In search of a bacterial spedes definition


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Bibliographic Details
Author: Moreno, Edgardo
Format: artículo
Publication Date:1997
Description:The bacterial species concept was examined within the framework of plant and animal associated a-2 proteobacteria, taking into consideration the phylogenetic, taxonomic and biological approaches as well as the microbiologists' perception. The virtue of the phylogenetic approach is that it gi.ves an evolutionary perspective of the bacterial lineage; however the methods used possess low resolution for defining species located at the terminal branches of lhe phylogenetic trees. The merit of the taxonomic that species are defined on the basis of multiple characteristics allowing high resolution at the terminal branches of dendograms; its disadvantage is the inaccuracy in the earliet nodes. Onan individual level, the qualitative biological characteristics used for the definition of species frequently reveal shortcomings because many of these properties are the result of coevolution, parallel evolution or the horizontal transfer of genes. Nevertheless, when considered together with the phylogenetic and taxonomic approaches, important uncertainties are discovered: these must be weighed if a practical definition of bacterial species is conceived. The microbiologi.sts' perception is thecriterion expressed by a group of sponsors who, basedon scientific and practical grounds, propose a new bacterial species. The success of this new .proposal is measured by its widespread acceptance and itspermanence. A difficult pr(jblem con cerned with definingbacterial species is how to distinguish if tbey are independent evolutionary units or if they are reticulate evolutionary units. In the first case the inherenceis vertically transmilted as a result of binary fission and clonal expansiono Thismay be the case of sorne animal ceIl associated bacteria in which recombination appears to be precIuded or exceptional. In the second case adaptive changes occurring within an individual can be horizontally transferred to many or a11 group members. This seems to be the conditión of many intestinal and plant associated bacteria. Genetic drift and speciationin c10nal bacteria will depend a1most .exclusively (jn mutation and intemal genetic rearrangement processes, whereas speciation in reticulate bacteria will depend not only on the processes bút in their genetic interactions wíth other bacterial strains. This uncertainty, wruch corresponds to the evolutionary process, is at the same time one of the key factors in defining a bacterial species
Country:Repositorio UNA
Institution:Universidad Nacional de Costa Rica
Repositorio:Repositorio UNA
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Access Level:acceso abierto