The bacterial species challenge: making sense of genetic and ecological diversity.
ABSTRACT The Bacteria and Archaea are the most genetically diverse superkingdoms of life, and techniques for exploring that diversity are only just becoming widespread. Taxonomists classify these organisms into species in much the same way as they classify eukaryotes, but differences in their biology-including horizontal gene transfer between distantly related taxa and variable rates of homologous recombination-mean that we still do not understand what a bacterial species is. This is not merely a semantic question; evolutionary theory should be able to explain why species exist at all levels of the tree of life, and we need to be able to define species for practical applications in industry, agriculture, and medicine. Recent studies have emphasized the need to combine genetic diversity and distinct ecology in an attempt to define species in a coherent and convincing fashion. The resulting data may help to discriminate among the many theories of prokaryotic species that have been produced to date.
- SourceAvailable from: Martin C J Maiden[show abstract] [hide abstract]
ABSTRACT: An ad hoc committee for the re-evaluation of the species definition in bacteriology met in Gent, Belgium, in February 2002. The committee made various recommendations regarding the species definition in the light of developments in methodologies available to systematists.International journal of systematic and evolutionary microbiology 06/2002; 52(Pt 3):1043-7. · 2.11 Impact Factor
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ABSTRACT: Bacterial systematists face unique challenges when trying to identify ecologically meaningful units of biological diversity. Whereas plant and animal systematists are guided by a theory-based concept of species, microbiologists have yet to agree upon a set of ecological and evolutionary properties that will serve to define a bacterial species. Advances in molecular techniques have given us a glimpse of the tremendous diversity present within the microbial world, but significant work remains to be done in order to understand the ecological and evolutionary dynamics that can account for the origin, maintenance, and distribution of that diversity. We have developed a conceptual framework that uses ecological and evolutionary theory to identify the DNA sequence clusters most likely corresponding to the fundamental units of bacterial diversity. Taking into account diverse models of bacterial evolution, we argue that bacterial systematics should seek to identify ecologically distinct groups with evidence of a history of coexistence, as based on interpretation of sequence clusters. This would establish a theory-based species unit that holds the dynamic properties broadly attributed to species outside of microbiology.Current Biology 06/2007; 17(10):R373-86. · 9.49 Impact Factor
Article: What are bacterial species?[show abstract] [hide abstract]
ABSTRACT: Bacterial systematics has not yet reached a consensus for defining the fundamental unit of biological diversity, the species. The past half-century of bacterial systematics has been characterized by improvements in methods for demarcating species as phenotypic and genetic clusters, but species demarcation has not been guided by a theory-based concept of species. Eukaryote systematists have developed a universal concept of species: A species is a group of organisms whose divergence is capped by a force of cohesion; divergence between different species is irreversible; and different species are ecologically distinct. In the case of bacteria, these universal properties are held not by the named species of systematics but by ecotypes. These are populations of organisms occupying the same ecological niche, whose divergence is purged recurrently by natural selection. These ecotypes can be discovered by several universal sequence-based approaches. These molecular methods suggest that a typical named species contains many ecotypes, each with the universal attributes of species. A named bacterial species is thus more like a genus than a species.Annual Review of Microbiology 02/2002; 56:457-87. · 12.90 Impact Factor