( 1997 )
Phylogenetical relationship based on groE genes among phenotypically related Enterobacter, Pantoea, Klebsiella, Serratia and Erwinia species.
PMID : 12501307 :
In an attempt to define the phylogenetical relationship among 17 phenotypically related species of genera Enterobacter, Pantoea, Serratia, Klebsiella and Erwinia, we determined almost all of their groE operon sequences using the polymerase chain reaction direct sequencing method. The number of nucleotide substitutions per site was 0.12+/-0.030. The value was 3.6-fold higher than that of 16S rDNA. As a result, we were successful in constructing molecular phylogenetic trees which had a finer resolution than that based on the 16S rDNA sequences. The phylogenetic trees based on the nucleotide sequences and deduced amino acid sequences of groE operons indicated that the members of genera Enterobacter, Pantoea and Klebsiella were closely related to each other, while Serratia and Erwinia species except Erwinia carotovora, made distinct clades. The close relationship between Enterobacter aerogenes and Klebsiella pneumoniae, that had been suggested by biochemical tests and DNA hybridization, was also supported by our molecular phylogenetic trees.
( 2002 )
Evolution of the gyrB gene and the molecular phylogeny of Enterobacteriaceae: a model molecule for molecular systematic studies.
PMID : 11931166 : DOI : 10.1099/00207713-52-2-531
Phylogenetic trees showing the evolutionary relatedness of Enterobacteriaceae based upon gyrB and 16S rRNA genes were compared. Congruence among trees of these molecules indicates that the genomes of these species are not completely mosaic and that molecular systematic studies can be carried out. Phylogenetic trees based on gyrB sequences appeared to be more reliable at determining relationships among Serratia species than trees based on 16S rRNA gene sequences. gyrB sequences from Serratia species formed a monophyletic group validated by significant bootstrap values. Serratia fonticola had the most deeply branching gyrB sequence in the Serratia monophyletic group, which was consistent with its atypical phenotypic characteristics. Klebsiella and Enterobacter genera seemed to be polyphyletic, but the branching patterns of gyrB and 16S rRNA gene trees were not congruent. Enterobacter aerogenes was grouped with Klebsiella pneumoniae on the gyrB phylogenetic tree, which supports that this species could be transferred to the Klebsiella genus. Unfortunately, 16S rRNA and gyrB phylogenetic trees gave conflicting evolutionary relationships for Citrobacter freundii because of its unusual gyrB evolutionary process. gyrB lateral gene transfer was suspected for Hafnia alvei. Saturation of gyrB genes was observed by the pairwise comparison of Proteus spp., Providencia alcalifaciens and Morganella morganii sequences. Depending on their level of variability, 16S rRNA gene sequences were useful for describing phylogenetic relationships between distantly related Enterobacteriaceae, whereas gyrB sequence comparison was useful for inferring intra- and some intergeneric relationships.