Search

Molecular crystals with water molecules in the crystal lattice (hydrates) can radically change properties if dehydrated. The two most practically relevant pathways of dehydration can be classified as either thermally-induced or solvent-induced. The solid form transformations occurring during these processes are taking place at the surface of the particles either in the solid–gas or solid–liquid interface. In this study, it is demonstrated how atomic force microscopy (AFM) can be used to measure topography, elastic modulus and work function to elucidate differences at the crystal surface depending on the dehydration pathway. These results are performed at a single particle level, so it would be important to link the findings to the bulk powder behaviour. To address this, static charging measurements for bulk powder samples were compared with the single crystal surface measurements. The thermally-induced anhydrate acquired more charge than the monohydrate at the bulk level which could be explained by the increase in work function and surface roughness at a single particle level. The change in sign for the solvent-induced anhydrate was also in agreement with the work function. This underpins the importance of also considering microscale properties, when characterizing nanoscale structures at the surface of particulate systems. [ABSTRACT FROM AUTHOR]

To show that an adsorbing biofilm carrier (GAC) can be advantageous for atrazine bioremediation over a non-adsorbing carrier, fluidized bed (FB) reactors were operated under atrazine limiting concentrations using Pseudomonas sp. strain ADP as the atrazine degrading bacteria. The following interrelated subjects were investigated: 1) atrazine adsorption to GAC under conditions of atrazine partial penetration in the biofilm, 2) differences in atrazine degradation rates and 3) stability of atrazine biodegradation under non-sterile anoxic conditions in the GAC reactor versus a reactor with a nonadsorbing biofilm carrier. Results from batch adsorption tests together with modeling best described the biofilm as patchy in nature with covered and non-biofilm covered areas. Under conditions of atrazine partial penetration in the biofilm, atrazine adsorption occurs in the non-covered areas and is consequently desorbed at the base of the biofilm substantially increasing the active biofilm surface area. The double flux of atrazine to the biofilm in the GAC reactor results in lower effluent atrazine concentrations as compared to a FB reactor with a non-adsorbing carrier. Moreover, under non-sterile denitrification conditions, atrazine degradation stability was found to be much higher (several months) using GAC as a biofilm carrier while non-adsorbing carrier reactors showed sharp deterioration within 30 days due to contamination of non-atrazine degrading bacteria. [ABSTRACT FROM AUTHOR]

To show that an adsorbing biofilm carrier (GAC) can be advantageous for atrazine bioremediation over a non-adsorbing carrier, fluidized bed (FB) reactors were operated under atrazine limiting concentrations using Pseudomonas sp. strain ADP as the atrazine degrading bacteria. The following interrelated subjects were investigated: 1) atrazine adsorption to GAC under conditions of atrazine partial penetration in the biofilm, 2) differences in atrazine degradation rates and 3) stability of atrazine biodegradation under non-sterile anoxic conditions in the GAC reactor versus a reactor with a non-adsorbing biofilm carrier. Results from batch adsorption tests together with modeling best described the biofilm as patchy in nature with covered and non-biofilm covered areas. Under conditions of atrazine partial penetration in the biofilm, atrazine adsorption occurs in the non-covered areas and is consequently desorbed at the base of the biofilm substantially increasing the active biofilm surface area. The double flux of atrazine to the biofilm in the GAC reactor results in lower effluent atrazine concentrations as compared to a FB reactor with a non-adsorbing carrier. Moreover, under non-sterile denitrification conditions, atrazine degradation stability was found to be much higher (several months) using GAC as a biofilm carrier while non-adsorbing carrier reactors showed sharp deterioration within 30 days due to contamination of non-atrazine degrading bacteria. [ABSTRACT FROM AUTHOR]

The reticulocyte cell membrane was investigated for the role that it plays in cellular protein synthesis. It was found that a strong inhibition in protein synthesis occurred when a membranal extract was added to a cell-free protein-synthesizingsystem. The membranal extract was obtained by disrupting and then solubilizing cell membranes with the non-ionic detergent Triton X-100. The inhibition in protein synthesis could neither be attributed to an RNAse-type action nor to a reduction in the energy level of the system. Preliminary results show that the principal site of action occurs at the elongation or/and termination stages of protein synthesis. Initial purification of the inhibitory component was achieved. [ABSTRACT FROM AUTHOR]

