McKenzie Primerano and Calvin Young
BSCI 223H Section 0101

Introduction
      
    Rhizobium is a genus of gram negative bacteria that can fixate atmospheric nitrogen into forms that can be used by plants, such as ammonium and nitrate.  The bacteria are able to establish a symbiotic relationship with host legumes (Leguminosae).  They do this by invading the root hairs of young plants, inducing the formation of root nodules.  Different species of Rhizobium exhibit specificity towards certain legumes.  The bacteria are pleomorphic, and motile by means of flagella.  Rhizobium undergo aerobic respiration using oxygen as the terminal electron acceptor.  The optimal growing temperature is 25 to 30 degrees Celsius.  When isolated in the laboratory, the colonies can be described as circular, convex, opaque, and mucilagenous, and will grow in 3 to 5 days on Yeast Mannitol Agar.                                      

Hypothesis                                                     
    The protocol will result in the successful isolation of Rhizobium from Trifolium repens root nodules (white clover). This will be accomplished using an enrichment culture which is defined as the "use of selective culture media and incubation conditions to isolate microorganisms directly from nature" according to Thomas Brock in the textbook Brock, Biology of Microorganisms. The protocol will be successful because only one organism exists within the root nodule once it is formed. The procedure will eliminate all other possible microorganisms.