Enrichment and Isolation of Rhizobium

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Results

Test/Technique	Result	Interpretation
Streak Plate	white mucilaginous colonies yellow slimy colonies	Two different strains of Rhizobia
Gram Stain	pink rod shaped cells	Gram Negative Bacilli
Capsule Stain	negative	Does not produce capusles but extracellular polysaccharide slime
Catalase Test	positive	Undergoes aerobic respiration
Oxidase Test	white colonies - positive yellow colonies - negative	Further confirms the presence of two different organisms
Wet Mount	yes	Motile organisms
Dextrose Tubes	white colonies - change in color (from red to yellow) yellow colonies - change in color (from red to yellow)	Two different bacterial strins possible
Anaerobic Chamber	white colonies - growth yellow colonies - growth	Inconclusive (Free living Rhizobium cannot grow in anaerobic conditions; the anaerobic chamber was probably not sealed properly)

* white colonies isolated from the soy bean sample
* yellow colonies isolated from the clover sample

Movie: Flagellated motion of Rhizobium from the clover sample.
Click here to download/watch movie.
[AVI file: 3.38Mb]

Rhizobium from the Soybean sample grown on the the YMA plate.	Rhizobium from the clover sample grown on the the YMA plate.
Gram stain of soybean samples showing the gram negative rods.	Gram stain of clover samples showing the gram negative rods.
Capsule stain of the sample showing the extra cellular polysaccharide slime.	Capsule stain of the soybean sample proving that it capsules are not present.
Acid production in the dextrose tubes confirming that the samples are capable of utilizing dextrose.