Analysis of the Phylogenetic Relationships of Strains of Burkholderia solanacearum, Pseudomonas syzygii, and the Blood Disease Bacterium of Banana Based on 16S rRNA Gene Sequences

Abstract

We determined nearly complete 16S rRNA gene sequences for 19 isolates of Burkholderia solanacearum, three isolates of the blood disease bacterium of bananas, and two isolates of Pseudomonas syzygii, the cause of Sumatra disease of cloves. The dendrogram produced by comparing all of these sequences revealed that there were two divisions, which corresponded to the results obtained previously in a restriction fragment length polymorphism analysis (D. Cook, E. Barlow, and L. Sequeira, Mol. Plant Microbe Interact. 2:113-121, 1989) and a total 16S ribosomal DNA (rDNA) sequence analysis of four isolates representing four biovars of B. solanacearum (X. Li, M. Dorsch, T. Del Dot, L. I. Sly, E. Stackebrandt, and A. C. Hayward, J. Appl. Bacteriol. 74:324-329, 1993). Division 1 comprised biovars 3, 4, and 5 and an aberrant biovar 2 isolate (strain ACH0732), and division 2 included biovars 1, 2, and N2, the blood disease bacterium, and P. syzygii. Specific nucleotides at positions 458 to 460 (UUC) and 474 (A) characterized division 2, whereas in division 1 the nucleotides at these positions were ACU and U, respectively. However, strain ACH0732 had a U at position 458, as did division 2 isolates, and G instead of U at position 474. Division 2 consisted of two subdivisions; one subdivision contained two B. solanacearum isolates that originated from Indonesia, P. syzygii strains, and blood disease bacterium strains, and the other subdivision contained all of the other division 2 isolates. Within division 1, the level of 16S rDNA sequence similarity ranged from 99.8 to 100%, and within division 2, the levels of 16S rDNA sequence similarity ranged from 99.1 to 100%. The division 1 isolates exhibited an average level of 16S rDNA sequence similarity to division 2 isolates of 99.3% (range, 99.1 to 99.5%). The occurrence of consistent polymorphisms in the 16S rDNA sequences of B. solanacearum strains, in particular unique 16S rDNA sequence differences in aberrant biovar 2 isolate ACH0732, and the occurrence of the Indonesian subdivision of division 2 suggest that this group is a rapidly evolving (tachytelic) group.