Transcript Chapter 13
Chapter 4 Microscopy, Staining, and Classification 6/30/11 MDufilho Classification and Identification of Microorganisms – Taxonomy consists of classification, nomenclature, and identification – Organize large amounts of information about organisms – Make predictions based on knowledge of similar organisms 6/30/11 MDufilho 2 Classification and Identification of Microorganisms • Linnaeus and Taxonomic Categories – Linnaeus – Classified organisms based on characteristics in common – Organisms that can successfully interbreed called species – Used binomial nomenclature in his system – Linnaeus proposed only two kingdoms 6/30/11 © 2012 Pearson Education Inc. MDufilho 3 Figure 4.22 Levels in a Linnaean taxonomic scheme-overview Domain Bacteria Archaea Eukarya Animalia Plantae Fungi Kingdom Phylum Chordata (vertebrates) Arthropoda (joint-legged animals) Platyhelminthes Nematoda (tapeworm) (unsegmented roundworms) Class Insecta Crustacea Arachnida Order Scorpionida Parasitiformes (mites and ticks) Acariformes (mites) Araneida Family Ixodidae (hard ticks) Argasidae (soft ticks) Ixodes Rhipicephalus Genus Dermacentor Species 6/30/11 l. scapularis (deer tick) MDufilho l. pacificus (black-eyed tick) l. ricinus (castor bean tick) 4 Classification and Identification of Microorganisms • Linnaeus and Taxonomic Categories – Linnaeus proposed only two kingdoms – Later taxonomic approach based on five kingdoms – Animalia, Plantae, Fungi, Protista, and Prokaryotae 6/30/11 © 2012 Pearson Education Inc. MDufilho 5 Classification and Identification of Microorganisms • Linnaeus and Taxonomic Categories – Linnaeus’s goal was to classify organisms to catalogue them – Modern goal is to understand relationships among groups of organisms – Reflect phylogenetic hierarchy – Emphasis on comparison of organisms’ genetic material – Led to proposal to add domain 6/30/11 © 2012 Pearson Education Inc. MDufilho 6 Classification and Identification of Microorganisms • Domains – Carl Woese compared nucleotide sequences of rRNA subunits – Proposal of three domains as determined by ribosomal nucleotide sequences – Eukarya, Bacteria, and Archaea – Cells in the three domains differ by other characteristics 6/30/11 © 2012 Pearson Education Inc. MDufilho 7 Classification and Identification of Microorganisms • Taxonomic and Identifying Characteristics – – – – – Physical characteristics Biochemical tests Serological tests Phage typing Analysis of nucleic acids 6/30/11 © 2012 Pearson Education Inc. MDufilho 8 Figure 4.23 Two biochemical tests for identifying bacteria-overview Gas bubble Acid with gas 6/30/11 Inverted tubes to trap gas Acid with no gas Inert MDufilho Hydrogen sulfide produced No hydrogen sulfide 9 Figure 4.25 An agglutination test, one type of serological test-overview 6/30/11 Negative result Positive result Negative result Positive result MDufilho 10 Figure 4.26 Phage typing Bacterial lawn Plaques 6/30/11 MDufilho 11 Classification and Identification of Microorganisms • Taxonomic Keys – Dichotomous keys – Series of paired statements where only one of two “either/or” choices applies to any particular organism – Key directs user to another pair of statements, or provides name of organism 6/30/11 © 2012 Pearson Education Inc. MDufilho 12 Figure 4.27 Use of a dichotomous taxonomic key-overview Gram-positive cells? No Yes Gram-positive bacteria Rod-shaped cells? No Yes Can tolerate oxygen? Cocci and pleomorphic bacteria No Yes Ferments lactose? Obligate anaerobes No Yes Non-lactosefermenters Can use citric acid (citrate) as sole carbon source? No Yes Produces gas from glucose? No Shigella Produces hydrogen sulfide gas? No Yes Escherichia Produces acetoin? No Citrobacter 6/30/11 MDufilho Yes Salmonella Yes Enterobacter 13