Unveiling the role of bioturbation on bacterial activity in metal-contaminated sediments.

The processes permeating the relationships between bioturbation and microorganisms remain poorly understood due to the difficulty of traditional techniques in quantifying their two- and three-dimensional aspects. We used cutting-edge technologies to address the macro- and microorganisms' interactions under metal-contamination. Bioturbation (mucus-lined gallery perimeter, mucus-lined gallery surface area, and gallery water volume) positively influence the carbohydrate consumption rate by the bacterial consortium, elevating bacterial metabolic activity, despite metal-contamination. Synchrotron-based 2D-µXRF revealed that the mucous lining by marine worm during bioturbation as the primary carbon source enhances metal immobilization by bacterial biofilm, improving the bacterial metabolic activity. Bioturbation thus can positively affect bacterial consortium that can use the mucus as a carbon source, which enhances the resistance to metals through biofilm formation in metal-contaminated sediments.

Evaluation of the sensitivity to zinc of ciliates Euplotes vannus and Euplotes crassus and their naturally associated bacteria isolated from a polluted tropical bay.

The aim of this study was to evaluate the Zn sensitivity of Euplotes vannus, Euplotes crassus, and their naturally associated bacteria sampled from sediments in the northwest and east regions of Guanabara Bay. The unexposed ciliates and bacteria did not appear to be negatively affected by 96 h of assay. In the control group, E. vannus exhibited an increase in the biomass content from 2.3 × 10(2) to 2.3 × 10(3) µg C cm(-3) between 0 and 96 h, and E. crassus increased up to 7.07 × 10(2) µg C cm(-3) at 48 h. The maximum biomass was pointed by E. crassus (1.33 × 10(3) µg C cm(-3)) in the presence of 0.005 mg Zn L(-1) and E. vannus was naturally associated bacteria (2.40 × 10(-1) µg C cm(-3)) in the presence of 1.0 mg Zn L(-1) (96 h). The growth of E. vannus from the northwest region showed concentration-dependent manners, and it is more sensitive to zinc than E. crassus from the southeast. Naturally associated bacteria showed better adaptation to increasing concentrations of Zn, and the Dunnett test showed that previous environmental selection is important. These results show that new bioremediation tools are necessary.