During maturation of reticulocytes their ribosomes become less active for protein synthesis. Testing the stimulation effect of KCl ribosomal wash (KCl factors) extracted from ribosomes from cells oK different ages isolated by "density distribution of cells" technique, we show that active KCl factors are present on ribosomes from young cells and not on ribosomes from old cells. We demonstrate that the KCl factors can form polysomes from monosomes. The level of action of these factors is investigated and the possibility that they act as initiation factors is examined. [ABSTRACT FROM AUTHOR]

Aims The aim of this study was to engineer Escherichia coli strains that efficiently produce succinate from glycerol under anaerobic conditions after an aerobic growth phase. Methods and Results We constructed E. coli strain ss195 with deletions of pyk A and pyk F, which resulted in slow growth on glycerol as sole carbon source. This growth defect was overcome by the selection of fast-growing mutants. Whole-genome resequencing of the evolved mutant ss251 identified the mutation A595S in PEP carboxylase ( Ppc). Reverse metabolic engineering by introducing the wild-type allele revealed that this mutation is crucial for the described phenotype. Strain ss251 and derivatives thereof produced succinate with high yields above 80% mol mol−1 from glycerol under nongrowth conditions. Conclusions The results show that during the aerobic growth of ss251, the formation of pyruvate proceeds via the proposed POMP pathway, starting with the carboxylation of PEP by Ppc. The resulting oxaloacetate is reduced by malate dehydrogenase ( Mdh) to malate, which is then decarboxylated back to pyruvate by a malic enzyme ( Mae A or Mae B). Mutation of ppc is crucial for fast growth of pyk AF mutants on glycerol. Significance and Impact of Study An E. coli mutant that is capable of achieving high yields of succinate (a top valued-added chemical) from glycerol (an abundant carbon source) was constructed. The identified ppc mutation could be applied to other production strains that require strong PEP carboxylation fluxes. [ABSTRACT FROM AUTHOR]

Purified IgM and IgG anti-Salmonella typhimurium 'O' antibodies were isolated at various intervals during the primary and secondary immune responses. Using agglutination, complement-dependent bactericidal effect and passive inhibition of antibody formation assays, the specific activities of IgM antibodies were found to be higher than IgG antibodies isolated at the same interval. As the immune response developed, a progressive increase in the specific secondary biological activities of both immunoglobulins was detected. In selected experiments, antibodies of a single immunoglobulin class were further fractionated into populations of molecules of different activity. An indirect assay of 'avidity' indicated that there was a direct relationship between this measure of antigen-antibody interaction and the secondary biological properties of these immunoglobulins. [ABSTRACT FROM AUTHOR]

• Stormwater biofiltration system targeting atrazine removal was developed. • Introduction of GAC enhanced proliferation of micropollutant-degrading bacteria. • Full atrazine removal was recorded, significantly beyond the GAC adsorption capacity. • Kinetics of t rzN gene abundance was accelerated on GAC vs. sand (0.8 vs. 0.37 week−1). • Consistent removal of other typical stormwater macropollutants. Waters contaminated with micropollutants are of environmental and public health concern globally. Stormwater is a significant source of anthropogenic micropollutants to receiving waters. Hence, sustainable stormwater remediation is needed to reduce contamination of waterways. Yet designing sustainable bioremediation solutions, including those targeted to remove micropollutants, is a major scientific challenge. This study aimed to adapt the design of stormwater biofiltration systems, to improve the removal of micropollutants and understand the role of the micropollutant-degrading bacteria in this bioremediation process. We investigated the atrazine removal performance of a prototype biofiltration system, in which the filter media was supplemented with Granulated Activated Carbon (GAC). The prototype biofiltration system completely removed atrazine to below detectable limits, significantly exceeding the GAC's adsorption capacity alone, suggesting other biological processes were present. We showed that atrazine degradation capacity, measured by the kinetics of the trzN gene abundance, was accelerated in the prototype system compared to the standard system (which had no added GAC; 0.8 vs. 0.37 week−1, respectively). Notably, this high level of atrazine removal did not come at the expense of the removal performance of other typical stormwater macropollutants (e.g., nutrients, suspended solids). The prototype biofiltration system showed a proof-of-concept of sustaining microbial remediation of a model micropollutant alongside stormwater macropollutants, which could be used to reduce impacts on receiving waterways and protect our ecosystems and human health. [Display omitted]. [ABSTRACT FROM AUTHOR]

