PHYLOGENETIC ANALYSIS OF ERWINIA SPECIES BASED ON 16S RIBOSOMAL-RNA GENE-SEQUENCES

The phylogenetic relationships of the type strains of 16 Erwinia speci es were investigated by performing a comparative analysis of the seque nces of the 16S rRNA genes of these organisms. The sequence data were analyzed by the neighbor-joining method, and each branch was supported by moderate bootstrap values. The phylogenetic tree and sequence anal yses confirmed that the genus Erwinia is composed of species that exhi bit considerable heterogeneity and form four clades that are intermixe d with members of other genera, such as Escherichia coli, Klebsiella p neumoniae, and Serratia marcescens. Cluster I includes the type strain s of Erwinia herbicola, Erwinia milletiae, Erwinia ananas, Erwinia ure dovora, and Erwinia stewartii and corresponds to Dye's herbicola group , Cluster II consists of Erwinia persicinus, Erwinia rhapontici, Erwin ia amylovora, and Erwinia cypripedii. Cluster III consists of Erwinia carotovora subspecies and Erwinia chrysanthemi and is characterized by the production of pectate lyases and cellulases. Erwinia salicis, Erw inia rubrifaciens, and Erwinia nigrifluens form the cluster that is mo st distantly related to other Erwinia species. The data from the seque nce analyses are discussed in the context of biochemical and DNA-DNA h ybridization data.