Question

Hi, can you make a dichotomous key for this

A common microbiology lab assignment is the identification of an unknown bacterial culture. When this type of lab is done, students are usually given a test tube that contains a bacterial culture, but it is only labeled with a number. The student is also given a list of bacteria that could potentially be their unknown organism along with the expected results for biochemical tests for each organism on the list.

A dichotomous key is a useful tool in this situation, because it provides a quick comparison of the biochemical test results of the unknown and the list of potential bacteria. In this lab assignment, you will prepare two dichotomous keys (one for a set of gram-positive organisms and one for a set of gram-negative organisms) that you will use in the lab 8 assignment. To make a dichotomous key, you successively divide a single group into two groups based on distinguishing criteria. For example, there are 7 gram-positive organisms in the attached chart. Five of those organisms are catalase positive and two are catalase negative. That could be the first step of a dichotomous key (a group of 7 is divided into one group of 5 and one group of 2).

Answer 1

Dichotomous key to distinguish the one set of gram postitive bacteria and another set of gram negative bacteria are as follow-

- Gram staining is the best way that can categorise these group. Since gram postive bacteria have thick peptidoglycan so they retain crystal violet even after wash with alcohol they appear purple colour while the other group those donot retain the stain and after wash appeared pink they can be classified as gram negative.

- The group of bacteria that are more susceptible to antibiotic are gram positive while those that are resistant are gram negative. So, the dichotomous key could be antibiotic susceptible or resistant.