Biological Instability in a Chlorinated Drinking Water Distribution Network

The purpose of a drinking water distribution system is to deliver drinking water to the consumer, preferably with the same quality as when it left the treatment plant. In this context, the maintenance of good microbiological quality is often referred to as biological stability, and the addition of sufficient chlorine residuals is regarded as one way to achieve this. The full-scale drinking water distribution system of Riga (Latvia) was investigated with respect to biological stability in chlorinated drinking water. Flow cytometric (FCM) intact cell concentrations, intracellular adenosine tri-phosphate (ATP), heterotrophic plate counts and residual chlorine measurements were performed to evaluate the drinking water quality and stability at 49 sampling points throughout the distribution network. Cell viability methods were compared and the importance of extracellular ATP measurements was examined as well. FCM intact cell concentrations varied from 5×10³ cells mL⁻¹ to 4.66×10⁵ cells mL⁻¹ in the network. While this parameter did not exceed 2.1×10⁴ cells mL⁻¹ in the effluent from any water treatment plant, 50% of all the network samples contained more than 1.06×10⁵ cells mL⁻¹. This indisputably demonstrates biological instability in this particular drinking water distribution system, which was ascribed to a loss of disinfectant residuals and concomitant bacterial growth. The study highlights the potential of using cultivation-independent methods for the assessment of chlorinated water samples. In addition, it underlines the complexity of full-scale drinking water distribution systems, and the resulting challenges to establish the causes of biological instability.     

Succinic acid fermentation in a stationary-basket bioreactor with a packed bed of immobilized Actinobacillus succinogenes: 1. Influence of internal diffusion on substrate mass transfer and consumption rate

This paper is dedicated to the study on external and internal mass transfers of glucose for succinic fermentation under substrate and product inhibitions using a bioreactor with a stationary basket bed of immobilized Actinobacillus succinogenes cells. By means of the substrate mass balance for a single particle of biocatalysts, considering the Jerusalimsky kinetic model including both inhibitory effects, specific mathematical expressions have been developed for describing the profiles of the substrate concentrations and mass flows in the outer and inner regions of biocatalyst particles, as well as for estimating the influence of internal diffusion on glucose consumption rate. The results indicated that very low values of internal mass flow could be reached in the particles center. The corresponding region was considered biologically inactive, with its extent varying from 0.24% to 44% from the overall volume of each biocatalyst. By immobilization of bacterial cells and use of a basket bed, the rate of glucose consumption is reduced up to 200 times compared with the succinic fermentation system containing free cells.     

Temperature-dependent intermediates in HIV-1 envelope glycoprotein-mediated fusion revealed by inhibitors that target N- and C-terminal helical regions of HIV-1 gp41

Peptides derived from the N- (N-HR) and C- (C-HR) terminal heptad repeat regions adjacent to the fusion peptide and transmembrane domains, respectively, of human immunodeficiency virus (HIV)-1 gp41 inhibit HIV-1 viral envelope glycoproteins (Env)-mediated cell fusion specifically. The mechanism of HIV-1 Env-mediated cell fusion and its inhibition by agents that target the N- and C-HR regions was investigated. Priming experiments with Env-expressing cells indicate that the N-HR region but not the C-HR region is exposed by treatment with sCD4 at 31 degrees C, whereas both the N- and C-HR regions are exposed at 37 degrees C.     

Improved proteome analysis of Saccharomyces cerevisiae mitochondria by free-flow electrophoresis

The analysis of complex cellular proteomes by means of two-dimensional gel electrophoresis (2-DE) is significantly limited by the power of resolution of this technique. Although subcellular fractionation can be a fundamental first step to increase resolution, it frequently leads to preparations contaminated with other cellular structures. Here, we chose mitochondria of Saccharomyces cerevisiae to demonstrate that an integrated zone-electrophoretic purification step (ZE), with a free-flow electrophoresis device (FFE), can assist in overcoming this problem, while significantly improving their degree of purity. Whereas mitochondrial preparations isolated by means of differential centrifugation include a considerable degree of non-mitochondrial proteins (16%), this contamination could be effectually removed by the inclusion of a ZE-FFE purification step (2%). This higher degree of purity led to the identification of many more proteins from ZE-FFE purified mitochondrial protein extracts (n = 129), compared to mitochondrial protein extracts isolated by differential centrifugation (n = 80). Moreover, a marked decrease of degraded proteins was found in the ZE-FFE purified mitochondrial protein extracts. It is noteworthy that even at a low 2-DE resolution level, a four-fold higher number (17 versus 4) of presumably low abundance proteins could be identified in the ZE-FFE purified mitochondrial protein extracts. Therefore these results represent a feasible approach for an in-depth proteome analysis of mitochondria and possibly other organelles.     

