Isolation and Characterization of Phenol-Degrading Soil Bacterium Xanthobacter flavus

A soil bacterium isolated from a contaminated site degraded phenol when provided as the sole carbon and energy source in the medium. The bacterium was identified as Xanthobacter flavus MTCC 9130. This microbial strain was able to tolerate phenol up to 1000 mg L^?1 concentration. The lag phase increased with the increase in phenol concentration. The optimum growth temperature was 37°C. The organism efficiently utilized phenol and could degrade it completely within 120 h when initial concentration was less than 600 mg L^?1. Degradation of phenol was through ortho pathway, enzyme assay through cell-free extract exhibited the presence of catechol 1,2-dioxygenase. The specific activity was 0.146 μ mol min^?1 mg^?1 protein. However, higher concentrations of phenol in the medium had a negative effect on the growth of the bacterium. Hence this ability of Xanthobacter flavus can be effectively used for bioremediation studies of phenol-contaminated sites.     

Rapid and sensitive sandwich enzyme-linked immunosorbent assay for detection of staphylococcal enterotoxin B in cheese.

A rapid and sensitive screening sandwich enzyme-linked immunosorbent assay (ELISA) was developed for the detection of staphylococcal enterotoxin B (SEB) in cheese by using a highly avid anti-SEB antibody (Ab) as the capture Ab (CAb) and as the biotinylated Ab conjugate. The glutaraldehyde fixation method for the immobilization of CAb on polystyrene dipsticks was superior to the adsorption fixation and the adsorption-glutaraldehyde fixation methods. The glutaraldehyde fixation method resulted in a higher surface-saturating CAb concentration as evaluated by the peroxidase saturation technique and by the ability of the CAb-coated dipstick to discriminate between positive and negative controls (index of discrimination). Of nine blocking agents used alone or in pairs, lysine-human serum albumin, bovine serum albumin, human serum albumin, and gelatin effectively saturated available sites on the CAb-coated dipsticks without causing interference with the antigen-Ab reactions. The addition of 1% polyethylene glycol to the diluent of the biotinylated anti-SEB Ab conjugate improved the detection of SEB. A concentration of 4% polyethylene glycol allowed a 5-min reaction time for the streptavidin-biotin-horseradish peroxidase conjugate. Cheddar cheese homogenate reduced the sensitivity of the SEB assay; however, the sensitivity was restored when 1.6% (wt/vol) of either a nonionic detergent (Mega-9) or two zwitterionic detergents (Zwittergent 3-10 and 3-12 detergent) was added to the diluent. By using the rapid sandwich ELISA, a minimum of 0.5 to 1.0 ng of SEB per ml was detected within 45 min. The whole procedure for the analysis of the cheddar cheese samples was completed within 1 h.(ABSTRACT TRUNCATED AT 250 WORDS)     

Rapid and sensitive sandwich enzyme-linked immunosorbent assay for detection of staphylococcal enterotoxin B in cheese

A rapid and sensitive screening sandwich enzyme-linked immunosorbent assay (ELISA) was developed for the detection of staphylococcal enterotoxin B (SEB) in cheese by using a highly avid anti-SEB antibody (Ab) as the capture Ab (CAb) and as the biotinylated Ab conjugate. The glutaraldehyde fixation method for the immobilization of CAb on polystyrene dipsticks was superior to the adsorption fixation and the adsorption-glutaraldehyde fixation methods. The glutaraldehyde fixation method resulted in a higher surface-saturating CAb concentration as evaluated by the peroxidase saturation technique and by the ability of the CAb-coated dipstick to discriminate between positive and negative controls (index of discrimination). Of nine blocking agents used alone or in pairs, lysine-human serum albumin, bovine serum albumin, human serum albumin, and gelatin effectively saturated available sites on the CAb-coated dipsticks without causing interference with the antigen-Ab reactions. The addition of 1% polyethylene glycol to the diluent of the biotinylated anti-SEB Ab conjugate improved the detection of SEB. A concentration of 4% polyethylene glycol allowed a 5-min reaction time for the streptavidin-biotin-horseradish peroxidase conjugate. Cheddar cheese homogenate reduced the sensitivity of the SEB assay; however, the sensitivity was restored when 1.6% (wt/vol) of either a nonionic detergent (Mega-9) or two zwitterionic detergents (Zwittergent 3-10 and 3-12 detergent) was added to the diluent. By using the rapid sandwich ELISA, a minimum of 0.5 to 1.0 ng of SEB per ml was detected within 45 min. The whole procedure for the analysis of the cheddar cheese samples was completed within 1 h.(ABSTRACT TRUNCATED AT 250 WORDS)     

