A research project that is only expert-driven may ignore the role of local knowledge in research, give low priority to the development of a comprehensive communication strategy to engage the community, and may not deliver the results of the study to the community in an effective way.
While variable production of the biosurfactant, rhamnolipid, by Pseudomonas aeruginosa has been shown to be dependent on growth conditions, no research has evaluated potential relationships between rhamnolipid production and the presence of heavy metals. The current investigation evaluates the influence of Cd(2+) on rhamnolipid synthesis. Cultures grown in the presence of 0.45 and 0.89 mM Cd(2+) were monitored for rhlB/rhlC expression, rhamnolipid yield, and the ratio of monorhamnolipid (RL1) and dirhamnolipid (RL2) produced. Results show a Cd-induced enhancement of rhlB expression in mid-stationary phase (53 h). In addition, sustained production of rhamnolipid through late stationary growth phase (96 h) was observed for Cd-amended cultures, unlike Cd-free control cultures that ceased rhamnolipid production by mid-stationary growth phase. Most significant was an observed increase in the ratio of RL2 to RL1 congeners produced by cultures grown in the presence of Cd(2+). Previous results have shown that the complexation constant for RL2-Cd is several orders of magnitude larger than that of RL1-Cd thus the preferential production of RL2 in the presence of Cd(2+) impacts its bioavailability and toxicity both for the cell and in the surrounding environment.
Abstract:
Researchers at the University of Arizona have recently determined the structure and studied the properties of a new class of biosurfactants they called flavolipids. Investigation of a partially purified flavolipid mixture isolated from the bacterial culture showed that it was a strong and stable emulsifier, even at a low concentration of 19 mg/L. The mixture exhibited a critical micelle concentration of 300 mg/liter and reduced surface tension to 26.0 mN/m. It was also an effective solubilizing agent. It enhanced biodegradation of hexadecane by two bioremediating bacteria a hundredfold.
Studying co-evolution of hydrological and biogeochemical processes in the subsurface of natural landscapes can enhance the understanding of coupled Earth-system processes. Such knowledge is imperative in improving predictions of hydro-biogeochemical cycles, especially under climate change scenarios. We present an experimental method, designed to capture sub-surface heterogeneity of an initially homogeneous soil system. This method is based on destructive sampling of a soil lysimeter designed to simulate a small-scale hillslope. A weighing lysimeter of one cubic meter capacity was divided into sections (voxels) and was excavated layer-by-layer, with sub samples being collected from each voxel. The excavation procedure was aimed at detecting the incipient heterogeneity of the system by focusing on the spatial assessment of hydrological, geochemical, and microbiological properties of the soil. Representative results of a few physicochemical variables tested show the development of heterogeneity. Additional work to test interactions between hydrological, geochemical, and microbiological signatures is planned to interpret the observed patterns. Our study also demonstrates the possibility of carrying out similar excavations in order to observe and quantify different aspects of soil-development under varying environmental conditions and scale.
