Culturable bacteria associated to the rhizosphere and tissues of Iris pseudacorus plants growing in a treatment wetland for winery wastewater discharge

Abstract Winery wastewater is of great concern due to its complex composition, characterized by high organic content and high amounts of readily and slowly biodegradable and recalcitrant compounds. In the present study, the culturable bacteria from rhizo (interstitial water and substrate) and endosphere (inside roots and shoots) of Iris pseudacorus plants inhabiting a treatment wetland mesocosm receiving winery wastewater, were isolated and identified. The innovative approach combined the use of these plants with a substrate based on used cork stoppers, as a support. Of the 53 bacterial isolates retrieved from the rhizo (interstitial water and substrate) and endosphere (root and shoot) of I. pseudacorus plants, the class γ -Proteobacteria was predominant in the shoot and root tissues (72%), but it was also present in the interstitial water and substrate (28%). In total, 13 different genera were found. Pseudomonas and Bacillus were the most represented genera in the rhizosphere while Rahnella and Pseudomonas were dominant in the endosphere of Iris plants. Plant tissues and the water-substrate shared 31% of the genera. Used cork stoppers supported plant growth and can be valorized as substrate in constructed vegetated systems for wastewater treatment and future bioremediation developments may be assisted by the use of resilient bacteria retrieved from such harsh environments.