Development of a chemically defined ram semen diluent (RSD-1)

A chemically defined ram semen diluent (RSD-1) has been developed. RSD-1 maintained spermatozoal motility of diluted semen containing approximately 800 million spermatozoa ml⁻¹ during cooling to 15°C and its storage for 1 h. Motility was further maintained when the cooled semen was diluted to 100 million spermatozoa ml⁻¹ and incubated at 38°C for about 24 h. In contrast, a conventional milk-based diluent supported motility for less than 6 h at 38°C. Spermatozoal motility was influenced by the buffering capacity, osmolarity and the presence or absence of macromolecules and calcium in the chemically defined diluent. Among the organic buffers tested, MOPS (3-(N-morpholino)propanesulphonic acid) had a marked influence on the maintenance of spermatozoal motility. The presence of MOPS also overcame the detrimental effects of 2 mM calcium in Krebs Ringer improved (KR-I) buffer.     

Molybdate reduction by Pseudomonas sp. strain DRY2

Aims: To isolate and characterize a potent molybdenum‐reducing bacterium. Methods and Results: A minimal salt medium supplemented with 10 mmol l^?1 molybdate, glucose (1·0%, w/v) as a carbon source and ammonium sulfate (0·3%, w/v) as a nitrogen source was used in the screening process. A molybdenum‐reducing bacterium was isolated and tentatively identified as Pseudomonas sp. strain DRY2 based on carbon utilization profiles using Biolog GN plates and partial 16S rDNA molecular phylogeny. Strain DRY2 produced 2·4, 3·2 and 6·2 times more molybdenum blue compared to Serratia marcescens strain DRY6, Enterobacter cloacae strain 48 and Eschericia coli K12, respectively. Molybdate reduction was optimum at 5 mmol l^?1 phosphate. The optimum molybdate concentration that supported molybdate reduction at 5 mmol l^?1 phosphate was between 15 and 25 mmol l^?1. Molybdate reduction was optimum at 40°C and at pH 6·0. Phosphate concentrations higher than 5 mmol l^?1 strongly inhibited molybdate reduction. Inhibitors of electron transport system such as antimycin A, rotenone, sodium azide and cyanide did not inhibit the molybdenum‐reducing enzyme activity. Chromium, copper, mercury and lead inhibited the molybdenum‐reducing activity. Conclusions: A novel molybdenum‐reducing bacterium with high molybdenum reduction capacity has been isolated. Significance and Impact of the Study: Molybdenum is an emerging global pollutant that is very toxic to ruminants. The characteristics of this bacterium suggest that it would be useful in the bioremediation of molybdenum pollutant.     

A biosurfactant from Burkholderia cenocepacia BSP3 and its enhancement of pesticide solubilization

