Summary auto-generated
This 1999 study presents a comprehensive polyphasic taxonomy of the genus Shewanella, a group of Gram-negative, rod-shaped bacteria with diverse environmental and clinical significance. The researchers examined phylogenetic relationships among known shewanellae using morphological, physiological, molecular, and chemotaxonomic characterization methods. Key phenotypic markers included sulfur reduction capacity and halophilicity (salt tolerance). Molecular approaches utilized included 16S rDNA sequencing, DNA-DNA hybridization, and gyrB gene analysis, the latter being more discriminatory than 16S rRNA for closely related species. The study characterized twelve Shewanella species total, formally describing Shewanella oneidensis sp. nov. (type strain MR-1), which is notable for its ability to reduce iron and manganese oxides. The researchers also recognized a tentative new species, 'Shewanella pealeana'. An identification scheme for Shewanella species was compiled based on combined phenotypic and molecular data. The study integrated published data, unpublished contributions, and newly generated sequences from multiple institutions to provide a unified classification framework for this metabolically and environmentally important bacterial genus.
Key findings
- Shewanella oneidensis sp. nov. (strain MR-1) is formally described as a new species, particularly notable for its capacity to reduce iron and manganese oxides and for having its complete genome sequenced
- The gyrB gene provides superior resolution compared to 16S rDNA for differentiating closely related Shewanella species, with species-specific PCR probes designed for rapid identification
- Halophilicity (salt tolerance) and sulfur reduction are key phenotypic characteristics that distinguish Shewanella species, with organisms classified as either halotolerant or halophilic based on optimal NaCl concentrations
- Glucose fermentation capability effectively separates S. benthica and S. frigidimarina (glucose-fermenting) from eight other known shewanellae (non-fermenting), enabling practical species differentiation
- Polyphasic taxonomy combining 16S rDNA, gyrB sequencing, DNA-DNA hybridization, fatty acid profiling, and quinone analysis provides comprehensive phylogenetic organization of the genus Shewanella
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Abstract
The genus Shewanella has been studied since 1931 with regard to a variety of topics of relevance to both applied and environmental microbiology. Recent years have seen the introduction of a large number of new Shewanella-like isolates, necessitating a coordinated review of the genus. In this work, the phylogenetic relationships among known shewanellae were examined using a battery of morphological, physiological, molecular and chemotaxonomic characterizations. This polyphasic taxonomy takes into account all available phenotypic and genotypic data and integrates them into a consensus classification. Based on information generated from this study and obtained from the literature, a scheme for the identification of Shewanella species has been compiled. Key phenotypic characteristics were sulfur reduction and halophilicity. Fatty acid and quinone profiling were used to impart an additional layer of information. Molecular characterizations employing small-subunit 16S rDNA sequences were at the limits of resolution for the differentiation of species in some cases. As a result, DNA--DNA hybridization and sequence analyses of a more rapidly evolving molecule (gyrB gene) were performed. Species-specific PCR probes were designed for the gyrB gene and used for the rapid screening of closely related strains. With this polyphasic approach, in addition to the ten described Shewanella species, two new species, Shewanella oneidensis and 'Shewanella pealeana', were recognized; Shewanella oneidensis sp. nov. is described here for the first time.