Rhizobium meliloti homologs of Escherichia coli mur genes.

The pectate-lyase-encoding gene pelB of Erwinia chrysanthemi Ec16 was used as a probe for hybridization to Rhizobium meliloti Rm1021 chromosomal DNA under low-stringency conditions. An Rm1021 DNA fragment that hybridized to this probe was cloned and sequenced. Results of RNA hybridization indicate that a portion of the cloned fragment is transcribed in R. meliloti. Although the Rm1021 fragment shares no significant nucleotide sequence identity with Ec16 pelB, it includes an ORF (open reading frame) that shares a high degree of nt sequence identity with the Escherichia coli murD gene. This gene codes for UDP-N-acetylmuramoyl-L-alanyl-D-glutamate synthetase, which catalyzes a step in the synthesis of the E. coli cell wall. The R. meliloti putative murD sequence is preceded by a partial ORF that shares sequence identity with mraY. The orientation of the two ORFs in R. meliloti is similar to that of the E. coli murD and mraY genes.