Chapter 10: Classification of Microorganisms
Taxonomy is where we put organisms into categories, or taxa (singular: taxon), to show degrees of similarities among organisms.
Systematics, or phylogeny, is the study of the evolutionary history of organisms, and the hierarchy of taxa reflects their evolutionary, or phylogenetic, relationships.
In this widely accepted scheme, animals, plants, and fungi are kingdoms in the Domain Eukarya.
The Domain Bacteria includes all of the pathogenic prokaryotes as well as many of the nonpathogenic prokaryotes found in soil and water.
The Domain Archaea includes prokaryotes that do not have peptidoglycan in their cell walls.
According to the endosymbiotic theory, eukaryotic cells evolved from prokaryotic cells living inside one another, as endosymbionts.
In a phylogenetic tree, grouping organisms according to common properties implies that a group of organisms evolved from a common ancestor; each species retains some of the characteristics of the ancestor.
Some of the information used to classify and determine phylogenetic relationships in higher organisms comes from fossils.
A molecular clock for evolution is based on nucleotide sequences in the genomes of organisms.
Every organism is assigned two names, or a binomial.
These names are the genus name and specific epithet (species), and both names are printed underlined or italicized.
Because this system gives two names to each organism, the system is called binomial nomenclature.
A eukaryotic species is a group of closely related organisms that breed among themselves.
Just as a number of species make up a genus, related genera make up a family.
A group of similar families constitutes an order, and a group of similar orders makes up a class.
Related classes, in turn, make up a phylum.
All phyla that are related to each other make up a kingdom, and related kingdoms are grouped into a domain.
A prokaryotic species is defined simply as a population of cells with similar characteristics.
A pure culture is often a clone, a population of cells derived from a single parent cell.
All cells in the clone should be identical, but in some cases, pure cultures of the same species are not identical in all ways.
Each such group is called a strain. Strains are identified by numbers, letters, or names that follow the specific epithet.
Consequently, the organisms once classified as protists are being divided into clades, or genetically related groups.
The Kingdom Fungi includes the unicellular yeasts, multicellular molds, and macroscopic species such as mushrooms.
The Kingdom Plantae (plants) includes mosses, ferns, conifers, and flowering plants.
The kingdom of multicellular organisms called Animalia (animals) includes sponges, various worms, insects, and animals with backbones (vertebrates).
The International Committee on Taxonomy of Viruses defines a viral species as a population of viruses with similar characteristics (including morphology, genes, and enzymes) that occupies a particular ecological niche.
Transport media are usually not nutritive and are designed to prolong viability of fastidious pathogens.
Rapid identification methods are manufactured for groups of medically important bacteria, such as the enterics.
Serology is the science that studies serum and immune responses that are evident in serum.
Solutions of such antibodies used in the identification of many medically important microorganisms are commercially available; such a solution is called an antiserum.
In a procedure called a slide agglutination test, samples of an unknown bacterium are placed in a drop of saline on each of several slides.
Serological testing can differentiate not only among microbial species, but also among strains within species.
Strains with different antigens are called serotypes, serovars, or biovars.
A test called the enzyme-linked immunosorbent assay (ELISA) is widely used because it is fast and can be read by a computer scanner.
Another serological test, Western blotting, is also used to identify antibodies in a patient’s serum.
Phage typing is a test for determining to which phages a bacterium is susceptible.
Flow cytometry can be used to identify bacteria in a sample without culturing the bacteria.
Taxonomists can use an organism’s DNA base composition to draw conclusions about relatedness.
Nucleic acid amplification tests (NAATs) can be used to increase the amount of microbial DNA to levels that can be tested by gel electrophoresis.
Cladograms are maps that show evolutionary relationships among organisms.
Taxonomy is where we put organisms into categories, or taxa (singular: taxon), to show degrees of similarities among organisms.
Systematics, or phylogeny, is the study of the evolutionary history of organisms, and the hierarchy of taxa reflects their evolutionary, or phylogenetic, relationships.
In this widely accepted scheme, animals, plants, and fungi are kingdoms in the Domain Eukarya.
The Domain Bacteria includes all of the pathogenic prokaryotes as well as many of the nonpathogenic prokaryotes found in soil and water.
The Domain Archaea includes prokaryotes that do not have peptidoglycan in their cell walls.
According to the endosymbiotic theory, eukaryotic cells evolved from prokaryotic cells living inside one another, as endosymbionts.
In a phylogenetic tree, grouping organisms according to common properties implies that a group of organisms evolved from a common ancestor; each species retains some of the characteristics of the ancestor.
Some of the information used to classify and determine phylogenetic relationships in higher organisms comes from fossils.
A molecular clock for evolution is based on nucleotide sequences in the genomes of organisms.
Every organism is assigned two names, or a binomial.
These names are the genus name and specific epithet (species), and both names are printed underlined or italicized.
Because this system gives two names to each organism, the system is called binomial nomenclature.
A eukaryotic species is a group of closely related organisms that breed among themselves.
Just as a number of species make up a genus, related genera make up a family.
A group of similar families constitutes an order, and a group of similar orders makes up a class.
Related classes, in turn, make up a phylum.
All phyla that are related to each other make up a kingdom, and related kingdoms are grouped into a domain.
A prokaryotic species is defined simply as a population of cells with similar characteristics.
A pure culture is often a clone, a population of cells derived from a single parent cell.
All cells in the clone should be identical, but in some cases, pure cultures of the same species are not identical in all ways.
Each such group is called a strain. Strains are identified by numbers, letters, or names that follow the specific epithet.
Consequently, the organisms once classified as protists are being divided into clades, or genetically related groups.
The Kingdom Fungi includes the unicellular yeasts, multicellular molds, and macroscopic species such as mushrooms.
The Kingdom Plantae (plants) includes mosses, ferns, conifers, and flowering plants.
The kingdom of multicellular organisms called Animalia (animals) includes sponges, various worms, insects, and animals with backbones (vertebrates).
The International Committee on Taxonomy of Viruses defines a viral species as a population of viruses with similar characteristics (including morphology, genes, and enzymes) that occupies a particular ecological niche.
Transport media are usually not nutritive and are designed to prolong viability of fastidious pathogens.
Rapid identification methods are manufactured for groups of medically important bacteria, such as the enterics.
Serology is the science that studies serum and immune responses that are evident in serum.
Solutions of such antibodies used in the identification of many medically important microorganisms are commercially available; such a solution is called an antiserum.
In a procedure called a slide agglutination test, samples of an unknown bacterium are placed in a drop of saline on each of several slides.
Serological testing can differentiate not only among microbial species, but also among strains within species.
Strains with different antigens are called serotypes, serovars, or biovars.
A test called the enzyme-linked immunosorbent assay (ELISA) is widely used because it is fast and can be read by a computer scanner.
Another serological test, Western blotting, is also used to identify antibodies in a patient’s serum.
Phage typing is a test for determining to which phages a bacterium is susceptible.
Flow cytometry can be used to identify bacteria in a sample without culturing the bacteria.
Taxonomists can use an organism’s DNA base composition to draw conclusions about relatedness.
Nucleic acid amplification tests (NAATs) can be used to increase the amount of microbial DNA to levels that can be tested by gel electrophoresis.
Cladograms are maps that show evolutionary relationships among organisms.