Aims: To isolate a biosurfactant (BS)‐producing bacterium, to characterize the BS properties and to evaluate its ability to enhance pesticide solubilization for further application in environmental remediation. Methods and Results: Five BS‐producing bacteria were isolated from fuel oil‐contaminated soil. Among them, Burkholderia cenocepacia BSP3 exhibited the highest emulsification index and was chosen for further study. Glucose‐containing medium supplemented with nitrate or sunflower seed oil provided suitable conditions for growth and BS production. The BS was identified as a glucolipid, having a critical micelle concentration (CMC) of 316 mg l^?1. It could lower the surface tension of deionized water to 25 ± 0·2 mN m^?1 and exhibited good emulsion stability. Finally, the application of the BS to facilitate pesticide solubilization demonstrated that this BS at the concentration below and above its CMC could enhance the apparent water solubility of three pesticides, i.e. methyl parathion, ethyl parathion and trifluralin. Conclusions: Burkholderia cenocepacia BSP3 is a BS‐producing bacterium isolated from oil‐contaminated soil. The BS was identified as a glucolipid having a molecular mass of 550·4 g mol^?1. An apparent yield of the BS was 6·5 ± 0·7 g l^?1. This glucolipid‐type BS noticeably enhanced pesticide solubilization suggesting its role in environmental remediation. Significance and Impact of the Study: A glucolipid type BS normally found in marine micro‐organisms was isolated from a soil‐bacterium. Due to its surface active properties and good performance in enhancement of pesticide solubilization, it could be used as a solubilizing agent for environmental remediation and synergistic treatment with bioremediation of pesticide‐contaminated soil.     

Covalent binding sites of victorin in oat leaf tissues detected by anti-victorin polyclonal antibodies

Polyclonal antibodies against victorin, the host-specific toxin produced by Cochliobolus victoriae, were raised in rabbits immunized with a victorin-bovine serum albumin conjugate. The antibodies were purified from serum by protein A column chromatography and characterized by indirect and direct enzymelinked immunosorbent assays (ELISA). The concentration of victorin that inhibited anti-victorin antibody binding by 50% was 10 nanograms per milliliter in an indirect ELISA. The lowest concentration of victorin detectable was 10 picograms per milliliter. In a direct ELISA, 25 nanograms per milliliter of victorin inhibited binding of victorin-horseradish peroxidase conjugate by 50%. In vivo and in vitro covalent binding of victorin to proteins in susceptible and resistant oat (Avena sativa) tissue was examined by western blotting assays using anti-victorin antibody and a second antibody conjugated with ¹²⁵I or alkaline phosphatase. In vivo binding of victorin to proteins of 100 and 45 kilodaltons was observed in both susceptible and resistant cultivars of oats. Victorin also bound in vitro to proteins of 100, 65, and 45 kilodaltons in both susceptible and resistant oats. The data indicate that victorin binds covalently to the same sites in susceptible and resistant genotypes of oats.     

Analysis of rates of receptor-mediated endocytosis and exocytosis of a fluorescent hapten-protein conjugate in murine macrophage: Implications for antigen processing

A novel fluorescent hapten-protein conjugate was constructed to monitor the events required for CD 4⁺ T lymphocyte recognition of antigenic proteins. Previous studies utilizing the probe demonstrated that the hapten-protein was localized to an acidic endocytic compartment within the macrophage and that the hapten-protein was sensitive to multiple intracellular events including enzymatic degradation, acidification, and disulfide bond reduction. More importantly, recent experiments indicated that efficient internalization of the probe was dependent upon specific recognition of the hapten. Therefore, the present report addressed the effect of receptor-mediated endocytosis upon the processing of the hapten-protein within murine peritoneal macrophage. These studies determined that the rate of endocytosis was significantly faster than the rate of exocytosis. Specifically, the rate of exocytosis was estimated to be 3.4 × 10⁴ s^?1 based on a unimolecular rate constant. Although at higher concentrations, a slightly slower rate was observed (1.9 × 10⁴ s^?1). This study also represented one of the first efforts to measure the intracellular concentration effect typically associated with receptor-mediated endocytosis. Experiments involving a radioactively labeled hapten-protein conjugate revealed that the probe was at 100-fold higher concentration within the endocytic vesicles when compared to the extracellular media. The intracellular mechanism involved in this phenomenon was discussed as well as the implications of these findings upon MHC II-peptide binding.     

