3 Physiology of Bacteria Xiao-Kui Guo PhD firstname.lastname@example.org http://www.microbiology.org.cn
Content: • Growth and nutrition • Growth requirement • Bacterial metabolism • Cultivation of bacteria • Classification of bacteria
Growth and nutrition I: • According to the different carbon source, the bacteria can be divided in to class: • Autotrophs: creature consume inorganic carbon for growth • Heterotrophs: creature consume organic carbon for growth Hunting or dying, this is a question! I can live happily if only the light and CO2 exist.
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: 20-60mins • Average time in vivo: 5-10hours
Growth and nutrition IV:Bacteria growth curve in liquid 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. Exponential phase: when the bacteria are adapt to the new condition, the number will grow at an incredible rate. 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. Lag phase: bacteria take time to get accustomed to the new living condition.
Growth requirement I:Hydrogen ion concentration (pH) • Most bacteria have a narrow optimal pH range: • Neutralophiles: pH 6.0~8.0 • Acidophiles: pH < 5.5 • Alkaliphiles: pH > 8.5 • The pH range of most pathogen is 7.2~7.6 but with some exceptions. • V. cholerae pH 8.4~9.2 • M. 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 aerobes • Microaerophilic bacterium • Facultative anaerobes • Obligate 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 Poison for anerobes . O2- + H2O2 O2 + OH- + OH Fe3+ /Fe2+ The aerobes process superoxide dismutase and catalase to reduce the poison The lacking of the enzyme makes the anerobes have no ability to reduce the toxin. SOD 2O2- + 2H+ O2 + H2O2 2H2O2 2H2O + O2 Catalase
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 test Voges-Proskauer (VP) test Methyl red (MR) test Citrate test The test based on the products of the sugar Indole test H2S test The test based on the products of the protein Urealytic test The test based on the other products
Bacteria metabolism III:IMViC test • The IMViC test can be used to distinguish different category of intestinal bacilli. I M Vi C Indole test Methyl red (MR) test VP test Citrate 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 • Pigment • Antibody • Bacteriocin • 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 more aggressive
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 medium Enrichment medium Selective medium Differential medium Anaerobic medium Classified by Physical condition Liquid medium Solid 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 solid medium: for the selection and purification of the bacteria The liquid medium: for the enrichment of the bacteria
The classification of bacteria I: Kingdom phylum class order Genus Family 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.
The classification of bacteria II:Naming • In English: the Latin binominal Staphylococcus aureus Generic name Specific name • In Chinese 金黄色 葡萄球菌 属名 种名
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