Download Classification of Microbes - Principles of Microbiology - Lecture Slides and more Slides Microbiology in PDF only on Docsity! Classification of microbes (and other living things) Docsity.com Major events in the history of life: life was originally microscopic and unicellular Docsity.com How is classification achieved? • Observation – Similarities and differences – Fossil record • Molecular analysis – DNA – Ribosomal RNA – Mitochondrial DNA – Proteins Docsity.com Ideas about classification have changed • Linnaeus- plants and animals (1735) • Where do bacteria and fungi belong? – Von Nägeli- with plants (1857) – Haeckel- Kingdom Protista (1866) • Whitaker – five kingdoms (1969) • Woese- domains (1978) Docsity.com Classification may change again
(a) The five-kingdom system
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(b) The three-domain system
(c) How many kingdoms?
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Classification of prokaryotes • Morphology (Gram-staining) • Nutrition • Metabolism • Environmental niche • rRNA sequences (all living cells have them) • Reference: Bergey’s Manual of Systematic Bacteriology; Bergey’s Manual of Determinative Bacteriology) • Most prokaryotes have not been discovered! Docsity.com Microbial identification • Differential media • Biochemical testing • Serology • Phage typing • Genetic testing – rRNA sequencing Docsity.com A dichotomous key • Classic tool for identification • Most of these tests can be administered simultaneously • Different keys can be developed for groups of bacteria Docsity.com Classification of eukaryotes • Plantae- mosses, ferns, conifers, flworing plants (some algae) – multicellular, photosynthetic • Animalia- sponges, worms, various vertebrates and invertebrates – multicellular, ingest nutrients • Fungi (1959)- yeasts, molds, mushrooms – Absorb nutrients, form hyphae if multicellular • Protists- unicellular organisms – Don’t fit anywhere else! Docsity.com Classification of viruses • Not cellular, so are not classified in hierarchical system • Viral species- population of viruses with similar characteristics and that occupy a particular ecological niche Docsity.com Summary • Eukaryotes are much more diverse than prokaryotes • Some have evolved much more recently than others • All are “successful” in their niche • Classification is an ongoing process • Genetic and phenotypic differences are considered in classification Docsity.com
