Taxonomy, Classification, and Identification of Organisms

These flashcards review key points from the lecture on taxonomy, three-domain classification, naming conventions, strains vs. species, and laboratory identification methods.

Who is credited with creating the modern, widely-used system of taxonomy?

Carl Linnaeus

In binomial nomenclature, which word is capitalized, genus or species?

The genus is capitalized; the species is never capitalized.

How should scientific names be formatted when typed and when handwritten?

Typed names are italicized; handwritten names are underlined.

Why is "Bacillus" with a capital "B" very different from "bacillus" with a lowercase "b"?

"Bacillus" (capital B) refers to a specific genus of spore-forming aerobic bacteria, while "bacillus" (lowercase b) simply describes any rod-shaped bacterium.

What are the two most specific ranks used in binomial nomenclature?

Genus and species

Do humans have subspecies according to genetic evidence?

No; Homo sapiens is a single, relatively homogeneous species with no valid subspecies.

What taxonomic rank is more specific than species in domestic dogs?

Breed

Why can dogs and wolves interbreed and produce fertile offspring?

They are both members of the same species complex (Canis lupus) and have not diverged enough genetically to cause sterility.

In bacteria, what term parallels the idea of "breed" in dogs?

Strain

Give an example of a pathogenic E. coli strain and the disease it causes.

E. coli O157:H7 can cause hemorrhagic dysentery.

Which Vibrio cholerae strain was introduced into Haiti after the 2010 earthquake?

The L-tor biotype

What do the species names "domesticus" or "familiaris" usually indicate?

That the organism has been domesticated by humans (e.g., Canis familiaris, Bos domesticus).

What is the scientific name of the common red fox?

Vulpes vulpes

Which rat species replaced Rattus rattus in Europe and is less effective at spreading plague?

Rattus norvegicus (the Norway or sewer rat)

What does the abbreviation "E. coli" stand for?

Escherichia coli

MRSA is short for what full scientific name?

Methicillin-resistant Staphylococcus aureus

C. diff is the shorthand for which bacterium?

Clostridioides (Clostridium) difficile

How many domains are recognized in the current three-domain system?

Three: Bacteria, Archaea, and Eukarya

What unique cell-wall molecule is found only in true bacteria?

Peptidoglycan

Which domain contains organisms with membranes made of unique long-chain lipids that tolerate extreme environments?

Archaea

Are any Archaea known to be pathogenic to humans?

No, no pathogenic Archaea have been identified.

Name the two most common bacterial shapes.

Bacillus (rod) and coccus (sphere)

What form of reproduction do bacteria use?

Binary fission (asexual cloning)

Which cellular structure provides motility to bacteria?

Flagella

What is the primary criterion used in the Baltimore system for classifying viruses?

Type of nucleic acid (DNA or RNA) and whether it is single-stranded or double-stranded.

Why are hepatitis A, B, C, and E viruses placed in different virus families?

Because their genetic material and replication strategies differ, even though they cause similar liver diseases.

List the three main laboratory approaches for identifying unknown microbes.

Phenotyping, serological (immunological) testing, and genotyping (molecular).

What is a major advantage of phenotyping?

It requires minimal training and inexpensive equipment.

What is a key limitation of serological tests?

They are highly specific and only detect organisms for which a matching antibody is provided.

Why is genotyping considered the most accurate identification method?

It examines the organism’s actual DNA sequence, leaving little room for error.

Name the stain that divides bacteria into Gram-positive and Gram-negative.

The Gram stain

What three hemolysis patterns can be observed on sheep blood agar?

Beta (complete clearing), alpha (green partial clearing), and gamma (no clearing).

Which opportunistic pathogen produces a distinctive green pigment on culture plates and infected wounds?

Pseudomonas aeruginosa

What simple lab tool guides the choice of subsequent biochemical tests in a phenotype workflow?

A dichotomous key

When using colony morphology, what features might you record?

Shape, edge, elevation, surface texture, and pigment production

What does “serotype” literally refer to?

A classification based on antigen–antibody reactions (sero = serum/immune).