《微生物学》课程教学课件（PPT讲稿）Chapter 9 Microbial taxonomy

Chapter9 Microbial taxonomy Three separate but interrelated parts 1. Classification: the arrangement of organisms into groups or taxa based on mutual similarity or evolutionary relatedness 2. Nomenclature: the branch of taxonomy concerned with the assignment of names to taxonomic groups in agreement with published rules 3. Identification: the practical side of taxonomy, the process of determining that a particular isolate belongs to a recognized taxon

Three separate but interrelated parts: 1. Classification: the arrangement of organisms into groups or taxa based on mutual similarity or evolutionary relatedness. 2. Nomenclature: the branch of taxonomy concerned with the assignment of names to taxonomic groups in agreement with published rules. 3. Identification: the practical side of taxonomy, the process of determining that a particular isolate belongs to a recognized taxon. Chapter9 Microbial taxonomy

Taxonomy is important for several reasons 1. It allows us to organize huge amounts of knowledge about organisms Allows us to make predictions and frame hypotheses for further research based on knowledge of similar organisms It places microorganisms in meaningful, useful groups with precise names so that microbiologists can work with them and communicate efficientl 4. Identification of microorganisms accurately

Taxonomy is important for several reasons 1. It allows us to organize huge amounts of knowledge about organisms 2. Allows us to make predictions and frame hypotheses for further research based on knowledge of similar organisms. 3. It places microorganisms in meaningful, useful groups with precise names so that microbiologists can work with them and communicate efficiently. 4. Identification of microorganisms accurately

y Strain: onesingleisolateorline Type: sub-setofspecies /⑤明明同加(si3 y Genus: related species Famiy: relatedgenera Order class, phylum domain

Taxomomic ranks ✓ Strain: one single isolate or line ✓ Type: sub-set of species ✓ Species: related strains ✓ Genus: related species ✓ Family: related genera ✓ Order; class; phylum; domain

Related concepts aH a collection of strains that have a similar G+C composotion and 70% or greater similarity as judged by DNA hybridization experiments o variant procaryotic strains characterized Dy biochemical or physiological differences roars differ morphologically eroa have distinctive antigenIc properties nesta it is usually one of the first strains studied and often is more fully characterized than other strains

Related concepts A species: a collection of strains that have a similar G+C composotion and 70% or greater similarity as judged by DNA hybridization experiments. A biovars: variant procaryotic strains characterized by biochemical or physiological differences. Morphovars: differ morphologically Serovars: have distinctive antigenic properties Type strain: it is usually one of the first strains studied and often is more fully characterized than other strains

Classification systems Phenetic classification: one that groups organisms together based on the mutual similarity of their phenotypic characteristics Comparing as many attributes as possible umerical taxonomy: computers may be used to analyze data for the production of phenetic classification Information about the properties of organisms converted into a form suitable for numerical analysis and then compared by means of a computer Phylogenetic classification: based on evolutionary relationships rather than general resemblance defficult because of the lack of a good fossil record Comparision of genetic material and gene products

Classification systems Phenetic classification: one that groups organisms together based on the mutual similarity of their phenotypic characteristics. Comparing as many attributes as possible. Numerical taxonomy: computers may be used to analyze data for the production of phenetic classification. Information about the properties of organisms is converted into a form suitable for numerical analysis and then compared by means of a computer. Phylogenetic classification: based on evolutionary relationships rather than general resemblance. defficult because of the lack of a good fossil record. Comparision of genetic material and gene products

Major characteristics used in taxonomy Morphological characteristics Physiological and metabolic characteristics Ecological characteristics Genetic analysis Molecular characteristics

Major characteristics used in taxonomy Morphological characteristics Physiological and metabolic characteristics Ecological characteristics Genetic analysis Molecular characteristics

Morphological characteristics Cell shape Mechanism of motility Cell size Endospore shape and location Cilia and flagella Spore morphology and location Cellular inclusions Colonial morphology Color Ultrastructural characteristics Staining behavior

Morphological characteristics Cell shape Cell size Cilia and flagella Cellular inclusions Color Mechanism of motility Endospore shape and location Spore morphology and location Colonial morphology Ultrastructural characteristics Staining behavior

Physiological, metabolic and Ecological characteristics o General nutritional type o Carbon and nitrogen o Growth temperature sources optimum and range n Cell wall o Mechanisms of energy constituents conversion 口 Energy sources n pH optimum and growth o Fermentation range products o Photosynthetic pigments o Luminescence o Salt requirements and n Motility tolerance o Osmotic tolerance o Secondary metabolites formed o Storage inclusions n Sensitivity to metabolic inhibitors and antibiotics

Physiological, metabolic and Ecological characteristics Carbon and nitrogen sources Cell wall constituents Energy sources Fermentation products Luminescence Motility Osmotic tolerance Storage inclusions General nutritional type Growth temperature optimum and range Mechanisms of energy conversion pH optimum and growth range Photosynthetic pigments Salt requirements and tolerance Secondary metabolites formed Sensitivity to metabolic inhibitors and antibiotics

Genetic analysis The study of transformation and conjugation in bacteria is sometimes taxonomically useful Plasmid-borne traits can cause errors in bacterial taxonomy if care is not taken Transformation can occur between different procaryotic species but only rarely between genera E coli can undergo conjugation with the genera Salmonella and shigella but not with Proteus and enterobacter

Genetic analysis The study of transformation and conjugation in bacteria is sometimes taxonomically useful. Plasmid-borne traits can cause errors in bacterial taxonomy if care is not taken. Transformation can occur between different procaryotic species but only rarely between genera. E.coli can undergo conjugation with the genera Salmonella and Shigella but not with Proteus and Enterobacter

Historical guanine(G)+ cytosine(C (%GC) Hybridization Gene characterization sequencing other

Molecular analysis Historical • guanine (G)+ cytosine (C) (% GC) Now • Hybridization • Gene characterization – sequencing – other