Bacterial community dynamic associated with autochthonous bioaugmentation for enhanced Cu phytoremediation of salt-marsh sediments

Autochthonous bioaugmentation for metal phytoremediation is still little explored, particularly its application to estuarine salt marshes, but results obtained so far are promising. Nevertheless, understanding the behaviour of the microbial communities in the process of bioaugmentation and their role in improving metal phytoremediation is very important to fully validate the application of this biological technology. This study aimed to characterize the bacterial community dynamic associated with the application of autochthonous bioaugmentation in an experimentation which showed that Phragmites australis rhizosphere microorganisms could increase this salt marsh plant potential to phytoremediate Cu contaminated sediments. Bacterial communities present in the autochthonous microbial consortium resistant to Cu added to the medium and in the sediment at the beginning and at the end of the experiment were characterized by ARISA. Complementarily, the consortium and the sediment used for its production were characterized by next generation sequencing using the pyrosequencing platform 454. The microbial consortium resistant to Cu obtained from non-vegetated sediment was dominated by the genus Lactococcus (46%), Raoultella (25%), Bacillus (12%) and Acinetobacter (11%), whereas the one obtained form rhizosediment was dominated by the genus Gluconacetobacter (77%), Bacillus (17%) and Dyella (3%). Results clearly showed that, after two months of experiment, Cu caused a shift in the bacterial community structure of sediments, an effect that was observed either with or without addition of the metal resistant microbial consortium. Therefore, bioaugmentation application improved the process of phytoremediation (metal translocation by the plant was increased) without inducing long term changes in the bacterial community structure of the sediments. So, phytoremediation combined with autochthonous bioaugmentation can be a suitable technology for the recovery of estuarine areas, contributing for an efficient risk management strategy of these coastal zones. © 2017

To Rayra Santiago, Tatiana Necrasov and Catarina Magalhães for their help in the experiments assembling and dismantling of the vessels and to Paula Rodrigues for helping on samples preparation and metal analysis. This research was partially supported by the Strategic Funding UID/Multi/04423/2013 through national funds provided by FCT – Foundation for Science and Technology and European Regional Development Fund (ERDF) , in the framework of the programme PT2020 and by the structured Program of R&D&I INNOVMAR - Innovation and Sustainability in the Management and Exploitation of Marine Resources , reference NORTE-01-0145-FEDER-000035 , namely within the Research Line ECOSERVICES (Assessing the environmental quality, vulnerability and risks for the sustainable management of the NW coast natural resources and ecosystem services in a changing world) within the R&D Institution CIIMAR (Interdisciplinary Centre of Marine and Environmental Research), supported by the Northern Regional Operational Programme ( NORTE2020 ), through the European Regional Development Fund (ERDF) .