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High concentrations of metals in the environment alter bacterial diversity, selecting resistant and tolerant species. The study evaluated the selection of a potential bacterial strain from Sepetiba Bay-Rio de Janeiro, Brazil marine sediments to remove Cu and Pb. The bacterial strain isolated from the sediments was used in three different bioassays: (1) Cu at concentrations of 0 (control), 6 and 50 μg.mL -1 ; (2) Pb at concentrations of 0 (control), 6 and 50 μg.mL -1 ; (3) Cu + Pb in concentrations of 3 μg.mL -1 Cu + 3 μg.mL -1 Pb (6 μg.mL -1 ) and 25 μg.mL -1 Cu + 25 μg.mL -1 Pb (50 μg.mL -1 ). The number of cells and the enzymatic activities of dehydrogenases and esterases were quantified. Results of taxonomic identification indicated the selection of the Pseudomonas stutzeri W228 strain, showing a greater degree of similarity (±73%) with the database used. There was no significant variation in the number of cells, 10 8 cells.mL -1 , which represents a high biomass production in the presence of stressors. However, we observed a reduction in dehydrogenase activity at all tested concentrations of Cu, Pb and Cu + Pb. The activity of esterase increased, indicating a higher energy demand to complete the bacterial life cycle. The study showed significant results for the absorption of Pb by the extracellular polymeric substances (EPS) and the efflux of Cu. The capacity of Pb absorption by EPS can be considered a resistance mechanism, as well as the efflux of Cu, so that the available EPS sites could be occupied by the most toxic ions demonstrating that Pseudomonas stutzeri is resistant to Pb and Cu.

ABSTRACT. The aim of this work was to investigate the effect of marine diesel oil on the development and survival of three different species of mangrove propagules with or without a hydrocarbon-degrading bacterial consortium and the possible use of propagules for the recovery of mangroves impacted by oil. The study was conducted in a greenhouse, near a mangrove from which we collected samples of sediments and propagules of Laguncularia racemosa, Avicennia schaueriana and Rhizophora mangle. The bacterial consortium comprised Bacillus spp., Rhizobium spp., Pseudomonas spp., Ochrobactrum spp. and Brevundimonas spp. After six months, L. racemosa and A. schaueriana only survived in control treatments and R. mangle showed the highest survival rates of the three species, indicating that different mangrove species do not respond uniformly to oil spills. Propagules of R. mangle are much more resistant and the hydrocarbon-degrading bacterial consortium we tested can be applied in the phytoremediation of pollutants.

Marine environments are a repository for metals, and humans have enhanced this phenomenon over the years. Heavy metals are notoriously toxic due to their ability to biomagnify in the food chain and interact with cellular components. Nevertheless, some bacteria have physiological mechanisms that enable them to survive in impacted environments. This characteristic makes them important as biotechnological tools for environmental remediation. Thus, we isolated a bacterial consortium in Guanabara Bay (Brazil), a place with a long metal pollution history. To test the growth efficiency of this consortium in Cu–Zn-Pb-Ni–Cd medium, we measured the activity of key enzymes of microbial activity (esterases and dehydrogenase) under acidic (4.0) and neutral pH conditions, as well as the number of living cells, biopolymer production, and changes in microbial composition during metal exposure. Additionally, we calculated the predicted physiology based on microbial taxonomy. During the assay, a slight modification in bacterial composition was observed, with low abundance changes and little production of carbohydrates. Oceanobacilluschironomi, Halolactibacillus miurensis, and Alkaliphilus oremlandii were predominant in pH 7, despite O. chironomi and Tissierella creatinophila in pH 4, and T. creatinophila in Cu–Zn-Pb-Ni–Cd treatment. The metabolism represented by esterases and dehydrogenase enzymes suggested bacterial investment in esterases to capture nutrients and meet the energy demand in an environment with metal stress. Their metabolism potentially shifted to chemoheterotrophy and recycling nitrogenous compounds. Moreover, concomitantly, bacteria produced more lipids and proteins, suggesting extracellular polymeric substance production and growth in a metal-stressed environment. The isolated consortium showed promise for bioremediation of multimetal contamination and could be a valuable tool in future bioremediation programs.