Summary auto-generated
Researchers isolated an unusual bacterium from a human fetus autopsy in Sweden in 1992, originally misidentified as Shewanella putrefaciens. Using a comprehensive polyphasic approach combining physiological tests, biochemical analysis, fatty acid profiling, and genetic sequencing, scientists determined this bacterium represented an entirely new genus. The organism is a Gram-negative, non-motile rod that grows optimally at 37°C and is facultatively anaerobic, utilizing various electron acceptors including trimethylamine oxide, nitrate, nitrite, and thiosulfate. Its DNA G+C content (50.6 mol%) differed from related Shewanella species. Fatty acid analysis revealed distinctive patterns lacking characteristic Shewanella markers (13:0 iso and 15:0 iso). Phylogenetic analysis of 16S rRNA and gyrB gene sequences showed similarity under 95% to all established genera, with only 71.5% similarity to the closest known species, S. putrefaciens. These findings exceeded conventional thresholds for genus-level distinction. The authors formally named the isolate Alishewanella fetalis gen. nov., sp. nov., with type strain CCUG 30811T, designating it as the first and only characterized member of this new genus.
Key findings
- A novel bacterial genus, Alishewanella fetalis, was identified from a human fetus with unique morphological and biochemical properties distinguishing it from Shewanella and other Proteobacteria
- Fatty acid profiling revealed absence of characteristic Shewanella markers (13:0 iso and 15:0 iso) and elevated levels of 18:1 cis11/trans9/trans6, supporting separate genus status
- 16S rRNA and gyrB gene sequence analysis showed <95% similarity to known genera and <71.5% gyrB similarity to S. putrefaciens, exceeding genus-level divergence thresholds
- The organism is facultatively anaerobic, non-motile, and utilizes multiple electron acceptors (TMAO, nitrate, thiosulfate, nitrite) with optimal growth at 37°C
- Polyphasic taxonomic characterization including physiology, biochemistry, fatty acids, and dual gene sequencing validated creation of a new bacterial genus
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Abstract
A taxonomically unique bacterium is described on the basis of a physiological and biochemical characterization, fatty acid profiling and sequence analyses of 16S rRNA and gyrase B (gyrB) genes. This non-motile, non-fermentative bacterium was isolated from a human foetus in Uppsala, Sweden, and originally misidentified as a Shewanella putrefaciens by conventional biochemical testing. The bacterium grew well at mesophilic temperatures with optimum growth at 37 degrees C. It was facultatively anaerobic and utilized various electron acceptors (trimethylamine oxide, nitrate, nitrite and thiosulphate). The dominant fatty acids were 17:1B, 16:1 cis9, 17:0 and 16:0. Fatty acids 13:0 iso and 15:0 iso, which have been found to be typical of Shewanella species were not detected. The G+C content of the DNA was 50.6 mol%. Phylogenetic analysis of the 16S rRNA gene sequence revealed a clear affiliation with members of the gamma subclass of the Proteobacteria. No relationship was seen with any of the established genera in the gamma subclass of the Proteobacteria, although a distinct relationship with Vibrionaceae was observed. That the bacterium represents a novel bacterial genus distinct from Vibrionaceae was also supported by gyrB sequence analysis. Considering the source and close proximity to the genus Shewanella, the name Alishewanella fetalis gen. nov., sp. nov. is proposed, for which the type strain is strain CCUG 30811(T).