Alison D. Searle
February 17, 1997

Isolation and Speciation of The Nitrogen Fixing Bacteria in The Root Nodules Of Pueraria Iobata (Kudzu)

Abstract. Pueraria lobata, commonly known as kudzu, is a perrennial vine that has flourished since it's introduction into the United States in 1876. As a tropical legume, kudzu, grows rapidly in the warm, moist climate of the Southeast. Kudzu, like other legumes, plays an important part in the nitrogen cycle. The mutualistic symbiosis between legumes and nitrogen fixing bacteria, rhizobia, occurs in root nodules. Atmospheric nitrogen is converted to useable forms by the bacteria for the plant. These experiments focused on isolating the bacteria from the root nodules and speciating the bacteria into Rhizobium or Bradyrhizobium genera through microbiological testing. Successful isolation of the rhizobia from the root nodules of kudzu occurred. Positive tests were: rhizobial isolation on YMA with Congo red and Gram staining. Inconclusive tests were: fermentation of sugar broth with alkaline reaction, pH change and formation of serum zone in litmus milk, motility test, and flagella staining. Results from these tests did not contradict the hypothesis that the nitrogen fixing bacteria in kudzu is in the Rhizobium genus; however, further tests should be done before any conclusions can be made. Identifying the bacteria that aid the growth of kudzu may be useful information for possible plant growth control by limiting the nitrogen supply from nitrogen fixation.