Title |
Investigation of Candidate Division TM7, a Recently Recognized Major Lineage of the Domain Bacteria with No Known Pure-Culture Representatives
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Published in |
Applied and Environmental Microbiology, January 2001
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DOI | 10.1128/aem.67.1.411-419.2001 |
Pubmed ID | |
Authors |
Philip Hugenholtz, Gene W. Tyson, Richard I. Webb, Ankia M. Wagner, Linda L. Blackall |
Abstract |
A molecular approach was used to investigate a recently described candidate division of the domain Bacteria, TM7, currently known only from environmental 16S ribosomal DNA sequence data. A number of TM7-specific primers and probes were designed and evaluated. Fluorescence in situ hybridization (FISH) of a laboratory scale bioreactor using two independent TM7-specific probes revealed a conspicuous sheathed-filament morphotype, fortuitously enriched in the reactor. Morphologically, the filament matched the description of the Eikelboom morphotype 0041-0675 widely associated with bulking problems in activated-sludge wastewater treatment systems. Transmission electron microscopy of the bioreactor sludge demonstrated that the sheathed-filament morphotype had a typical gram-positive cell envelope ultrastructure. Therefore, TM7 is only the third bacterial lineage recognized to have gram-positive representatives. TM7-specific FISH analysis of two full-scale wastewater treatment plant sludges, including the one used to seed the laboratory scale reactor, indicated the presence of a number of morphotypes, including sheathed filaments. TM7-specific PCR clone libraries prepared from the two full-scale sludges yielded 23 novel TM7 sequences. Three subdivisions could be defined based on these data and publicly available sequences. Environmental sequence data and TM7-specific FISH analysis indicate that members of the TM7 division are present in a variety of terrestrial, aquatic, and clinical habitats. A highly atypical base substitution (Escherichia coli position 912; C to U) for bacterial 16S rRNAs was present in almost all TM7 sequences, suggesting that TM7 bacteria, like Archaea, may be streptomycin resistant at the ribosome level. |
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Denmark | 3 | 1% |
Germany | 2 | <1% |
Netherlands | 1 | <1% |
Canada | 1 | <1% |
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Japan | 1 | <1% |
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Demographic breakdown
Readers by professional status | Count | As % |
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Researcher | 55 | 23% |
Student > Ph. D. Student | 52 | 22% |
Student > Master | 34 | 14% |
Student > Bachelor | 14 | 6% |
Professor > Associate Professor | 10 | 4% |
Other | 36 | 15% |
Unknown | 37 | 16% |
Readers by discipline | Count | As % |
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Environmental Science | 30 | 13% |
Biochemistry, Genetics and Molecular Biology | 20 | 8% |
Immunology and Microbiology | 12 | 5% |
Engineering | 8 | 3% |
Other | 17 | 7% |
Unknown | 50 | 21% |