Dichotomous Keys: Overview, Practice

Why is microscopy not sufficient to identify microorganism?

Microscopy provides only visual clues, and many bacteria share the same visual characteristics.

When is bacterial identification of an unknown useful?

to identify the bacterium responsible for a particular disease

to identify an unknown bacterium in an environmental sample responsible for degrading an environmental pollutant

to identify the bacteria responsible for fermenting a sugar in a particular food product

all of the above

The main method of identifying unknown bacteria identification is ___________.

biochemical tests

A dichotomous key _____________.

is a series of paired statements, of which only one applies to the unknown in question.

is a rapid and reliable method for identifying bacterial unknowns.

relies heavily on biochemical tests.

all of the above

What is the first question to be asked for a dichotomous key?

Gram stain results

Based on this dichotomous key, how many questions must be answered to identify a bacterium of the genus Streptococcus?

two

How is the ability of an organism to ferment lactose determined?

a change in the color of the medium from red to yellow

Based on this dichotomous key, which of the following are characteristics of Neisseria?

Gram-negative cocci that can tolerate oxygen

What is the name of the test used to determine if a bacterium can produce acetoin?

Vogues-Proskauer test

How are the questions in a dichotomous key phrased?

as yes/no statements, allowing for multiple characteristics to be applied to an unknown specimen

Flowcharts constructed from dichotomous keys ___________.

allow the investigator to show the relationships between the different statements.

The flowchart shown in the animation ________________.

shows all possible outcomes for the dichotomous key based on the limited number of bacteria listed.