Legume Root Nodules

The symbiotic nitrogen fixing bacterium from legume nodules. Nitrogen fixation is mediated by two microbial systems: free living microbe like the other symbiotic forms like in the former type. The organisms produce thick walls, there by producing a dormant cyst that is resistant to drying and ultraviolet radiations. The latter type establishes a mutually beneficial association with the plant roots and produces nodules on infected roots.

A root nodule bacterium can be isolated from root nodules of leguminous plants by crushing the nodules and inoculating for hofer's alkaline medium which is specific for its isolation. Hofer's alkaline medium medium has the dye congo red which distinguishes organism cells from some colonies by adsorbing the dye.

Plants having will developed nodules were collected. The large pink nodules were separated from the roots and used for isolation of organism.The microorganisms on the surface of the nodules should be removed by surface sterilization with either 1%mercury chloride or 3-5%hydrogen peroxide were removed by washing the nodules in sterile water for several time. Then the nodules were transformed to the plates containing 70% ethyl alcohol for 3minutes and then washed with sterile water.Then nodules were crashed by using mortar and pestle.The dilution were plated using hofer's alkaline medium. The medium was allow to settle and plates were incubated at room temperature.

Nodules from the root of leguminous plant were collected.The nodules were washed with sterile water.The nodules were placed on a clean slide and crushed by pressing another slide over it. A thin smear was made by sliding the slides one over the other.Smear was allowed to dry and heat fixed.The smear was stained with ethylene blue for 30 seconds.The slides were washed with running water and air dry, the slide was observed for the presence of typical bacteria of various configuration.White,smooth colonies were observed.