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Chapter 10
Microbiology
| Term | Definition |
|---|---|
| Taxonomy consists of three interrelated areas: | Identification, classification, and nomenclature. |
| Strategies used to identify Microorganisms | To characterize and identify microorganisms, a wide assortment of technologies is used, including microscopic examination, cultural characteristics, biochemical tests, and nucleic acid analysis. |
| Strategies used to classify Microorganisms | Taxonomic classification categories are arranged in a hierarchical order, with the species being the basic unit. Taxonomic categories include Domain, Kingdom, Phylum, Class, Order, Genus, Species. Individual strains within a species vary in properties. |
| Nomenclature | Microorganisms are assigned names governed by official rules. |
| Microscopic Morphology | The size, shape, and staining characteristics of a microorganism yield important clues as to its identity. |
| Culture Characteristics | Selective and differential media used in the isolation process can provide information that helps identify an organism. |
| Metabolic Capabilities | Most biochemical tests rely on a pH indicator or chemical reaction that shows color change when a compound is degraded. The basic strategy for identification using biochemical tests relies on the use of a dichotomous key. |
| Serological Testing | Proteins and polysaccharides that make up a prokaryote's surface are sometimes characteristic enough to be identifying markers. |
| Protein Profile | MALDI-TOF MS (matrix assisted laser desorption ionization time of flight mass spectrometry) generates a profile of a colony's proteins and macromolecules, which can be used to identify the organism. |
| Detecting specific nucleotide sequences | A probe complementary to a sequence unique to a given microbe is used to detect that organism. Nucleic acid amplification tests, such as PCR increase the number of copies of a specific nucleotide sequence, thereby determining if an organism is present |
| Sequencing ribosomal RNA Genes | The nucleotide sequence of ribosomal RNA (rRNA) can be used to identify prokaryotes. Newer techniques simply sequence rDNA, the DNA that encodes rRNA. Organisms that cannot yet be cultivated can be identified by amplifying, cloning, and then sequencing |
| Biochemical Typing | A group of strains that has a characteristic biochemical variation is called biovar, or a biotype. |
| Serological Typing | A group of strains that differs serologically from other strains is called a serovar, or a serotype. |
| Molecular Typing | Two isolates that have different restriction fragment length polymorphisms are considered different strains. Multilocus sequence typing determines the nucleotide sequence of representative segments. Whole-genome sequencing can be used to compare isolates. |
| Phage Typing | The suspectibility to various types of bacteriophages can be used to demonstrate strain differences. |
| Antibiograms | antimicrobial suspectibility patterns can be used to distinguish strains. |
| Classifying Microorganisms | DNA sequences can be used to construct a phylogenetic tree. |
| Horizontal gene transfer | can complicate insights provided by some types of DNA sequence comparison. |
| rDNA Sequence Analysis | Analyzing and comparing the sequences of rRNA and more recently, rDNA, has revolutionized the classification of organisms. |
| DNA Hybridization | The extent of nucleotide similarity between two organisms can be determined by measuring how completely single strands of their DNA will anneal to one another. |
| G + C content | The G + C content can be measured by determining the temperature at which double-stranded DNA melts. |
| Phenotypic Methods | Classification schemes that group microorganisms by phenotype have largely been replaced by methods that rely on SSU rDNA sequence data. |
| One way to roughly compare the genomes of different bacteria is | To determine their G + C content, which is the G-C base pairs in an organism. |
| DNA sequences makes it possible to more accurately construct a | phylogenetic tree. |
| DNA sequences are viewed as | evolutionary chronometers (meaning they provide a relative measure of the time elapsed since two organisms diverged from a common ancestor). |
| The goal of phylogenetic classification is to | group organisms according to their evolutionary relatedness. |
| Phenotypically similar organisms may be only _____; conversely, those that appear dissimilar may be _____ | distantly related; closely related. |
| Multilocus sequence typing | A procedure where the DNA sequences of portions of certain common genes are determined, and these are used for comparison. |
| Serovar or Serotype | A group of strains that have cell surface antigens different from other strains. |
| The ability to distinguish different strains of a given species is useful in some situations, particularly when tracking the source of ____ | Foodborne diseases. |
| Characterizing strain differences also plays an important role in | forensic investigations of bioterrorism, and other biocrimes, and in diagnosing certain diseases. |
| Biovar or Biotype | A group of strains that have a characteristic biochemical pattern. |
| Nucliec acid amplification tests | can be used to increase the number of copies of specific DNA sequences that serve as identifying marker. |
| A DNA probe can be used to | detect the amplified DNA. |
| Fluorescence in situ hybridzation | often uses probes that bind 16S ribosomal RNA (rRNA). |
| Signature Sequence | Is a nucleotide sequence in rRNA that characterizes either a certain species or a group of related organisms. |
| Nucleic Acid Probes and Nucleic acid amplification tests | Detect specific DNA sequences. |
| MALDI-TOF MS | is particularly important particularly important in clinical labs where rapid identification of bacterial isolates is crucial for patient care. |
| MALDI-TOF | is a type of mass spectrometry, which is used to determine the chemical composition of a sample by measuring the masses of various components. |
| Dichotomous key | A series of alternative choices that lead to the identification of an organism. |
| The basic strategy for identifying bacteria based on biochemical tests relies on a________ | dichotomous key |
| A variety of biochemical tests can be used to determine an isolate's metabolic capabilities. | A variety of biochemical tests can be used to determine an isolate's metabolic capabilities. |
| Colony morphology can give initial clues to the identity of the organism. | Colony morphology can give initial clues to the identity of the organism. |
| The Gram stain | Distinguishes between gram-positive and gram-negative bacteria. |
| Gram stain results..... | give enough information to just to start appropriate antimicrobial treatment. |
| Size and Shape of a Microorganism can easily be determined_____ | Microscopically. (shape and size helps to identify its kingdom and if it is a prokaryote) |
| Bacteria and archaea are given names according to a set of internationally recognized rules ________ | International Code of Nomenclature of Bacteria. |
| Taxonomy | the science of characterizing and naming organisms in order to arrange them into hierarchical groups. Organisms with similar properties are grouped together and separated from ones that are different. |
| Taxonomy can be viewed as three seperate but interrelated areas: | Identification, Classification, Nomenclature. |
| Identification | The process of characterizing an isolate (a population of cells descended from a single cell) to determine the group (taxon) to which it belongs. |
| Classification | The process of arranging organisms into similar or related groups, primarily to make it easier to identify them for study. |
| Nomenclature | The system of assigning names to organisms. |
| Species | A group of closely related strains. |
| Genus | A collection of similar species. |
| Family | A collection of similar genera. In prokaryotic nomenclature, the name of the family ends in the suffix -aceae. |
| Order | A collection of similar families. In prokaryotic nomenclature, the name of the order ends in the suffix -ales. |
| Class | A collection of similar orders. |
| Phylum or Division | A collection of similar classes. |
| Kingdom | A collection of similar phyla or divisions |
| Domain | A collection of similar kingdoms. The domain reflects the characteristics of the cells that make up the organism. |
| rDNAs | the genes that encode ribosomal RNA. |
| PulseNet | Catalogs the RFLPs (restriction fragment length polymorphisms) of certain foodborne bacterial pathogens. |
Created by:
wayjavie