Isolation and characterization of the catalase gene from Rhizobium sp. SNU003, a root nodule symbiont of Canavalia lineata

A catalase gene from Rhizobium sp. SNU003, a root nodule symbiont of Canava lia lineata, was cloned and its nucleotide sequence was determined. The Rhi zobium DNA of about 280 bp was amplified using two PCR primers synthesized from the conserved sequences of the type I catalase gene. The nucleotide se quence of the amplified fragment revealed three regions that were conserved in the catalase, showing it as being part of the catalase gene. A genomic Southern hybridization using this fragment as a probe showed that the 5.5 k b PstI, 1.8kb EcoRI, and 0.7 kb StyI fragments hybridized strongly with the probe. The Rhizobium genomic Library constructed into the EMBL3 vector was screened, and one catalase clone was selected, The nucleotide sequence of the 5.5 kb PstI fragment from the clone revealed an open reading frame of 1 455 bp, encoding a polypeptide of 485 amino acids with a molecular mass of 54,958 Da and a pi of 6.54, The predicted amino acid sequence of the catala se is 66.3% identical to that of Bacteroides fragilis, but was only 53.3% i dentical to the Rhizobium meliloti catalase.