Microbiology 102 – Experiment 7:
|
organism | gram rx. |
cellular shape & arrange- ment |
glucose fermen- tation* |
lactose fermen- tation* |
nitrate reduc- tion to nitrite |
nitrate reduc- tion to N2 |
motility | indole produc- tion |
starch hydro- lysis |
catalase rx. |
some notes on colonial characteristics |
Escherichia coli |
– | short rods | FG | FG | + | – | + | + | – | + | Note that only two (SM and ML) are brightly pigmented (dark red and canary yellow, respectively). Also, PF has a yellowish-green pigment that diffuses into the medium. Your unknown would not be any of those organisms if you did not see that pigment. The other species on the list are generally whitish to gray. Of the three gram-positive cocci, SE has small, white, opaque colonies; EF has small, gray, translucent colonies; ML has small, canary-yellow, opaque colonies. |
Klebsiella pneumoniae |
– | short rods | FG | FG | + | – | – | – | – | + | |
Serratia marcescens |
– | short rods | FG or F | (F) or – | + | – | + | – | – | + | |
Pseudomonas fluorescens |
– | rods | – | – | – | + | + or – | – | – | + | |
Alcaligenes faecalis |
– | rods | – | – | – | – | – | – | – | + | |
Micrococcus luteus |
+ | cocci in clusters | – | – | – | – | – | – | – | + | |
Staphylococcus epidermidis |
+ | cocci in clusters | F | F | + | – | – | – | – | + | |
Enterococcus faecalis |
+ | cocci in chains | F | F | (+) or – | – | – | – | – | – | |
Lactobacillus plantarum |
+ | rods | F | F | (+) or – | – | – | – | – | – | |
Bacillus sphaericus |
+ | large rods | – | – | – | – | + or – | – | – | + | |
Bacillus cereus |
+ | large rods | F | – | + | – | + or – | – | + | + | |
Bacillus polymyxa |
+ | rods | FG | FG | + | – | + or – | – | + | + |
* For Glucose and Lactose Fermentation Broths: |
A Dichotomous Key which shows one of many ways these organisms can be differentiated from each other is shown here. Links to Keys with Photos: Hopefully you were able to see positive and negative reactions for the various differential media in the lab for Exp. 7 (Period 2). If you did not get to see each of the known cultures that were set up by others in your general area, the results are shown with corresponding photos in the on-line manual here except for two new species (Bacillus sphaericus in place of B. subtilis and Alcaligenes faecalis in place of Chromobacterium violaceum). Dr. Tim Paustian is responsible for this great set of photos and descriptions.
|