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An extension of the DLVO-AB model was adapted in an attempt to provide researchers an efficient means of quantifying the interaction of bacterial polymers with solid surfaces. Results revealed that low adherence of bacterial strains tend induce repulsion, while optimal adsorption may lead to surface attraction. It was also found that repulsion may arise as a result of the inability of cells to compress their envelopes, thereby limiting the magnitude of van der Waals force.

Heterogeneity in the adhesion properties within the bacterial populations is a major factor in the large travel distances of bacteria through sand columns. A fraction of the percolated dilute suspensions of Pseudomonas sp. strain B13 deposited in sand columns while the remainder easily passed a second column identical to the first without much hindrance. Increased electrostatic repulsion between sand and bacteria partially reverted the deposition.

An analysis using a generic mathematical concept for bioavailability shows that the mass transfer of a chemical to a microorganism has a greater factor in pollution remediation than the intrinsic biochemical activity of the microorganisms. Such results imply that the pollutants' bioavailability may have been reduced because of their slow mass transfer to the degrading pollutants, providing insights into why the optimization of the activity of microbes by augmentation has not enhanced bioremediation.

A previous study has shown that cell size and cell-solid interactions influence bacterial deposition in coarse grain media. Herein, it is shown that physicochemical factors affect bacterial transport through the clean bed collision efficiency and the area blocked by an attached cell. Analysis of the deposition of seven bacterial strains revealed that cell-cell repulsion enhances blocking and that interactions between the cell and solids are influenced by properties such as cell coating, hydrophobicity of the substratum and the ionic strength of the aqueous phase.

A collision-blocking model was developed to represent deposition of Pseudomonas putida mt2 and Rhodococcus strain C125 during their transport in coarse grain media such a sand columns. Measurements of clean bed collision efficiency and the surface area blocked by attached cells provided evidence showing that cell size and cell-solid interactions influence bacterial deposition.

The enrichment of an anaerobic microbial consortium reductively dechlorinates beta-hexachlorocyclohexane through tetrachlorocyclohexene, resulting in the accumulation of chlorobenzene and benzene. Other important isomers of hexachlorocyclohexane are also dechlorinated to chlorobenzene at similar (alpha) or lower rates (gamma; delta). The addition of vancomycin inhibited dechlorination, but not the addition of bromoethanesulfonic acid. It was, however, completely inhibited by pasteurization.

Hexachloro-1,3-butadiene transformations were studied in columns packed with sediment from the Rhine river and in batch incubations that contain titanium(III) citrate and hydroxocobalamin. Columns were operated under various redox conditions, and transformation was observed in a methanogenic column at influent concentrations of 4 and 400 nmol/L. Hexachloro-1,3-butadiene was reductively dechlorinated to over 90% of (E,E)-1, 2,3,4-tetrachlorobutadiene and less than 5% of trichloro-1,3-butadiene isomer.

Pi movement through Escherichia coli's phosphate inorganic transport system (Pit) is investigated in artificial and natural membranes. The divalent cations present in the bacteria influence the Pi intake through Pit. The movement of metal phosphate complex is transported in solute, which is indicated by the Pi-influenced intake of Mg2+ and Ca2+. The metal phosphate is transported by a mechanistic stoichiometry of 1 along with positively charged hydrogen in symport.

This study quantifies the potential effects of a set of technologies to address water and fertility constraints in rain-fed smallholder agriculture in South Africa, namely in situ water harvesting (WH), external WH, and ecological sanitation (Ecosan, fertilization with human urine). We used the Soil and Water Assessment Tool to model spatiotemporally differentiated effects on maize yield, river flow, evaporation, and transpiration. Ecosan met some of the plant nitrogen demands, which significantly increased maize yields by 12% and transpiration by 2% on average across South Africa. In situ and external WH did not significandy affect the yield, transpiration or river flow on the South Africa scale. However, external WH more than doubled the yields for specific seasons and locations. WH particularly increased the lowest yields. Significant water and nutrient demands remained even with WH and Ecosan management Additional fertility enhancements raised the yield levels but also the yield variability, whereas soil moisture enhancements improved the yield stability. Hence, coupled policies addressing both constraints will likely be most effective for improving food security. [ABSTRACT FROM AUTHOR]

Cereal import has played a crucial role in compensating local water deficit. A quantitative account of water deficit and cereal import relations therefore is of significance for predicting future food import demand and formulating corresponding national and international policies. On the basis of data for countries in Asia and Africa, we estimated a water resources threshold with respect to cereal import. Below the threshold, the demand for cereal import increases exponentially with decreasing water resources. There appeared to be a declining trend in the threshold, from 2000 m3/(capita year) in the early 1980s to 1500 m3/(capita year) by the end of the 1990s. Until recently, most countries below the threshold were oil-rich and thus were able to afford cereal import. However, the next 30 yr may see many poor and populous countries dropping below the threshold in association with their rapid population growth and the depletion of fossil groundwater. Water deficit-induced food insecurity and starvation could intensify because cereal import may not be affordable for these countries.