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- Title
Identification and characterization of the S-layer formed on the sheath of Thiothrix nivea.
- Authors
Kawasaki, Yuta; Kurosaki, Kaishi; Kan, Daisuke; Borges, Isabele Kazahaya; Atagui, Ayumi Satake; Sato, Michio; Kondo, Keiko; Katahira, Masato; Suzuki, Ichiro; Takeda, Minoru
- Abstract
Thiothrix nivea is a filamentous sulfur-oxidizing bacterium common in activated sludge and its filament is covered with a polysaccharide layer called sheath. In this study, we found that T. nivea aggregates under acidic conditions. A hexagonal lattice pattern, a typical morphological feature of proteinaceous S-layers, was newly observed on the surface of the sheath by transmission electron microscopy. The pattern and the acid-dependent aggregation were not observed in T. fructosivorans, a relative sheath-forming bacterium of T. nivea. The putative S-layer of T. nivea was detached by washing with unbuffered tris(hydroxymethyl)aminomethane base (Tris) solution and a protein of 160 kDa was detected by electrophoresis. Based on partial amino acid sequences of the protein, its structural gene was identified. The gene encodes an acidic protein which has a putative secretion signal and a Ca2+-binding domain. The protein was solubilized with urea followed by dialysis in the presence of calcium. A hexagonal lattice pattern was observed in the aggregates formed during dialysis, revealing that the protein is responsible for S-layer formation. Biosorption ability of copper, zinc, and cadmium onto the T. nivea filament decreased upon pretreatment with Tris, demonstrating that the S-layer was involved in metal adsorption. Moreover, aggregation of Escherichia coli was promoted by acidification in the presence of the S-layer protein, suggesting that the protein is potentially applicable as an acid-driven flocculant for other bacteria.
- Subjects
SULFUR bacteria; POLYSACCHARIDES; TRANSMISSION electron microscopy; HYDROXYMETHYL compounds; FLOCCULANTS
- Publication
Archives of Microbiology, 2018, Vol 200, Issue 8, p1257
- ISSN
0302-8933
- Publication type
Article
- DOI
10.1007/s00203-018-1543-x