   63C for 30min
   •   Flash pasteuriztion - 72C for 15s
   •   Ultrahigh-temperature(UHT)
       sterilization-140 to 150C for 1 to 3s
 Boiling
 Free-flowing steam disinfection
 Autoclaving
   •   15 pounds(1.05kg/cm2), 121C for 15-
       20min
ii. Radiation
  Ultraviolet, UV
    •   250-260nm
    •   Quite lethal but does not penetrate glass, dirt
        films, water, and other substances very
        effectively.
    •   To sterilize the air and any exposed surfaces
    •   Can burn the skin and damage eyes
  Ionizing radiation
    •   An excellent sterilizing agent and penetrates
        deep into objects
    •   Cobalt 60 source
iii. Filtration
  •   Rather than directly destroying
      contaminating microorganisms, the filter
      simply removes them.
  •   Membrane filter
iv. Ultrasound
v. Dryness
vi. Low temperatures
  III The Use of Chemical
      Agents in Control
• Chemical agents
  –   Phenolics 酚
  –   Alcohols 醇
  –   Heavy metals 重金属
  –   Halogens 卤素
  –   Detergents 去污剂
  –   Aldehydes 醛
• Factors affecting the results
  – Nature, concentration and acting time
    of the disinfectant
  – Type and amount of the microbe
  – Temperature
  – pH
  – Organic matter