Classification of Microorganisms PDF

Classification of Microorganisms  Taxonomy Taxonomy is the science of naming and classifying organisms Organisms are grouped according to common properties such as: Common anatomy and highly-similar DNA and rRNA sequences When organisms are grouped together, it impli...

Classification of Microorganisms  Taxonomy Taxonomy is the science of naming and classifying organisms Organisms are grouped according to common properties such as: Common anatomy and highly-similar DNA and rRNA sequences When organisms are grouped together, it implies that they evolved from a common ancestor  Taxonomy Provides a reference for identifying organisms Facilitates research, scholarship, and worldwide communication Provides universal names for organisms Scientific nomenclature  Taxonomic Hierarchy All cellular organisms can be grouped into a series of subdivisions that make up a taxonomic hierarchy This is based on evolution and relatedness to one another Domain Kingdom Phylum Class Order Family Genus Scientific name Species  The Three-Domain System All organisms are initially classified by cell type  First Cells The oldest fossils are of prokaryotes Fossils from 3.0 - 3.5 billion years ago were found in Australia This evidence suggests the first cell was a prokaryote  Eukaryotic Cells Eukaryotic cells evolved later, approximately 1.4 billion years ago How did eukaryotic cells become so complex and where did their organelles originate?  Endosymbiotic Theory The endosymbiotic theory states that some of the organelles (mitochondria and chloroplasts) in today’s eukaryotic cells were once prokaryotic microbes  Endosymbiotic Theory The endosymbiotic theory describes how a large host cell and ingested bacteria could become dependent on one another for survival, resulting in a permanent relationship Over millions of years of evolution, mitochondria and chloroplasts have become more specialized, and today they cannot live outside the cell Endosymbiotic Theory  Evidence for Endosymbiotic Theory There is fascinating evidence that mitochondria and chloroplasts were once primitive bacteria: Both organelles contain a double membrane – the outer membrane may be derived from the engulfing vesicle, and the inner membrane may be derived from the plasma membrane of the original prokaryote  Evidence for Endosymbiotic Theory There is fascinating evidence that mitochondria and chloroplasts were once primitive bacteria: Like bacteria, both mitochondria and chloroplasts have their own DNA, a single circular chromosome Like bacteria, both mitochondria and chloroplasts have their own 70S ribosomes Like bacteria, both mitochondria and chloroplasts divide by binary fission These organelles are the same size as Questions to think about What is taxonomy? In the 3 domain system how are all organisms initially classified? What are the 3 domains? The first fossils are of what type of cells? What does this suggest? What is the endosymbiotic theory? What evidence supports this theory? Classification of Organisms  Classification of Eukaryotes Kingdoms of the Domain Eukarya: Animalia: Multicellular; no cell walls; use organic molecules for energy and carbon sources Microbes: Multicellular animal parasites Plantae: Multicellular; cellulose cell walls; usually use light for energy and CO2 as carbon sources Microbes: Algae Fungi: Unicellular or multicellular; cell walls of chitin; develop from spores or hyphal fragments; use organic molecules for energy and carbon sources Microbes: Yeasts and molds Protista: Most are single-celled. Other than this feature, they have very little in common. Microbes: Protozoa Phylogenetic Relationships of Prokaryotes  Classification of Prokaryotes at the Species Level For eukaryotes, scientists define a species as a group of organisms that can interbreed and have fertile offspring. This definition doesn’t apply to prokaryotes, which reproduce asexually Prokaryotic species are determined based on close similarities in appearance, physiology, and genes  Classification of Prokaryotes at the Species Level A prokaryote strain is a subgroup of a species that possesses a trait that distinguishes it from other members of the species Strain designations are used to indicate differences in pathogenicity or to characterize a disease outbreak or strains of medical interest Identified by numbers, letters, etc. Example: Escherichia Strain coli O157:H7 designation  Classification of Viruses Viruses are not classified in the 3 domain system They are not composed of cells and cannot replicate on their own For this reason, they are classified in their own taxonomic system Since they are obligate parasites, they must have evolved more recently, after the evolution of a host cell Questions to think about What are the kingdoms of the domain Eukarya and which microorganisms belong to each? What is a protist? How is a prokaryotic species classified? Why are viruses not included in the 3 domain system? Methods of Bacterial Classification and Identification  Classification of Bacteria If you were to discover an organism, which is not currently categorized in our taxonomic system, there are four major methods to allow you to characterize and classifying that organism: Phenotypic classification Metabolic classification Antigenic classification Genotypic classification Phenotypic Classification of Bacteria Macroscopic distinction: Size and shape of the colonies Pigmentation of the colonies Microscopic distinction: Shape of individual organism (e.g. cocci, bacilli, curved or spiral) Ability to retain gram stain (e.g., gram + or gram -)  Metabolic Classification of Bacteria Requirement for oxygen Anaerobe vs. aerobe Requirement for specific nutrients Carbon sources required, etc. Production of specific metabolic products Acid, alcohols, etc. Production of specific enzymes Catalase, coagulase, etc.  Antigenic Classification of Bacteria Serotyping A particular strain may be distinguished using antibodies to bind to and thus detect the presence of unique molecules on the bacterial surface Example: Allows distinction between strains of E. coli of the microbiota from E. coli O157:H7  Genotypic Classification of Bacteria Most precise method for classifying bacteria Distinguish bacteria by detection of specific DNA sequences Rapid, does not require the presence of live or abundant bacteria Questions to think about What are the 4 methods of classifying bacteria? If an example is given, you should be able to determine which of the 4 it is.