Lecture Outline: Classification of Microorganisms

Chapter 10 Classification of Microorganisms 1 Classification of Microorganisms Why do we need to classify living things? Helps in the quick identification of microbes Identification is useful for: 1. Diagnosis 2. Treatment 3. Prevention Classification is accomplished through taxonomy 2 Classificat...

Chapter 10 Classification of Microorganisms 1 Classification of Microorganisms Why do we need to classify living things? Helps in the quick identification of microbes Identification is useful for: 1. Diagnosis 2. Treatment 3. Prevention Classification is accomplished through taxonomy 2 Classification of Microorganisms Taxonomy - science of classification Taxon/Taxa - a class, group or category of something Taxonomist - scientist who studies classification Phylogeny - shows evolutionary relationship between organisms in a group 3 The Taxonomic Hierarchy 4 Classification of Microorganisms & Taxonomy Organisms are arranged into taxa 1. What are the 2 highest (most inclusive) or least specific taxa in biology? 2. What are the 2 lowest (least inclusive) or most specific taxa in biology? Binomial Nomenclature  A two-part naming system for living organisms  Consists of Genus name, followed by species name  Example - binomial nomenclature for these orgasms:  Escherichia coli, Helicobacter pylori = bacteria  Penicillium chrysogenum = fungus (mold)  Homo sapiens = humans 5 The Three Domain System A type of biological classification system developed in 1990 What are the three Domains of living organisms? 1. Domain Archaea 2. Domain Bacteria 3. Domain Eukarya Domain - highest taxon (group) for classification purposes Each Domain consists of Kingdom(s) Domains are based on cell type: prokaryote vs eukaryote All cellular life exists as either prokaryotic cells or eukaryotic cells  Prokaryotes - placed into 2 different Domains  Eukaryotes - placed into 1 Domain 6 Cell Types 7 The Three Domain System What is the origin of prokaryotic cells & eukaryotic cells? All cells came from a common ancestor cell called the last universal common ancestor (LUCA) LUCAs eventually evolved into 3 different cell groups called the 3 Domains! Figure 10.1 8 The Three Domain System Domain Archaea and Domain Bacteria  Contain all members of Kingdom Monera Domain Eukarya  Contain all members of the other 4 Kingdoms If all members of Kingdom Monera belong to Domain Archaea & Domain Bacteria, then how can you distinguish between members of these two Domains?..... (What is the difference between Domain Archaea & Domain Bacteria?) 9 Domain Archaea vs Domain Bacteria Domain Archaea Domain Bacteria Unusual cell walls - no peptidoglycan in cell walls Live in “extreme” habitats Cell walls with peptidoglycan Examples:  Thermophiles  Halophiles  Methanogens Live in “normal” habitats 10 The Five Kingdom System Kingdom - 2nd highest taxon Several Kingdoms can form a Domain What are the five Kingdoms of living organisms? 1. 2. 3. 4. 5. Kingdom Monera (AKA Kingdoms Prokaryotae or Bacteria) Kingdom Protista Kingdom Fungi Kingdom Plantae Kingdom Animalia 11 The Five Kingdom System Kingdom Monera Prokaryotes Unicellular Example - Bacterium (Escherichia coli) Kingdom Protista Simplest Eukaryotes Mostly unicellular Example - Amoeba (Amoeba proteus) 12 The Five Kingdom System Kingdom Fungi Eukaryotes Some unicellular, others multicellular Example - Fungus 1. Yeast (Saccharomyces cerevisiae) 2. Mold (Penicillium chrysogenum) 13 The Five Kingdom System Kingdom Plantae Eukaryotes Multicellular, autotroph, cell wall Example - Plant (Sequoiadendron giganteum - Giant Redwood) 14 The Five Kingdom System Kingdom Animalia Eukaryote Multicellular, complex, heterotroph Example - Animal  Large round worm (Ascaris lumbricoides)  Common house fly (Musca domestica) 15 Autotrophs vs Heterotrophs Autotrophs Produce own -Yes food? Heterotrophs -No Definition -Organisms that can produce their own food -Organisms that rely on consuming other organisms Types -Photoautotrophs, Chemoautotrophs -Photoheterotrophs, Chemoheterotrophs Examples -Plants, Algae -Herbivores, Carnivores, Omnivores 16 Species and Subspecies Species - lowest taxon Divided into: 1. Prokaryotic species (bacteria) 2. Eukaryotic species (non-bacteria) Eukaryotic Species A group of organisms that differ from each other but yet are closely related to each other genetically Several related species can form a Genus 17 Species and Subspecies Prokaryotic Species  A population of bacterial cells with similar characteristics  Example - Streptococcus species:  Streptococcus pneumoniae & Streptococcus pyogenes  Clones - population of bacterial cells derived from a single parent cell  All are genetically identical!  Subspecies/Strain/Serovar - members of a clone (species) are NOT genetically identical anymore; clones genetically diverged over time through genetic mutations  Subspecies/strains are identified by numbers, letters that follow the species name (Ex - E. coli O157:H7, Influenza A virus H1N5) 18 19 Classification of Viruses Viruses are not cells  “acellular” Obligate intracellular parasite Classified usually by Family, Genus and species  Family name ends in “-viridae” - Ex. Retroviridae, Herpesviridae Can have viral subspecies/strain  Example - strains of Influenza A Virus:  H1N1 (Swine Flu)  H1N5 (Avian Flu) 20 Methods of Classifying & Identifying Microbes 1. Morphological Characteristics Look at shape, arrangement & size of bacteria 2. Differential Staining Ex - Gram staining of bacterial cell wall:  Gram-Positive bacteria vs Gram-Negative bacteria  Based on chemical composition of cell wall (amount of peptidoglycan) 3. Biochemical Tests Using a pair of questions with “yes or no” answers to determine metabolic characteristics of bacteria  Ex - “Can an unknown bacterium breakdown glucose?”  Yes or No 21 Other Methods of Classification & Identification 4. Serology (study of blood serum) Serological testing - helps differentiate among strains within species by analyzing DNA sequence of the microorganism Example: pathogenic E. coli vs non-pathogenic E. coli 22 Other Methods of Classification & Identification 5. PCR (Polymerase Chain Reaction) Method used to make many copies of (amplify) a specific DNA segment from a single copy of a DNA sequence 23 Other Methods of Classification & Identification 6. Textbooks/manuals Bergey’s Manual of Determinative Bacteriology  Provides systematic schemes for identifying unknown bacteria 24