ISOLATION AND IDENTIFICATION OF N₂-FIXING ENTEROBACTERIA ASSOCIATED WITH SUGARCANE IN TROPICAL AUSTRALIA

Abstract

The nitrogenase activities of enterobacteria isolated from sugarcane roots and sugarcane waste products were usually 100-400nmol C₂H₄/culture/h. The isolates were characterized both phenotypically and chromosomally. Four phenotypic groups were differentiated. Group 1 isolates were identified as Klebsiella pneumoniae by computer-aided Microbact System 24 E and showed over 70% DNA homology with Klebsiella pneumoniae UQM 90. Isolates of group 3 and group 4 were identified as Enterobacter cloacae and Enterobacter agglomerans respectively by the Microbact 24 E, but DNA-DNA hybridization studies suggested that isolates of these 2 groups belonged to the same species and did not belong to either Enterobacter cloacae or Enterobacter agglomerans. Group 2 isolates were identified as Enterobacter agglomerans by the Microbact 24 E, but G+C% and DNA-DNA hybridization studies contradicted this identification. The G +C% values and phenotypic characteristics indicated that group 2 isolates might represent a new species of the genus Klebsiella while the isolates of group 3 and group 4 together could constitute a new species of the genus Enterobacter.