Classification. Classification GROUPING things according to their CHARACTERISTICS.
Classification of microbes (and other living things)
description
Transcript of Classification of microbes (and other living things)
Classification of microbes (and other living things)
Major events in the history of life:life was originally microscopic and
unicellular
Taxonomy: the science of naming and classifying organisms (Carolus Linnaeus)
Phylogeny: evolutionary history
Systematics: the science of classification basedon evolutionary history of organisms
Linnaean classification system is used today (with modifications)
• Binomial (“scientific name”)– Genus and species
names (specific epithet)
• Hierarchical classification
How is classification achieved?
• Observation– Similarities and differences– Fossil record
• Molecular analysis – DNA – Ribosomal RNA– Mitochondrial DNA– Proteins
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)
Classification may change again
Classification by RNA sequence data
Phenotypes (physical differences) between the domains
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!
Microbial identification
• Differential media• Biochemical testing• Serology• Phage typing• Genetic testing
– rRNA sequencing
A dichotomous key
• Classic tool for identification
• Most of these tests can be administered simultaneously
• Different keys can be developed for groups of bacteria
How do you make bacteria look different?
Genomic analysis Phage typing
Archaea: “extreme bacteria”
• Discovered in late 1970’s• Species live at extreme temperature, pH,
have unusual metabolic properties• Hard to study
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!
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
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