Phylogenetic and physiological characterization of a “Nostocoida limicola”-like organism isolated from activated sludge

Ten strains of “Nostocoida limicola”-like organisms were isolated from a municipal wastewater treatment plant with minor industrial effluent. The near complete 16S rDNA sequences were determined for four strains to analyze the position of the organisms within the phylogenetic tree. All four isolates showed the same 16S rRNA sequence and cluster within the green non sulfur bacteria. Hybridization with oligonucleotide probe AHW183 designed complementarily to diagnostic regions of the 16S rRNA sequences showed a positive reaction with all isolated strains. Hybridization of activated sludge samples with probe AHW183 indicates the filamentous “Nostocoida limicola”-like bacteria commonly to occur inside the sludge flocs and to hardly be detected within the flocs without a specific staining. On HA-medium all strains grow as long coiled, unbranched and unsheathed filaments which usually stain Gram positive and show a variable Neisser reaction. The isolates grow well in liquid HA-medium at COD values between 1 to 4 g O₂ l⁻¹ and a pH range from 6.0–7.8. No growth is detected in liquid R2A-medium and several synthetic mineral salts media containing various carbon and nitrogen sources.