The Road to the Taxonomy of Pseudomonas
Norberto J. Palleroni
from: Pseudomonas: Genomics and Molecular Biology (Edited by: Pierre Cornelis). Caister Academic Press, U.K. (2008)
Abstract
As aptly remarked by one of the anonymous reviewers of this opening chapter, the history of the taxonomy of pseudomonads can be qualified as 'tumultuous'. In fact, the addition of this adjective to the title might make it a bit closer to the point. The studies on the taxonomy of this complicated genus groped their way in the dark while following the classical procedures developed for the description and identification of the organisms involved in sanitary bacteriology during the first decades of the twentieth century. This situation sharply changed with the proposal to introduce as the central criterion the similarities in the composition and sequences of macromolecules components of the ribosomal RNA. The new methodology clearly showed that the genus Pseudomonas, as classical defined, consisted in fact of a conglomerate of genera that could clearly be separated into five so-called rRNA homology groups. Moreover, the taxonomic studies suggested an approach that might proved useful in taxonomic studies of all other prokaryotic groups. A few decades after the proposal of the new genus Pseudomonas by Migula in 1894, the accumulation of species names assigned to the genus reached alarming proportions. At the present moment, the number of species in the current list has contracted more than ten-fold. In fact, this approximated reduction may be even more dramatic if one considers that the present list contains many new names, i.e., relatively few names of the original list survived in the process. The new methodology and the inclusion of approaches based on the studies of conservative macromolecules other than rRNA components, constitutes an effective prescription that helped to reduce Pseudomonas nomenclatural hypertrophy to a manageable size. As indicated in the title, the chapter will emphasize a description of the road ('bumps' included) to an acceptable Pseudomonas taxonomy. As remarked by Roger Stanier in his autobiography, the journey itself, not the arrival, matters. Therefore, as a participant in the journey, I apologize for having included only a limited selection of the contributions taken from the enormous flood of information accumulated on this topic in recent years read more ...