Passive Cutaneous Anaphylaxis with Antigens from Coxiella burneti

Passive cutaneous anaphylaxis (PCA) was produced in guinea pigs sensitized with guinea pig Coxiella burneti phase I–II antiserum and challenged with dimethylsulfoxide- or trichloroacetic acid-soluble extracts from phase I cells. The PCA reaction could not be induced by whole or mechanically disrupted phase I or phase II C. burneti cells or by extracted cells or extracts of phase II cells. The antibody responsible for PCA was in the 7Sγ₁ (fast γ) globulin. Sensitization of the skin by 7Sγ₁ antibody could be blocked nonspecifically by 7Sγ₁ globulin from normal serum or from phase II antiserum. The 7Sγ₂ (slow γ) globulin antibody inhibited the reaction specifically. Some antiserum pools containing high agglutinin and complement-fixing titers to phase I C. burneti cells failed to initiate the PCA reaction, perhaps due to an imbalanced ratio of γ₁ to γ₂ specific globulins or to an imbalance in the ratio of specific to nonspecific γ₁ globulins. Agglutinins to phase I cells were found in both γ₁ and γ₂ antibody globulins. Complement-fixing antibodies were found in the γ₂ globulin fraction.     

Immunoexpression of the relaxin receptor LGR7 in breast and uterine tissues of humans and primates

Background  

The receptor for the peptide hormone relaxin has recently been identified as the heptahelical G-protein coupled receptor, LGR7. In order to generate molecular tools with which to characterize both in vivo and in vitro expression of this receptor in human and primate tissues, specific monotypic antibodies have been generated and applied to a preliminary analysis of human and primate female reproductive tissues.     

Influence of sugar beet breeding on populations of Beta vulgaris ssp. maritima in Italy

Abstract. It is highly probable that transgenic cultivars of sugar beet may influence wild beets in the seed-production-area of northern Italy. For this reason a survey of the local wild beet populations and their habitat characteristics was conducted in 1994/1995, i.e. before transgenic beets and their off spring could have become established. Wild beets (Beta vulgaris ssp. maritima) were found at 21 locations between Trieste and Cesenatico, as part of the natural littoral vegetation classified as Atriplicetum tatarici (Cakiletea maritimae) and Crithmetum (Crithmo-Staticetea). The analysis of phenotypic attributes leads to a division into three different sub-populations. Greenhouse studies on the morphology and life-cycle attributes demonstrated actual gene flow between conventional seed beet and the examined wild beet population.     

High cell density cultivation of recombinant yeasts and bacteria under non-pressurized and pressurized conditions in stirred tank bioreactors

This study demonstrates the applicability of pressurized stirred tank bioreactors for oxygen transfer enhancement in aerobic cultivation processes. The specific power input and the reactor pressure was employed as process variable. As model organism Escherichia coli, Arxula adeninivorans, Saccharomyces cerevisiae and Corynebacterium glutamicum were cultivated to high cell densities. By applying specific power inputs of approx. 48kWm(-3) the oxygen transfer rate of a E. coli culture in the non-pressurized stirred tank bioreactor was lifted up to values of 0.51moll(-1)h(-1). When a reactor pressure up to 10bar was applied, the oxygen transfer rate of a pressurized stirred tank bioreactor was lifted up to values of 0.89moll(-1)h(-1). The non-pressurized stirred tank bioreactor was able to support non-oxygen limited growth of cell densities of more than 40gl(-1) cell dry weight (CDW) of E. coli, whereas the pressurized stirred tank bioreactor was able to support non-oxygen limited growth of cell densities up to 225gl(-1) CDW of A. adeninivorans, 89gl(-1) CDW of S. cerevisiae, 226gl(-1) CDW of C. glutamicum and 110gl(-1) CDW of E. coli. Compared to literature data, some of these cell densities are the highest values ever achieved in high cell density cultivation of microorganisms in stirred tank bioreactors. By comparing the specific power inputs as well as the k(L)a values of both systems, it is demonstrated that only the pressure is a scaleable tool for oxygen transfer enhancement in industrial stirred tank bioreactors. Furthermore, it was shown that increased carbon dioxide partial pressures did not remarkably inhibit the growth of the investigated model organisms.     

Adults' awareness of faces follows newborns' looking preferences

From the first days of life, humans preferentially orient towards upright faces, likely reflecting innate subcortical mechanisms. Here, we show that binocular rivalry can reveal face detection mechanisms in adults that are surprisingly similar to inborn face detection mechanism. We used continuous flash suppression (CFS), a variant of binocular rivalry, to render stimuli invisible at the beginning of each trial and measured the time upright and inverted stimuli needed to overcome such interocular suppression. Critically, specific stimulus properties previously shown to modulate looking preferences in neonates similarly modulated adults' awareness of faces presented during CFS. First, the advantage of upright faces in overcoming CFS was strongly modulated by contrast polarity and direction of illumination. Second, schematic patterns consisting of three dark blobs were suppressed for shorter durations when the arrangement of these blobs respected the face-like configuration of the eyes and the mouth, and this effect was modulated by contrast polarity. No such effects were obtained in a binocular control experiment not involving CFS, suggesting a crucial role for face-sensitive mechanisms operating outside of conscious awareness. These findings indicate that visual awareness of faces in adults is governed by perceptual mechanisms that are sensitive to similar stimulus properties as those modulating newborns' face preferences.