Previously, we reported that epithelial cells respond to exogenous interleukin (IL)-1α by increasing expression of several genes involved in the host response to microbes, including the antimicrobial protein complex calprotectin (S100A8/A9). Given that S100A8/A9 protects epithelial cells against invading bacteria, we studied whether IL-1α augments S100A8/A9-dependent resistance to bacterial invasion of oral keratinocytes. When inoculated with Listeria monocytogenes, human buccal epithelial (TR146) cells expressed and released IL-1α. Subsequently, IL-1α-containing media from Listeria-infected cells increased S100A8/A9 gene expression in naïve TR146 cells an IL-1 receptor (IL-1R)-dependent manner. Incubation with exogenous IL-1α decreased Listeria invasion into TR146 cells, whereas invasion increased with IL-1R antagonist. Conversely, when S100A8/A9 genes were knocked down using short hairpin RNA (shRNA), TR146 cells responded to exogenous IL-1α with increased intracellular bacteria. These data strongly suggest that infected epithelial cells release IL-1α to signal neighboring keratinocytes in a paracrine manner, promoting S100A8/A9-dependent resistance to invasive L. monocytogenes. [ABSTRACT FROM AUTHOR]

Methionine sulphoxide reductase maintains adhesin function during oxidative stress. Using Streptococcus gordonii as a model, we now show the mechanistic basis of adhesin maintenance provided by MsrA. In biofilms, S. gordonii selectively expresses the msrA gene. When the wild-type strain was grown with exogenous hydrogen peroxide (HO), msrA-specific mRNA expression significantly increased, while acid production was unaffected. In the presence of HO, a msrA-deletion mutant (ΔMsrA) showed a 6 h delay in lag phase growth, a 30% lower yield of HO, significantly greater inhibition by HO on agar plates (reversed by complementation), 30% less adhesion to saliva-coated hydroxyapatite, 87% less biofilm formation and an altered electrophoretic pattern of SspAB protein adhesins. Using mass spectrometry, methionine residues in the Met-rich central region of SspB were shown to be oxidized by HO and reduced by MsrA. In intact wild-type cells, MsrA colocalized with a cell wall-staining dye, and MsrA was detected in both cell wall and cytosolic fractions. To maintain normal adhesion and biofilm function of S. gordonii in response to exogenous oxidants therefore msrA is upregulated, methionine oxidation of adhesins and perhaps other proteins is reversed, and adhesion and biofilm formation is maintained. [ABSTRACT FROM AUTHOR]

Expressed by squamous mucosal keratinocytes, calprotectin is a complex of two EF-hand calcium-binding proteins of the S100 subfamily (S100A8 and S100A9) with significant antimicrobial activity. Calprotectin-expressing cells resist invasion by Porphyromonas gingivalis, Listeria monocytogenes, and Salmonella enterica serovar Typhimurium (S. typhimurium). To understand the interactions between calprotectin and invasive bacteria, we studied the distribution of calprotectin in the cytoplasm of TR146 epithelial cells. In response to L. monocytogenes, calprotectin mobilized from a diffuse cytoplasmic distribution to a filamentous pattern and colocalized with the microtubule network. Listeria more frequently invaded cells with mobilized calprotectin. Calprotectin mobilization was listeriolysin O-dependent and required calcium (extracellular and intracellular) and an intact microtubule network. In the presence of preformed microtubules in vitro, the anti-Listeria activity of calprotectin was abrogated. To facilitate intraepithelial survival, therefore, Listeria mobilizes calprotectin to colocalize with cytoplasmic microtubules, subverting anti-Listeria activity and autonomous cellular immunity.Mucosal Immunology (2009) 2, 43–53; doi:10.1038/mi.2008.63; published online 1 October 2008 [ABSTRACT FROM AUTHOR]

