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Production of curli, extracellular structures important for biofilm formation, is positively regulated by OmpR, which constitutes with the EnvZ protein an osmolarity-sensing two-component regulatory system. The expression of curli is cryptic in most Escherichia coil laboratory strains such as MG1655, due to the lack of csgD expression. The csgD gene encodes a transcription activator of the curli-subunit-encoding csgBA operon. The ompR234 up-mutation can restore csgD expression, resulting in curli production and increased biofilm formation. In this report, it is shown that ompR234-dependent csgD expression, in addition to csgBA activation during stationary phase of growth, stimulates expression of the yaiC gene and negatively regulates at least two other genes, pepD and yagS. The promoter regions of these four genes share a conserved 11 bp sequence (CGGGKGAKNKA), necessary for csgBA and yaiC regulation by CsgD. While at both the csgBA and yaiC promoters the sequence is located upstream of the promoter elements, in both yagS and pepD it overlaps either the putative--10 sequence or the transcription start point, suggesting that CsgD can function as both an activator and a repressor. Adhesion experiments show that csgD-independent expression of both yagS and pepD from a multicopy plasmid negatively affects biofilm formation, which, in contrast, is stimulated by yaiC expression. Thus it is proposed that CsgD stimulates biofilm formation in E. coli by contemporary activation of adhesion positive determinants (the curli-encoding csg operons and the product of the yaiC gene) and repression of negative effectors such as yagS and pepD.

Taking six southern Mediterranean countries as a case study, this paper addresses the water-food challenges facing water-scarce countries and the implications for the world food economy. By accounting the volume of virtual water embedded in food imports into the countries concerned, a close relationship between water endowment and food import dependence is elaborated. A projection of the cereal demand suggests an increment of 40-60 percentage points in these countries by 2020 above their 1998-99 levels, raising the aggregate volume of cereal imports to around 40 million tons. The analysis also finds that the trend of shifting from staple grain crops to higher-value cash crops was weak during the past two decades. A deteriorating trade deficit for both cereal and noncereal agricultural products was evident in almost all the countries, suggesting a rigid and persistent constraint of water scarcity on overall agricultural development. The results of this case study highlight two important points: (a) food imports are imperative for compensating water resource deficiency; (b) water scarcity-related food imports will continue to expand and impose increasing impacts on the global food economy. Key words--water scarcity, virtual water, food security, food import

Research has been conducted on the bacterial cell binding to the solid surfaces. The ability of the stationary-phase cultures of Escherichia coli W3100 to attach to sand columns grown in Luria broth medium in aerobic conditions has been investigated and the results are reported.

The article compares and contrast watershed management practices of the United States, Brazil, Japan and Switzerland, and the problems inherent in depending on inadequate natural resources and expensive technologies. It is posited that cooperation between resource-rich and resource-poor nations, and between developed and developing nations, will promote sustainable management practices.

An assessment is made of China's water supply, focusing on the inadequacy of policies to conserve water use and draw from new sources. It is suggested that importing grain to relieve the agricultural demand for irrigation is a necessary step in maintaining the nation's water resources.

Research reveals that biofilms may be useful in the protection of steel surfaces from corrosion as indicated by steel electrodes treated with the biofilm-forming bacteria. Data show that unalloyed steel electrodes immersed in the bacterial culture display electrochemical potential activity fluctuations due to vivianite deposition, which suggests bacterial activity.

Research reveals a set of five genes localized to 5.9-kb tfdR-tfdK intergenic region of plasmid pJP4 forming a gene cluster. Data point out that the gene cluster encodes enzymes involved in the conversion of 2,4-dichlorophenol to beta-ketoadipate in Ralstonia eutropha JMP134.

Research has been conducted on the Pseudomonas strains that utilize m-toluate. The results of the isolation of these strains from the oil-contaminated soil samples in Belarus are discussed.

Research has been conducted on the enzyme-based ATP regeneration systems. The use of the Acinetobacter johnsonii polyphosphate:AMP phosphotransferase in the ATP regeneration system is discussed.

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.

A study was undertaken to determine the unknown characteristics of the transmissible chlorocatechol degradation (clc) gene from the Pseudomonas specie strain B13 utilizing pulse-field gel eletrophoresis, DNA-DNA hybridizations and cosmid mapping. The B13 strain was considered a pseudomonad using the 3-chlorobenzoate as the main source of carbon and energy. Results revealed that clc genes were discovered on a transmissible element and the physical appearance of this element was detected by its tandem amplification in the host strain, P. putida F1.

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.

A study was conducted to examine low-frequency horizontal transfers of chlorocatechol degradative genes from Pseudomonas sp. strain B13 in activated-sludge microcosms. Matings were carried out with cultures pre-grown on Luria-Bertani medium that was washed and resuspended in Z3 mineral medium. The microcosms were characterized by glass reactors and operated at a volume of about 05. liter of culture medium.

Ralstonia eutropha is able to grow on 2,4-dichlorophenoxyacetate (2,4-D) as the only source of carbon. The mechanism involved in the uptake of 2,4-D in Ralstonia is investigated by genetic analysis of the pJP4 plasmid. The tfdK gene on this plasmid codes for a product resembling the transport proteins of the major facilitator superfamily. The disruption of this gene reduced 2,4-D assimilation substantially, indicating that it has a role in the uptake of 2,4-D.

An Escherichia coli whole-cell biosensor was developed for linear alkane detection through the transcriptional fusion of Vibrio harveji promotorless luxAB genes and Pseudomonas oleovorans alkB promoter. Standardized and optimized assays were then employed in evaluating the biosensor strain's ability to detect octane concentrations. The biosensor was also found to be useful in estimating linear akane concentrations in groundwater samples contaminated with oil.

A methanogenic microbial consortium which can reductively dechlorinate 1,2,4-trichlorbenzene (1,2,4-TCB) was enriched from a mixture of polluted sediments. Lactate, which was employed as an electron donor during the enrichment, was transformed into methane via proponate and acetate. Hexachlorobenzen and polychlorinated biphenyls were dechlorinated after a lag phase of ca. 15 days, indicating a dechlorination pattern that is different from those for lower chlorinated benzenes. Results indicated that the consortium has at least three distinct dechlorination activities.