Chapter2 Bacterial Physiology

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Chapter2 Bacterial Physiology

• Xin Gang
• Department of microbiology and immunology Shantou
  University medical college

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outline

1. Physical and Chemical Properties
2. Growth and Proliferation
3. Metabolism
4. Cultivation Method
5. Classification and Nomenclature

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I Physical and Chemical Properties

• 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)

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• Physical properties
• Optical property
• Surface area
• Charged phenomena
• Semi-permeability
• Osmotic pressure

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II Growth and Proliferation

• Bacterial requirements for growth
• Nutrients
• pH
• Temperature
• Oxygen
• Osmotic pressure
• (Optimal environmental condition)

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Nutrients

• Nutrient Requirements
• Carbon sources
• Nitrogen sources
• Inorganic salts and trace elements
• Growth factors
• Water

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• Nutritional types of bacteria
• Autotroph
• reduced inorganic molecules
• Heterotroph
• organic molecules
• saprophyte
• parasite

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• Uptake of nutrients by bacteria
• Passive diffusion
• simple diffusion
• Facilitated diffusion
• Active transport

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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

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Temperature
Temperature and Growth
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Optimal T
Psychrophiles 10-20 ?C
Mesophiles 20-40 ?C
Thermophiles 56-60 ?C
Heat-shock proteins, Hsp
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Temperature ranges for microbial growth
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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

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• 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

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1. Growth and multiplication

mode Binary fission
Generation time the time required for bacterial
mass to double. 20-30min, T.B. 18-20h
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The growth curve
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Phases of Microbial Death Curve
Section of curve Phase Growth rate
A Lag Zero
B Log Constant
C stationary Decreasing
D Death Negative(death)
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• CO2
• Osmotic pressure

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III Metabolism

• Energy metabolism of bacteria
• Catabolism
• anabolism
• Respiration
• Fermentation

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• Metabolic products of bacteria
• Catabolism and biochemical reaction
• Sugar fermentation
• IMViC
• Indole
• Methyl red
• VP
• Citrate utilization
• H2S
• Urease

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• Anabolic products of bacteria
• Pyrogen
• Toxin and invasive enzyme
• (endotoxin, exotoxin)
• Pigment
• Antibiotics
• Bacteriocin
• Vitamins

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IV Cultivation Method

• Environmental factors affecting growth
• Nutrients pH Temperature Aeration Ionic
  strength Osmotic pressure
• Basic medium
• 0.3 ???
• 1 ???
• 0.5 NaCl

Liquid medium
(1-2 agar) Solid medium (0.3-0.5 agar)
Semi-solid medium
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• Growth of bacteria in culture medium
• Liquid medium or Broth
• Homogeneous turbidity
• Surface
• Bottom
• Solid agar medium
• Colony and mossy
• Smooth colony
• Rough colony
• Mucoid colony
• Semi-solid agar medium

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• Types of Culture medium
• basic medium
• nutrient medium
• selective medium
• differential medium
• anaerobic medium

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• Usage of bacterial culture
• Diagnosis, prevention and treatment of infection
  diseases
• Characterization of bacteria
• Preparation of vaccines, toxoids and other
  biologic prducts
• Application in industry and agriculture
• Uses for genetic engineering

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V Classification and nomenclature
Taxonomic ranks
Formal rank Example
Kingdom Prokaryotae
Division Gracillicutes
Class Scotobacteria
Order Eubacteriales
Family Enterobacteriaceae
Genus Escherichia
Species Coli
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• Familya group of related genera.
• Genusgroup 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.

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• Bionomial Nomenclature
• genusspecies

Genus Species ?? ??
S. aureus ??? ????
N. meningitides ??? ???
E. coli ?? ???
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Chapter3 Disinfection and sterilization
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outline

• Definition
• Physical methods
• Chemical methods

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I Definition

• Disinfection
• Sterilization
• Antisepsis
• Asepsis, asepsis technique

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• Disinfection
• killing, or removal of microorganisms that may
  cause disease.
• primary goal is to destroy potential pathogens.

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• 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.

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• Antisepsis
• prevention of sepsis and is accomplished with
  antiseptics.
• Asepsis
• without living microorganisms

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Methods for control of microorganisms

• Physical methods
• Heat Hot-air sterilizer
• Autoclaving
• Radiation
• Filtration
• Ultrasound
• Dryness
• Low temperature
• Chemical agents

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II physical methods

• Heat
• Dry heat
• Incineration
• Direct flames
• Hot-air sterilizer
• 160-170?C for 2 hours----spores
• Glass petri dishes and pipettes
• Infrared
• microwave

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• 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

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• 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

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• Filtration
• Rather than directly destroying contaminating
  microorganisms, the filter simply removes them.
• Membrane filter

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1. Ultrasound
2. Dryness
3. Low temperatures

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III The Use of Chemical Agents in Control

• Chemical agents
• Phenolics ?
• Alcohols ?
• Heavy metals ???
• Halogens ??
• Detergents ???
• Aldehydes ?

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• Factors affecting the results
• Nature, concentration and acting time of the
  disinfectant
• Type and amount of the microbe
• Temperature
• pH
• Organic matter