A time series of whole-genome transcription profiling of Escherichia coli K-12 W3110 was performed during a carbon-limited fed-batch process. The application of a constant feed rate led to the identification of a dynamic sequence of diverse carbon limitation responses (e.g., the hunger response) and at the same time provided a global view of how cellular and extracellular resources are used: the synthesis of high-affinity transporters guarantees maximal glucose influx, thereby preserving the phosphoenolpyruvate pool, and energy-dependent chemotaxis is reduced in order to provide a more economic "work mode." oS-mediated stress and starvation responses were both found to be of only minor relevance. Thus, the experimental setup provided access to the hunger response and enabled the differentiation of the hunger response from the general starvation response. Our previous topological model of the global regulation of the E. coli central carbon metabolism through the crp, cra, and relA/spoT modulons is supported by correlating transcript levels and metabolic fluxes and can now be extended. The substrate is extensively oxidized in the tricarboxylic acid (TCA) cycle to enhance energy generation. However, the general rate of oxidative decarboxylation within the pentose phosphate pathway and the TCA cycle is restricted to a minimum. Fine regulation of the carbon flux through these pathways supplies sufficient precursors for biosyntheses. The pools of at least three precursors are probably regulated through activation of the (phosphoenolpyruvate-)glyoxylate shunt. The present work shows that detailed understanding of the genetic regulation of bacterial metabolism provides useful insights for manipulating the carbon flux in technical production processes. [ABSTRACT FROM AUTHOR]

Certain strains of viridans streptococci bind platelets, which release ATP from dense granules and then aggregate. By hydrolyzing the released ATP to the platelet agonist, ADP, cell wall-associated ATPase activity of Streptococcus sanguis may amplify the aggregation of platelets. To identify and characterize this ecto-ATPase activity, whole cells were incubated with [14C]-ATP. The cell-free nucleotides were separated by thin-layer chromatography and quantified by liquid scintillation counting. Whole-cell activity showed temperature and pH optima in the physiological range. To isolate a soluble fraction with ATPase activity from the cell wall, whole cells were digested under osmotically stable conditions to produce protoplasts. Protoplasts and cells were separated from soluble cell wall materials by centrifugation. ATPase activity in cell fractions was identified by zymograms of native 8% polycrylamide gels after electrophoresis. The ecto-ATPase preparation, membrane and cytoplasmic ATPase in lysed protoplasts showed different zymograms and sensitivity to inhibition by DCCD, ouabain vanadate, azide and NEM. In electron micrographs of ultrathin sections of cells of S. sanguis, ATPase activity was localized to the cell wall. Since the pattern of localization to the wall changed with the phase of growth, the ecto-ATPase of S. sanguis may be associated with the development and maintenance of the cell wall. [ABSTRACT FROM AUTHOR]

Pretreatment of secondary effluents, containing relatively high concentrations of colloidal particles, suspended solids, dissolved organics and high level of biological activity, is required to reduce fouling of reverse osmosis (RO) membranes treating these effluents. Various indices are used to evaluate pretreatment efficacy. The effect of two different pretreatments for secondary effluent (BCMF - biofiltration, coagulation and microfiber filtration) vs. ultrafiltration (UF) were evaluated for their effect in reducing the fouling potential of the effluent as expressed by the indices of BOD (biofouling), TOC (organic and biofouling), and MFI 0.45 (colloidal fouling). Actual RO fouling tests were conducted using identical RO flow cells at constant flux conditions. Fouled membrane autopsies were subsequently carried out at the end of each test run. The actual fouling based on real-time performance and post-operation autopsies were then correlated to the fouling indices. The results showed that BCMF pretreatment significantly reduced the fouling potential as reflected in all three indices, but UF pretreatment process reduced BOD and MFI 0.45 to a significantly greater extent. RO membranes were in general fouled more severely by BCMF treated effluents as reflected in increased transmembrane pressure (TMP). This correlated with BOD and MFI 0.45 analyses of the treated effluents and with membrane autopsies at the end of the run. For both treatments, the calculated biofilm porosity dropped as the experiments were carried out for longer periods. As expected, the hydraulic resistance of the fouling layer was found to contribute significantly more to deterioration of RO performance than biofilm-enhanced osmotic pressure for both BCMF-RO and UF-RO. Image 1 • Biofilter followed by string microfilter (BCMF) not as effective a pretreatment as UF. • MFI and BOD correlated with actual fouling of RO by tertiary wastewater for BCMF. • TOC correlated with actual fouling of RO by tertiary wastewater for UF. • Dominant contribution to TMP rise was increased hydraulic resistance of biofilm. • Biofilm porosity dropped with fouling experiment duration. [ABSTRACT FROM AUTHOR]

An abstract of the article "Cascade-Like Modification of Immobilized Proteins Applying a Magnetically Controlled Fluidic System," by R. Brakowski and colleagues is presented.