Using autochthonous Bdellovibrio as a predatory bacterium for reduction of Gram-negative pathogenic bacteria in urban wastewater and reuse it

BACKGROUND AND OBJECTIVES: The microbial contamination of wastewater is associated with health risks. The aim of this study was to use the autochthonous Bdellovibrio potential to prey Gram-negative pathogenic bacteria as a bio-control agent to treat urban wastewater. MATERIALS AND METHODS: Thirty-six raw sewage samples were collected for isolation of Bdellovibrio. Double layer plaque assay was used for isolation and the isolates were identified by microscopic examination and molecular analysis. To evaluate the predatory potential for decrease number of Gram-negative pathogenic bacteria, plaque perdition assay, reduction in host cells viability by colony-forming unit (CFU) counting, reduction in optical density (OD) in co-cultures and assay of killing efficiency were carried out. Also, the raw wastewater was treated by Bdellovibrio then the reduction in CFU counting and reduction in OD was evaluated. RESULTS: Four strains of Bdellovibrio were isolated and were registered in Gene Bank. Clear plaques were observed after 3–6 days of incubation for all prey cells. The CFU enumerations of all preys were decreased after 48 hrs in co-cultures and raw wastewater. Also, OD was decreased down to 0.2 nm after 48 hrs. CONCLUSION: These autochthonous Bdellovibrio strains are proposed to use for bio-control of Gram-negative pathogenic bacteria in wastewater and reuse it for irrigation in arid regions.