3 Physiology of Bacteria

3 Physiology of Bacteria

Xiao-Kui Guo [email protected]

http://www.microbiology.org.cn

Content:

Growth and nutrition Growth requirement Bacterial metabolism Cultivation of bacteria Classification of bacteria

Section AGrowth and Nutrition

Growth and nutrition I: According to the different carbon source, the bacteri

a can be divided in to class: Autotrophs: creature consume inorganic carbon for growth Heterotrophs: creature consume organic carbon for growth

I can live happily if only the light and CO2 exist.

Hunting or dying, this is a question!

Growth and nutrition II:

The nutrition on bacteria’s dinner menu:Nitrogen

Sulfur Phosphorus

Mineral

Protein and nucleic acid

Part of the enzymes and proteins

ATP; nucleic acids; coenzymes (NAD; NADP)

Playing important role in the circle of bacteria’s life

Growth and nutrition IV: The growth of bacterial cell

The bacteria reproduced by binary fission The generation time of different kinds of

bacteria varied widely:Average time in vitro: 20-60minsAverage time in vivo: 5-10hours

Growth and nutrition IV: Bacteria growth curve in liquid

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0h 4h 8h 12h 16h 20h 24h 28h 32h 36hTime

Lg

via

ble

og

an

ism

s/m

l

Lag phase: bacteria take time to get accustomed to the new living condition.

Stationary phase, because of the exhaustion of nutrient and the

accumulation of toxic product, the new-born cells and the death cells

attach a balance.

Exponential phase: when the bacteria are adapt to the new condition, the number will grow at an incredible

rate.

Decline phase: the depletion of nutrition and the high concentration of toxin make the death rate rise. Most cell die but the survivor may persist for a long time.

Section BGrowth requirements

Growth requirement I: Hydrogen ion concentration (pH)

Most bacteria have a narrow optimal pH range:Neutralophiles: pH 6.0~8.0Acidophiles: pH < 5.5Alkaliphiles: pH > 8.5

The pH range of most pathogen is 7.2~7.6 but with some exceptions. V. cholerae pH 8.4~9.2M. Tuberculosis Ph 6.5~6.8

Growth requirement II: Temperature Psychrophilic forms: 15~20℃ Mesophilic forms: 30~37 , including all human ℃

pathogens and opportunists. Thermophilic forms: 50~60℃

Growth requirement III:Aeration

According to the aeration requirement Obligate aerobesMicroaerophilic bacteriumFacultative anaerobesObligate anaerobes

Oxygen is the treasure for human and some bacteria while the poison for others.

Growth requirement III:Why the oxygen become poison? Lacking the enzyme for respiration Lacking the enzyme for reducing the by-products of aerobic

metabolism

O2- + H2O2 O2 + OH- + OH

2O2- + 2H+ O2 + H2O2

2H2O2 2H2O + O2

.Fe3+ /Fe2+

SOD

Catalase

Poison for anerobes

The aerobes process superoxide dismutase and catalase to reduc

e the poison The lacking of the enzyme makes the anerobes have n

o ability to reduce the toxin.

Section CBacteria metabolism

Bacteria metabolism I: Cellular Respiration There are two kinds of respiration in bacteria

Fermentation: A kind of energy metabolism without oxygen and producing less ATP.

Respiration : A kind of energy metabolism with oxygen and producing more ATP.

Bacteria metabolism II: Catabolic processes

The product of the catabolic processes make it possible for us to distinguish different kinds of bacteria.

Sugar fermentation testSugar fermentation testVoges-Proskauer (VP) test Voges-Proskauer (VP) test Methyl red (MR) test Methyl red (MR) testCitrate testCitrate test

Indole test Indole test H2S testH2S test

Urealytic testUrealytic test

The test based on the products of the sugarThe test based on the products of the sugar

The test based on the products of the protein The test based on the products of the protein

The test based on the other productsThe test based on the other products

Bacteria metabolism III: IMViC test

The IMViC test can be used to distinguish different category o

f intestinal bacilli.

I M Vi C

Indole test Methyl red (MR) testMethyl red (MR) test VP testVP test Citrate testCitrate test

E. coli

Enteric bacillus

++

++- -

- -

Bacteria metabolism IV: The anabolic process

The anabolic process of the bacteria include the ingredient of the structure as well as some weapon.Pyrogen Toxin and invasive enzyme PigmentAntibodyBacteriocin Vitamin

A kind of thermo-resistant toxin formed by bacteria which causes the sharp rising of temperature in

human body and only can be degenerated under extremely high

temperature and pressure.

Including exotoxin and endotoxin (LPS), which make the bacteria m

ore aggressive

Section D Cultivation of bacteria

Cultivation of bacteria I: Medium

Medium is an artificial environment for bacteria to live and enrich.

The medium can be classified on the base of ingredient or physical condition.

Classified by ingredient

Basic mediumEnrichment mediumSelective medium

Differential mediumAnaerobic medium

Classified by Physical condition

Liquid mediumSolid medium

Semi-solid medium

Cultivation of bacteria I: The bacteria grow in three kinds of medium

The semi-solid medium: the test for motility test and for short-time preserve

The liquid medium: for the enrichment

of the bacteria

The solid medium: for the selection

and purification of the bacteria

Section E The classification of bacteria

The classification of bacteria I:

Genus

Species

Subspecies: bacteria in one species but have some obviously different property is some aspects

Type: bacteria in one species but have some slightly different property is some aspects

Strain: bacteria in one species from different origins.

Kingdom phylum class order

Family

The classification of bacteria II: Naming In English: the Latin binominal

In Chinese

Staphylococcus aureus

Generic name Specific name

金黄色 葡萄球菌

种名 属名

The End

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