Differential sthA gene expression between filamentous and single-cell forms of Sphaerotilus natans
Résumé
The activated sludge is the most commonly used technology for biological wastewater treatment. Filamentous bacteria are essential component of the activated sludge due to the important roles they play in sludge settleability. Excessive growth of filamentous bacteria, known as bulking, leads to a poor settlement of activated sludge. One of them, Sphaerotilus natans is characterized by a sheathed structure in which long chains of rod-shaped cells are enclosed. S. natans has also been identified in single-cell form as few others filamentous bacteria species isolated from activated sludge. The growth morphology is determined by the environmental conditions. The molecular mechanisms that induce the filamentous growth from a single-cell population are still widely unknown. Nevertheless a gene essential for the filamentous growth and the sheath formation of S. natans has been identified and named sthA. An inactivation of this gene results in sheathless single-cell form growth. In order to find more efficient treatments against bulking the molecular mechanisms of filamentation have to be better known. In this study, the presence of sthA gene was demonstrated as its absence from Leptothrix genome, which is the closest phylogenetic neighbour of S. natans. This gene was sequenced. To analyze the expression of sthA gene in filamentous and single-cell form of S. natans, sthA specific primers useable in RT-QPCR were designed. We have shown that sthA is more expressed in filamentous form than in single cells form. Its expression level is depending of the S. natans strain studied. We have determined that sthA expression increase during filamentous growth.
Origine : Fichiers produits par l'(les) auteur(s)