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1 Section of Environmental Engineering, Aalborg University, Sohngaardsholmsvej 57, DK-9000 Aalborg, Denmark
2 Advanced Wastewater Management Centre, School of Molecular and Microbial Sciences, The University of Queensland, St Lucia, Queensland 4072, Australia
Correspondence
Per H. Nielsen
phn{at}bio.aau.dk
An industrial wastewater treatment plant at Grindsted, Denmark, has suffered from bulking problems for several years caused by filamentous bacteria. Five strains were isolated from the sludge by micromanipulation. Phylogenetic analysis of the 16S rRNA gene sequences showed that the strains formed a monophyletic cluster in the Alphaproteobacteria, and they were phenotypically different from their closest relatives and from all hitherto known filamentous bacteria described (closest relative Brevundimonas vesicularis ATCC 11426T, 89.8 % sequence similarity). In pure culture, the cells (1.5–2.0 µm) in filaments are Gram-negative and contain polyphosphate and polyhydroxyalkanoates. The optimum temperature for growth is 30 °C and the strains grow in 2 % NaCl and are oxidase- and catalase-positive. Ubiquinone 10 is the major quinone. The major fatty acid (C18 : 1
7c) and smaller amounts of unsaturated fatty acids, 3-hydroxy fatty acids with a chain length of 16 and 18 carbon atoms and small amounts of 10-methyl-branched fatty acids with 18 carbon atoms (C19 : 0 10-methyl) affiliated the strains with the Methylobacterium/Xanthobacter group in the Alphaproteobacteria. The G+C content of the DNA is 42.9 mol% (for strain Gr1T). The two most dissimilar isolates by 16S rRNA gene comparison (Gr1T and Gr10; 97.7 % identical) showed 71.5 % DNA–DNA relatedness. Oligonucleotide probes specific for the pure cultures were designed for fluorescence in situ hybridization and demonstrated that two filamentous morphotypes were present in the Grindsted wastewater treatment plant. It is proposed that the isolates represent a new genus and species, Meganema perideroedes gen. nov., sp. nov. The type strain of Meganema perideroedes is strain Gr1T (=DSM 15528T=ATCC BAA-740T).
-hydroxybutyrate; WWTP, wastewater treatment plantThe GenBank/EMBL/DDBJ accession numbers for the 16S rRNA gene sequences of strains Gr1T, Gr2, Gr5, Gr10 and Gr28 are AF180468 and AY170117–AY170120.
Interstrain 16S rRNA gene sequence similarities, confocal laser scanning micrographs of FISH of activated sludge from Grindsted WWTP and a phase-contrast micrograph of filaments of strain Gr1T are available as supplementary material in IJSEM Online.
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 C. Kragelund, Y. Kong, J. van der Waarde, K. Thelen, D. Eikelboom, V. Tandoi, T. R. Thomsen, and P. H. Nielsen Ecophysiology of different filamentous Alphaproteobacteria in industrial wastewater treatment plants. Microbiology, October 1, 2006; 152(Pt 10): 3003 - 3012. [Abstract] [Full Text] [PDF]
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