Tests for Distinguishing from Agrobacterium

Rhizobium and Legume Root Nodulation
Leguminous Plants
The Discovery of Symbiotic Nitrogen Fixation
Rhizobium Classification
Cultural Characteristics
Genetics
Flavonoids Induce Nodualation
Novel Approaches to Extend Root Nodulation
Ecology
Infection
Lectins
Structure of the Nodule
Function of the Nodule
Nitrogenase Hydrogenase Interrelationship
Stem Nodulating Legumes
Factors Affecting Nodulation
Temperature and Light
Hydrogen Ion Concentration
Mineral Nutrition

Tests for Distinguishing from Agrobacterium

	Tests for Distinguishing from Agrobacterium (a) Congo red medium: It has been found that on Congo red incorporated agar medium (2.5 ml of a 1% solution per litre of yeast extract manitol agar), rhizobia stand out as white, translucent, glistening, elevated and comparatively smaller colonies with entire margins in contrast to stained colonies of agrobacteria.
(b) Hofer's alkilline broth: Agrobacteria grow at higher' pH levels, while rhizobia are unable to do so. Therefore, growing bacterial isolates on an alkaline medium (K₂HPO₄, 0.5 g; MgSO₄, 0.2 g; NaCl, 0.1 g; CaCO₃, 0.05 g; yeast extract, 1.0 g; mannitol, 10 g; and water, 1000, ml; pH adjusted to 11.0 by adding approximately 28 ml of N NaOH and 1 ml of 1.6% thymol blue) would serve as a useful criterion for distinguishing the two allied genera. (c) Lactose agar: Agrobacteria utilize lactose to form a reduced product, ketolactose, through the enzyme ketolactase. Benedict's reagent is prepared as follows: 173 g sodium citrate and 100 g anhydrous sodium carbonate are dissolved in 66 ml distilled water; 17.3 g crystalline copper sulphate is dissolved in 100 ml distilled water.
The latter solution is added to the former with constant stirring, the mixture filtered if not clear and made up to 1000 ml with distilled water. The reagent (may be stored indefinitely) is poured over agar medium containing lactose (10 g/litre) on which nodule bacteria are growing. The formation of yellow coloration due to CU₂0 indicates the presence of agrobacteria.

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