José Augusto Pires Bitencourt

Protists and bacteria interactions in the presence of oil

Little is known about the role of protists and bacteria interactions during hydrocarbon biodegradation. This work focused on the effect of oil on protists from three different locations in Guanabara Bay and bacteria from Caulerpa racemosa (BCr), Dictyota menstrualis (BDm) and Laurencia obtusa (BLo) during a 96 h bioassay. Cryptomonadida (site 1, 2 and 3), Scuticociliatida (site 2) and Euplotes sp.1 and Euplotes sp.2 (site 3) appeared after incubation. The highest biomass observed in the controls was as follows: protist site 3 (6.0 µgC.cm-3, 96 h) compared to site 3 with oil (0.7 µgC.cm-3, 96 h); for bacteria, 8.6 µgC.cm-3 (BDm, 72 h) and 17.0 µgC.cm-3 (BCr with oil, 24 h). After treatment, the highest biomasses were as follows: protists at site 1 and BLo, 6.0 µgC.cm-3 (96 h), compared to site 1 and BLo with oil, 3.31 µgC.cm-3 (96 h); the bacterial biomass was 43.1 µgC.cm-3 at site 2 and BDm (96 h). At site 3 and BLo with oil, the biomass was 18.21 µgC.cm-3 (48 h). The highest biofilm proportions were observed from BCr 1.7 µm (96 h) and BLo with oil 1.8 µm (24 h). BCr, BLo and BDm enhanced biofilm size and reduced the capacity of protists to prey.

Copper and lead removal from aqueous solutions by bacterial consortia acting as biosorbents.

A bacterial consortium was selected in the presence of Cu from sediment samples taken from Sepetiba Bay, Brazil, which is a site historically contaminated by metals. Bacteria were exposed to 0, 1, 6, 12.5, 25 and 50μg·mL(-1) Cu, Pb and Cu+Pb for 11days of bioassay. Results showed Alcanivorax dominance (81%) and cell counts of 10(8)cells·mL(-1). However, a reduction in dehydrogenase activity was observed from the fifth day of exposure for all Cu, Pb, and Cu+Pb concentrations tested. Esterase activity tended to increase, indicating higher energy demand to complete the bacterial lifecycle. Pb concentrations in the filtered culture medium (0.2μm) were below the detection limit, indicating biosorption, whereas concentrations of Cu were close to the tested concentrations, indicative of efflux. Results suggest the need for biomarkers, such as esterase and dehydrogenase enzymatic activity, in the assessment of resistance and tolerance of communities previously exposed to stressors.

Organic Matter Biodegradation by Bacterial Consortium under Metal Stress

Organic matter biodegradation proceeds via multiple enzymatic reactions, involving different oxidants as well as a number of intermediate compounds. Microbial reworking of organic matter can result in a substantial microbial contribution to the total organic matter pool. The investigations of the mechanisms, which can alter the microbial metabolism in marine sediments, are essential for understanding diagenetic processes, especially at those environments with toxic metal concentrations. Metals can bind with cells components, affecting their functioning. Consequently, the organic matter oxidation in the cellular metabolism may be affected. By contrast, the carbon sources are discriminated between labile and refractory organic compounds. The labile portion of organic matter mainly consists of biopolymers and includes carbohydrates, lipids, and proteins. The aim of this chapter is to present the main results of 10 years of studies regarding the organic matter oxidation by bacterial consortia under toxic metal levels on a tropical estuarine environment surrounded in part by mangrove areas. As the main find, the chronic dominance of lipids and carbohydrates at estuaries and mangroves systems may change the bacterial trophic state from aerobic to anaerobic metabolism. This alteration may reflect on decreasing both bacterial efficiency of organic matter degradation and bacterial productivity. Further, when these systems show high levels of metals at the sediment, the metabolic efficiency is even lower because, although bacteria consortia is able to produce extracellular polymeric substances (EPS) as defense mechanism, multimetal contam‐