Chapter2Chapter2 Bacterial Physiology Bacterial Physiology

Xin GangDepartment of microbiology and immunolog

y Shantou University medical college

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I. Physical and Chemical Properties

II. Growth and ProliferationIII. MetabolismIV. Cultivation MethodV. Classification and

Nomenclature

I Physical and Chemical I Physical and Chemical PropertiesProperties

i. Chemical compositionWater, inorganic salts, proteins, carbohydrates,

lipids, nucleic acidsMacronutrients(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 II Growth and ProliferationProliferation

i.i. Bacterial requirements for Bacterial requirements for growthgrowth

– Nutrients– pH– Temperature– Oxygen– Osmotic pressure (Optimal environmental condition)

Nutrients Nutrients Nutrient Requirements

– Carbon sources– Nitrogen sources– Inorganic salts and trace

elements– Growth factors– Water

Nutritional types of bacteria

•Autotrophreduced inorganic molecules

•Heterotrophorganic molecules–saprophyte–parasite

Uptake of nutrients by bacteria

o Passive diffusionsimple diffusionFacilitated diffusion

o Active transport

pHpH• Many bacteria grow best at neutral pH.

(pH 7.2-7.6)• Some specialized bacteria can survive a

nd even grow in acid or alkaline conditions.– T.B. pH 6.5-6.8– V. cholerae pH 8.4-9.2

Temperature and Growth

Temperature Temperature

Optimal T

Psychrophiles 10-20 CMesophiles 20-40 CThermophiles 56-60 C

Heat-shock proteins, Hsp

Temperature ranges for microbial growth

Oxygen Oxygen RequirementsRequirements

• 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 res

piration– 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 oxidacesuperoxide dismutase (SOD) O2

- + 2H+ to H2O2 catalase

2H2O2 to 2H2O + O2peroxidase

H2O2 to H2O using NAD to NADH

ii. Growth and multiplication

Generation time:Generation time:the time required for bacterial mass to double.

20-30min, T.B. 18-20h

mode: Binary fissionmode: Binary fission

TheThe growth curve growth curve

Phases of Microbial Death Phases of Microbial Death CurveCurve

Section of

curvePhase Growth rate

A Lag Zero

B Log Constant

C stationary Decreasing

D Death Negative(death)

CO2CO2

Osmotic pressureOsmotic pressure

III MetabolismIII Metabolism

i. Energy metabolism of bacteria

– Catabolism– anabolism

– Respiration– Fermentation

ii. Metabolic products of bacteria1. Catabolism and biochemical reaction

• Sugar fermentationSugar fermentation• IMViC

Indole Methyl red

VP Citrate utilization

• H2S• Urease

2. Anabolic products of bacteria– PyrogenPyrogen– Toxin and invasive enzyme

(endotoxin, exotoxin)– Pigment– Antibiotics– Bacteriocin– Vitamins

IV Cultivation MethodIV Cultivation Method

i. Environmental factors affecting growthNutrients; pH; Temperature; Aeration ; Ionic st

rength; Osmotic pressureBasic medium

0.3% 牛肉膏1% 蛋白胨0.5% NaCl

Liquid medium

(1-2% agar) Solid medium(0.3-0.5% agar) Semi-solid medium

ii. Growth of bacteria in culture medium

i. Liquid medium or Broth1) Homogeneous turbidity2) Surface3) Bottom

ii. Solid agar mediumColony and mossy1) Smooth colony2) Rough colony3) Mucoid colony

iii.Semi-solid agar medium

iii.Types of Culture mediumbasic medium

nutrient mediumselective mediumdifferential mediumanaerobic medium

iv. Usage of bacterial culturei. Diagnosis, prevention and treatment

of infection diseasesii. Characterization of bacteriaiii. Preparation of vaccines, toxoids and

other biologic prductsiv. Application in industry and agricultu

rev. Uses for genetic engineering

V Classification and V Classification and nomenclaturenomenclatureTaxonomic Taxonomic

ranksranksFormal rank Example

Kingdom ProkaryotaeDivision Gracillicutes

Class ScotobacteriaOrder EubacterialesFamily EnterobacteriaceaeGenus 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 Chapter3 Disinfection and sterilizationDisinfection and sterilization

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Definition Physical methodsChemical methods

• Disinfection• Sterilization• Antisepsis• Asepsis, asepsis technique

I Definition I Definition

i. Disinfection– killing, or removal of microorga

nisms that may cause disease.– primary goal is to destroy pote

ntial pathogens.

ii. Sterilization– all living cells, viable spores, vir

uses, 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 Methods for control of microorganismsmicroorganisms

Physical methods Heat Hot-air sterilizerHot-air sterilizer Autoclaving Autoclaving

Radiation Filtration Ultrasound Dryness Low temperature

Chemical agents

II physical methodsII physical methods

i. Heat1. Dry heat

IncinerationDirect flamesHot-air sterilizer

– 160-170C for 2 hours----spores– Glass petri dishes and pipettes

Infraredmicrowave

2. Moist heatPasteuriztion

• 63C for 30min• Flash pasteuriztion - 72C for 15s• Ultrahigh-temperature(UHT) sterilizati

on-140 to 150C for 1 to 3sBoilingFree-flowing steam disinfectionAutoclaving

• 15 pounds(1.05kg/cm2), 121C for 15-20min

ii. RadiationUltraviolet, 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 filterMembrane filter

iv.Ultrasoundv. Drynessvi.Low temperatures

III The Use of Chemical III The Use of Chemical Agents in ControlAgents 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