Phylogenetic relationships of bacterial endosymbionts of Paramecium aurelia: polynucleotide sequence relationships of 51 kappa and its mutants

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Abstract
Hydroxyapatite chromatographic procedures were used to investigate the DNA sequence relationships of kappa of P. tetraurelia stock 51 and the organisms that were designated as mutants of 51 kappa. Of the mutants studied, only 51m43 kappa possessed a high percentage (89%) of DNA sequences homologous to those of 51 kappa. All other mutant strains possessed less than 25% polynucleotide sequence homology to 51 kappa DNA. The 3 strains of pi endosymbionts (51m1 pi, 51m43 pi and 139 pi) share greater than 75% DNA sequence homology with each other and approximately 50% DNA sequence homology with 138 mu, the mate-killer endosymbiont found in P. octaurelia. Only 23% of the 51 kappa DNA sequences were homologous with those of 51m1 kappa. Of the mutants studied, only 51m43 kappa could be a mutant of 51 kappa. The pi endosymbionts comprise a closely related group of organisms that are also related to 138 mu but not to any of the kappas tested. The group of organisms designated as kappa appears to be comprised of at least 2 distinct phylogenetic groups.