Survival of Escherichia coli in the environment: fundamental and public health aspects

In this review, our current understanding of the species Escherichia coli and its persistence in the open environment is examined. E. coli consists of six different subgroups, which are separable by genomic analyses. Strains within each subgroup occupy various ecological niches, and can be broadly characterized by either commensalistic or different pathogenic behaviour. In relevant cases, genomic islands can be pinpointed that underpin the behaviour. Thus, genomic islands of, on the one hand, broad environmental significance, and, on the other hand, virulence, are highlighted in the context of E. coli survival in its niches. A focus is further placed on experimental studies on the survival of the different types of E. coli in soil, manure and water. Overall, the data suggest that E. coli can persist, for varying periods of time, in such terrestrial and aquatic habitats. In particular, the considerable persistence of the pathogenic E. coli O157:H7 is of importance, as its acid tolerance may be expected to confer a fitness asset in the more acidic environments. In this context, the extent to which E. coli interacts with its human/animal host and the organism''s survivability in natural environments are compared. In addition, the effect of the diversity and community structure of the indigenous microbiota on the fate of invading E. coli populations in the open environment is discussed. Such a relationship is of importance to our knowledge of both public and environmental health.     

Cell surface heparan sulfate proteoglycans from human vascular endothelial cells. Core protein characterization and antithrombin III binding properties.

Human aortic endothelial cells (HAEC) and human umbilical vein endothelial cells (HUVEC) were labeled with 35SO(4)2- for 48 h. The membrane-associated proteoglycans were solubilized from these monolayers with detergent and purified by ion-exchange chromatography on Mono Q, incorporation in liposomes, and gel filtration. The liposome-intercalated proteoglycans were 125I-iodinated and treated with heparitinase before SDS-polyacrylamide gel electrophoresis. Radio-labeled proteins with apparent molecular masses of 130, 60, 46, 35, and 30 kDa (HAEC) and 180, 130, 62, 43, and 35 kDa (HUVEC) were detected by autoradiography. Further characterization by affinity chromatography on immobilized monoclonal antibodies and by Northern blot analysis provided evidence for the expression of syndecan, glypican, and fibroglycan in human endothelial cells. Most of the heparan sulfate which accumulated in the subendothelial matrix was implanted on a 400-kDa core protein. This protein was immunologically related to perlecan and bound to fibronectin. Binding studies on immobilized antithrombin III suggested that all membrane-associated heparan sulfate proteoglycan forms had the capacity to bind to antithrombin III but that high affinity binding was more typical for glypican. Most of the proteoglycans isolated from the extracellular matrix also bound only with low affinity to antithrombin III. These results imply that glypican may specifically contribute to the antithrombotic properties of the vascular wall.     

Comparison of proteins from Mycobacterium fortuitum, Mycobacterium nonchromogenicum and Mycobacterium terrae using flat bed electrophoresis.

Polyacrylamide gel electrophoresis of bacterial lysates in a flat bed gives a linear relationship between 1n mol. wt of the proteins and the square root of their migration distances, thereby allowing standardization of different electrophoresis runs and precise comparison between homologous bands. The results obtained with Mycobacterium fortuitum, M. terrae and M. nonchromogenicum strains were used in numerical analysis. Mycobacterium fortuitum and M. nonchromogenicum showed a greater internal similarity than M. terrae, while two strains of the latter clustered with M. nonchromogenicum. The method described allows the comparison of mycobacteria with different generation times and provides a large number of good characters for numerical taxonomy.     

Preferential expression of cellular retinoic acid binding protein in a subpopulation of neural cells in the developing mouse embryo

The cellular retinoic acid binding protein is thought to be involved in the retinoic-acid-mediated signal transduction pathway. We have isolated the mouse cellular retinoic acid binding protein cDNA from an embryonal-carcinoma-derived cell line by using differential cDNA cloning strategies. In situ hybridization on sections of mouse embryos of various developmental stages indicated that the cellular retinoic acid binding protein gene, which we localized on mouse chromosome 9, is preferentially expressed in a subpopulation of neurectodermal cells. This restricted expression pattern suggests an important role for cellular retinoic acid binding protein in murine neurogenesis.     

