MT2 > Classification of Infectious Agents

Question 1

Define Taxonomy.

Answer 1

The science of classifying organisms.

Question 2

Define Phylogeny (systematics).

Answer 2

The study of the evolutionary history of organisms.

Question 3

Who came up with the binomial naming convention we use today? When?

Answer 3

Carl Linnaeus in 1735.

Question 4

What were the two original kingdoms identified by Linnaeus?

Answer 4

Plantae and Animalia.

Question 5

What domains were eventually proposed by Woese in 1978 and universally adopted?

Answer 5

Eukarya, Archaea, Bacteria.

Question 6

Which domains of organisms have membrane lipids which are composed of straight carbon chains attached to glycerol by an ester linkage?

Answer 6

Bacteria and Eukarya.

Question 7

Which domains of organisms have membrane lipids which are composed of branched carbon chains attached to glycerol by an ether linkage?

Answer 7

Archaea.

Question 8

What is the purpose of a phylogenetic tree?

Answer 8

To group organisms according to their evolution from a common ancestor.

Question 9

With regards to prokaryotic species, what is a culture?

Answer 9

A colony of bacteria grown in laboratory media.

Question 10

With regards to prokaryotic species, what is a clone?

Answer 10

A population of cells derived from a single parent cell.

Question 11

With regards to prokaryotic species, what is a strain?

Answer 11

Within a clone, a group of genetically different cells (may have diverged though mutation).

Question 12

What are the common characteristics of Protista?

Answer 12

A catchall kingdom for variety of autotrophic and heterotrophic organisms.

Question 13

What are the common characteristics of Fungi?

Answer 13

Chemoheterotrophic, unicellular or multicellular, cell wall of chitin, develop spores.

Question 14

What are the common characteristics of Plantae?

Answer 14

Multicellular, cellulose cell walls, undergo photosynthesis.

Question 15

What are the common characteristics of Animalia?

Answer 15

Multicellular, no cell walls, chemoheterotrophic.

Question 16

What is a “viral species”?

Answer 16

Not a part of any domain, not composed of cells, non-living. A species consists of viruses with similar characteristics sharing an ecological niche.

Question 17

What differentiates classification and identification?

Answer 17

Classification: placing organisms in groups of related species
Identification: matching an unknown organism to a list of known organisms

Question 18

What information does Bergey’s Manual of Determinative Bacteriology provide?

Answer 18

Identification schemes for identifying bacteria and archaea.

Question 19

What information does the Approved Lists of Bacterial Names provide?

Answer 19

It lists bacterial species of known classification.

Question 20

What 3 major approaches can be used to identify microorganisms?

Answer 20

1. Differentiate by morphology
2. Differential staining
3. Biochemical tests

Question 21

Under what circumstance should differential staining not be used to identify a microorganism?

Answer 21

When trying to identify a bacteria without a cell wall.

Question 22

What is meant by a “rapid identification method”?

Answer 22

A test which combines several biochemical tests into one, streamlining the identification process.

Question 23

Define “serology”.

Answer 23

The science that studies serum and immune responses in serum.

Question 24

What is the purpose of an antiserum? How does it work?

Answer 24

To identify an unknown bacterium by testing it in a solution of known antibodies.

Question 25

What is the purpose of a slide agglutination test? How does it work?

Answer 25

To identify an unknown bacterium by testing the agglutination of the bacteria in response to known antibodies.

Question 26

What is the purpose of serological testing in epidemiology?

Answer 26

To differentiate between species and strains within species when identifying an unknown microorganism.

Question 27

What is the purpose of an ELISA test in epidemiology? How does it work?

Answer 27

To identify an unknown bacterium by testing it in a microplate with many wells, each filled with a specific antibody and enzyme.

Question 28

What is the purpose of phage typing in epidemiology? How are the results observed?

Answer 28

To determine which phages a bacterium is susceptible to. On a plate, “plaques” appear where phages have lysed the bacterial cells.

Question 29

What is meant by FAME? Why is this of interest to epidemiologists?

Answer 29

Fatty Acid Methyl Esters. The FAME profile is constant and unique for a particular species of microorganism, and can be used for identification.

Question 30

How can we use flow cytometry to differentiate between bacterial species?

Answer 30

By observing differences in electrical conductivity or fluorescence between species.

Question 31

How does a fluorescence-activated cell sorter (FACS) organize cells?

Answer 31

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.

Question 32

How is DNA fingerprinting used in epidemiology?

Answer 32

By comparing digested fragments of DNA from different organisms we can see genetic similarities and differences.

Question 33

How are the unique fatty acid methyl esters (FAME) of a bacterium identified?

Answer 33

First with gas chromatography and then with a flame ionization detector.

Question 34

When might nucleic acid amplification tests (NAATs) be used?

Answer 34

When a microorganism cannot be cultured.

Question 35

What can nucleic acid hybridization be used to determine? How? What test is based on this principle?

Answer 35

The degree of relatedness of two organisms is shown by how well their DNA strands hybridize. Called a DNA chip or microarray.

Question 36

Define “ribotyping”.

Answer 36

Probing a bacterial genome with a 16S rRNA gene probe to identify it.

Question 37

How can fluorescence in-situ hybridization (FISH) be used in epidemiology?

Answer 37

To determine the identity, abundance, and relative activity of microorganisms in an environment.