MT2 > Classification of Infectious Agents Flashcards
Define Taxonomy.
The science of classifying organisms.
Define Phylogeny (systematics).
The study of the evolutionary history of organisms.
Who came up with the binomial naming convention we use today? When?
Carl Linnaeus in 1735.
What were the two original kingdoms identified by Linnaeus?
Plantae and Animalia.
What domains were eventually proposed by Woese in 1978 and universally adopted?
Eukarya, Archaea, Bacteria.
Which domains of organisms have membrane lipids which are composed of straight carbon chains attached to glycerol by an ester linkage?
Bacteria and Eukarya.
Which domains of organisms have membrane lipids which are composed of branched carbon chains attached to glycerol by an ether linkage?
Archaea.
What is the purpose of a phylogenetic tree?
To group organisms according to their evolution from a common ancestor.
With regards to prokaryotic species, what is a culture?
A colony of bacteria grown in laboratory media.
With regards to prokaryotic species, what is a clone?
A population of cells derived from a single parent cell.
With regards to prokaryotic species, what is a strain?
Within a clone, a group of genetically different cells (may have diverged though mutation).
What are the common characteristics of Protista?
A catchall kingdom for variety of autotrophic and heterotrophic organisms.
What are the common characteristics of Fungi?
Chemoheterotrophic, unicellular or multicellular, cell wall of chitin, develop spores.
What are the common characteristics of Plantae?
Multicellular, cellulose cell walls, undergo photosynthesis.
What are the common characteristics of Animalia?
Multicellular, no cell walls, chemoheterotrophic.
What is a “viral species”?
Not a part of any domain, not composed of cells, non-living. A species consists of viruses with similar characteristics sharing an ecological niche.
What differentiates classification and identification?
Classification: placing organisms in groups of related species
Identification: matching an unknown organism to a list of known organisms
What information does Bergey’s Manual of Determinative Bacteriology provide?
Identification schemes for identifying bacteria and archaea.
What information does the Approved Lists of Bacterial Names provide?
It lists bacterial species of known classification.
What 3 major approaches can be used to identify microorganisms?
- Differentiate by morphology
- Differential staining
- Biochemical tests
Under what circumstance should differential staining not be used to identify a microorganism?
When trying to identify a bacteria without a cell wall.
What is meant by a “rapid identification method”?
A test which combines several biochemical tests into one, streamlining the identification process.
Define “serology”.
The science that studies serum and immune responses in serum.
What is the purpose of an antiserum? How does it work?
To identify an unknown bacterium by testing it in a solution of known antibodies.
What is the purpose of a slide agglutination test? How does it work?
To identify an unknown bacterium by testing the agglutination of the bacteria in response to known antibodies.
What is the purpose of serological testing in epidemiology?
To differentiate between species and strains within species when identifying an unknown microorganism.
What is the purpose of an ELISA test in epidemiology? How does it work?
To identify an unknown bacterium by testing it in a microplate with many wells, each filled with a specific antibody and enzyme.
What is the purpose of phage typing in epidemiology? How are the results observed?
To determine which phages a bacterium is susceptible to. On a plate, “plaques” appear where phages have lysed the bacterial cells.
What is meant by FAME? Why is this of interest to epidemiologists?
Fatty Acid Methyl Esters. The FAME profile is constant and unique for a particular species of microorganism, and can be used for identification.
How can we use flow cytometry to differentiate between bacterial species?
By observing differences in electrical conductivity or fluorescence between species.
How does a fluorescence-activated cell sorter (FACS) organize cells?
A laser detects the fluorescently labelled cells, which are then given a positive charge by an electrode. These are then sorted by charge into positive or neutral collection tubes.
How is DNA fingerprinting used in epidemiology?
By comparing digested fragments of DNA from different organisms we can see genetic similarities and differences.
How are the unique fatty acid methyl esters (FAME) of a bacterium identified?
First with gas chromatography and then with a flame ionization detector.
When might nucleic acid amplification tests (NAATs) be used?
When a microorganism cannot be cultured.
What can nucleic acid hybridization be used to determine? How? What test is based on this principle?
The degree of relatedness of two organisms is shown by how well their DNA strands hybridize. Called a DNA chip or microarray.
Define “ribotyping”.
Probing a bacterial genome with a 16S rRNA gene probe to identify it.
How can fluorescence in-situ hybridization (FISH) be used in epidemiology?
To determine the identity, abundance, and relative activity of microorganisms in an environment.
