A study was performed on the biodiversity of actinomycetes in the Gravel Bed Hydroponic (GBH) system constructed wetland for industrial wastewater treatment. Identification of 102 actinomycete isolates recovered from the biofilm of the treatment system revealed high taxonomic diversity. Forty species belonging to ten genera were identified: Streptomyces, Nocardioides, Micromonospora, Nocardiopsis, Nocardia, Actinomadura, Pseudonocardia, Planobispora, Kineosporia and Kitasatospora. The later four genera have never been isolated from biological wastewater treatment systems. The biodiversity of actinomycetes generally increased down the system, where 21 species were recorded at the end of the bed compared to 16 species at its top. Streptomyces and Nocardioides were the most dominant genera in the bed. Numerical analysis of the studied isolates showed a sharp separation of the GBH actinomycete isolates from the corresponding type strains. Actinomycetes from the GBH are suggested to have valuable degradation activities.

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Actinomycete strain TT1-11^T, which produces single non-motile spores on substrate hyphae, was isolated from peat swamp forest soil in Thailand. The isolate showed morphological and chemotaxonomic properties consistent with its classification in the genus Micromonospora. Phylogenetic analysis using 16S rDNA sequences supported this assignment and it formed a subclade with M. coerulea. This isolate can be distinguished from M. coerulea by its physiological and biochemical properties, and it showed a less than 53% DNA relatedness to the type strains of all the validly named Micromonospora species. On the basis of phenotypic, genotypic and phylogenetic data, strain TT1-11^T (=JCM 12357^T =PCU 239^T =DSM 44815^T=TISTR 1232^T) is proposed as the type strain of a novel Micromonospora species, Micromonospora aurantionigra sp. nov.

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An extracellular polysaccharide (EPS) prepared from Rhodococcus rhodochrous ATCC 53968 was found to show high viscosity as a dilute aqueous solution. The reduced viscosity of the dilute aqueous solution of the EPS was 13.9 dl/g, (1.39 m³/kg) representing higher viscosity than that of widely used thickeners such as carboxymethyl cellulose and hydroxyethyl cellulose. The EPS produced by R. rhodochrous ATCC 53968 was found to be an acidic polysaccharide containing galactose, glucose, fucose, and glucuronic acid at a molar ratio of 3: 2: 2: 2. In addition, 1.3% (W/W) stearic acid, 4.1% (W/W) palmitic acid, and 5.8% (W/W) pyruvic acid were also contained in the EPS. These data indicate that this EPS is a novel viscous biopolymer, suggesting the possibility of its application as a thickener.

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