X-linked recessively inherited non-specific mental retardation. Report of a large family.

A large kindred is described in which 22 males and 3 females show non-specific mental retardation with impaired speech. An X-linked recessive is the most likely mode of inheritance of this condition. Similar families have been described in the literature, characteristic physical abnormalities are absent and performance I.Q. tends to be higher than verbal I.Q. This possible heterogenous condition may be a major individual cause of mental deficiency in males, and may account for the excess of male retardates in the population.     

Identification of a 64 kDa heparan sulphate proteoglycan core protein from human lung fibroblast plasma membranes with a monoclonal antibody.

Human lung fibroblasts produce heparan sulphate proteoglycans (HSPG) that are associated with the plasma membrane. A monoclonal-antibody (Mab)-secreting hybridoma, S1, was produced by fusion of SP 2/0-AG 14 mouse myeloma cells with spleen cells from mice immunized with partially purified cellular HSPG fractions. The HSPG character of the material carrying the epitope recognized by Mab S1 was demonstrated by: (i) the co-purification of the S1 epitope with the membrane HSPG of human lung fibroblasts; (ii) the decrease in size of the material carrying the S1 epitope upon treatment with heparinase or heparitinase, and the resistance of this material to heparinase treatment after N-desulphation. The S1 epitope appears to be part of the core protein, since it was destroyed by proteinase treatment and by disulphide-bond reduction, but not by treatments that depolymerize the glycosaminoglycan chains and N-linked oligosaccharide chains. Polyacrylamide-gel electrophoresis of non-reduced heparitinase-digested membrane HSPG followed by Western blotting and immunostaining with Mab S1 revealed a single band with apparent molecular mass of 64 kDa. Membrane proteoglycans isolated from detergent extracts or from 4 M-guanidinium chloride extracts of the cells yielded similar results. Additional digestion with N-glycanase lowered the apparent molecular mass of the immunoreactive material to 56 kDa, suggesting that the core protein also carries N-linked oligosaccharides. Fractionation of 125I-labelled membrane HSPG by immuno-affinity chromatography on immobilized Mab S1, followed by heparitinase digestion and polyacrylamide-gel electrophoresis of the bound material, yielded a single labelled band with apparent molecular mass 64 kDa. Treatment with dithiothreitol caused a slight increase in apparent molecular mass, suggesting that the core protein of this membrane proteoglycan of a single subunit containing (an) intrachain disulphide bond(s).     

Heparan sulfate proteoglycans of human lung fibroblasts. Structural heterogeneity of the core proteins of the hydrophobic cell-associated forms

Heparan sulfate proteoglycans (HSPG) were solubilized from human lung fibroblast monolayers with detergent. Presumptive membrane-associated forms displaying hydrophobic properties were purified by gel filtration on Sepharose CL-4B, by ion-exchange chromatography on Mono Q and by incorporation in lipid vesicles. The HSPG preparations were 125I-iodinated and treated with heparitinase before sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Five radiolabeled proteins with apparent molecular weights of 125,000, 90,000, 64,000, 48,000, and 35,000 were visualized by autoradiography. A sixth protein, identified in nonreduced 125I-HSPG preparations, appeared as a non-HS chain-bearing Mr 35,000 peptide which was disulfide-linked to an HS chain-bearing peptide of similar size. This multiplicity of core proteins did not seem to result from proteolysis during the heparitinase treatment itself, since some of the core proteins migrated independently during gel filtration before heparitinase digestion. Moreover, heparitinase digestion of 125I-HSPG purified by affinity chromatography on an immobilized monoclonal antibody yielded only the Mr 64,000 protein. Alternative depolymerizations of the HS chains by heparinase or HNO2 also yielded multiple protein bands. These results imply that heterogeneity of the core protein moiety may be a genuine property of the hydrophobic HSPG of human lung fibroblasts. The occurrence of multiple integral membrane HSPG forms may be relevant for the multiple functions that have been ascribed to cell-surface HSPG.