BACTERIAL CHARACTERIZATION OF SEDIMENT AND LAGUNCULARIA RACEMOSA RHIZOSPHERE FROM TRANSECTS OF AN URBAN MANGROVE IN TODOS OS SANTOS BAY (BAHIA STATE, BRAZIL) USING CULTIVATION-DEPENDENT AND -INDEPENDENT METHODS

Raquel Peixoto (IMPPG/UFRJ); Guilherme Chaer (Embrapa); Flávia do Carmo (IMPPG/UFRJ); Fabio Araújo (FFP/UERJ); Jorge Eduardo Paes (Petrobras); Antonia Volpon (Petrobras); Guiomar Alexandra Santiagp (Petrobras); Alexandre Rosado (IMPPG/UFRJ)

Mangroves are coastal ecosystems of extreme ecological and commercial importance, which are threatened with worldwide disappearance. In this study, sediment and rhizosphere samples from nine points of a mangrove with a history of exposure to oil spill, located in Todos os Santos Bay, Brazil, were chemically characterized and had the microbial communities evaluated by conventional and molecular methods. A nearby mangrove site without history of oil spills was also sampled and characterized to serve as a reference. Microbial characterization demonstrated a predominance of hydrocarbon-degrading bacteria in the cultivated strains (about 70%), and clone libraries revealed that Proteobacteria phylum and uncultured bacteria were the dominant members of this community (53 and 21% respectively). Multivariate ordination of DGGE-based microbial community fingerprints exhibited a prevalent separation between sediment and rhizosphere samples for all analyzed bacterial communities (Bacteria, Betaproteobacteria, Alphaproteobacteria, Actinobacteria and Pseudomonas). A Mantel test revealed a significant relationship between both sediment chemical fertility and oil derived pollutants, and most of bacterial community fingerprints from sediment samples, and the counts obtained by nine different cultivation strategies. Among the oil derived pollutants analyzed in sediment samples, total petroleum hydrocarbons (THP) was significantly associated with the Bacteria and Betaproteobacteria fingerprints, while anthracene and total petroleum aromatic hydrocarbon (PAH) were associated with the Actinobacteria. These results suggest that the microbial communities from the studied mangrove reflect the spatial variation of chemical levels present in the sediment. The provided data and the determination of the effects of different pollutants under different microbial groups allows the indication of potential bioindicators to monitor further impacts while also could facilitate further selection of strains with biotechnological potential for application in bioremediation approaches.