Comparison of the sensitivity of the serological latex and ELISA tests

A sensitivity of the serological latex and ELISA tests were compared in carnation mottle virus diagnosis. For the latex test carnation mottle virus (CaMV) antiserum was sensibilized with latex suspension for RF-test. Sensibilized antiserum was used in 1: 200 dilution, as compared with fresh antiserum. For ELISA the γ-globuline fraction of antiserum was conjugated with alkaline phosphatase. The optimal dilution in both, CaMV fraction of antisera for coating of plates and γ-globuline-enzyme conjugate were in the ratio of 1: 500, 2 μg of antibodies in 1 ml. The dilution end point of carnation mottle virus in sap from carnation leaves was 1.6 × 10^?4 to 1.25 × l0^?5 and 1 × 10^?4 to 1.25 × l0^?5, when serological latex and ELISA tests were used. As indicated, ELISA as compared to the latex test was found to be more sensitive for carnation mottle diagnosis. As the latex test is considered to be simpler and cheaper, and in addition, showing the same assurance as the biological test onChenopodium amaranticolor, the latex test is recommended for carnation mottle virus detection.     

Electrophoretic Heterogeneity Limits the Utility of Streptavidin-β-Galactosidase as a Probe in Free Zone Capillary Electrophoresis Separations

Single molecule assays were performed on streptavidin-β-galactosidase using a capillary electrophoresis-based protocol in order to assess the suitability of single molecule β-galactosidase assays for adaptation to the detection of single copies of target DNA. The conjugate was found to have a heterogeneous catalytic rate, showing an average rate of 44,000 ± 24,000 min^?1, which is similar to that of the unmodified enzyme. Electrophoretic mobility was also measured on individual molecules and determined to be ?1.32 × 10^?4 ± 0.19 × 10^?4 cm²V^?1s^?1. The variance in mobility was several times that reported for the unmodified enzyme. The electrophoretic heterogeneity was found to result in the formation of a broad window of peaks in the resultant electropherograms of free zone separations of small plugs of streptavidin-β-galactosidase. This range of mobilities largely overlapped with that of the conjugate bound to primer and plasmid containing a target DNA sequence. This overlap suggests that the separation of free conjugate from that bound to target DNA, which is a requirement for application of the single enzyme molecule assay to the detection of target DNA sequences, is not plausible using free zone capillary electrophoresis.     

A (1→3,1→4)-β-glucan-specific monoclonal antibody and its use in the quantitation and immunocytochemical location of (1→3,1→4)-β-glucans

Monoclonal antibodies were raised against a (1→3,1→4)-β-glucan-bovine serum albumin (BSA) conjugate. One antibody (BG1) selected for further characterization, was specific for (1→3,1→4)-β-glucan, displaying no binding activity against a (1→3)-β-glucan-BSA conjugate and minimal binding against a cellopentaose-BSA conjugate. A range of oligosaccharides was prepared by enzymatic digestion of (1→3,1→4)-β-glucan, purified by size exclusion chromatography and characterized by ¹H-NMR and anion exchange chromatography. These (1→3,1→4)-β-oligoglucosides, together with (1→3)-β- and (1→4)-β-oligoglucosides were used to characterize the binding site of the monoclonal antibody (BG1) by competitive inhibition. The monoclonal antibody showed maximal binding to a heptasaccharide with the structure Glc(1→3) Glc(1→4) Glc(1→4) Glc(1→3) Glc(1→4) Glc(1→4) Glc and was determined to have an affinity constant of 3.8 × 10⁴ M⁻¹ for this oligoglucoside. The monoclonal antibody (BG1) has been used to develop a sensitive sandwich ELISA for the specific quantitation of (1→3,1→4)-β-glucans. The assay operates in the range 1–10 ng ml⁻¹ and shows no significant cross-reaction with tamarind xyloglucan, wheat endosperm arabinoxylan or carboxymethyl-pachyman ((1→3)-β-glucan). When used with a second-stage, rabbit anti-mouse gold conjugate and viewed under the electron microscope, the monoclonal antibody probe was found to bind strongly to the walls of the aleurone in thin sections of immature wheat (Triticum aestivum) cv. Millewa grains but not to the middle lamella region. A previously described specific anti-(1→3)-β-glucan antibody (Meikle et al., 1991) bound to discrete patches on the aleurone walls, believed to be plasmodesmata.     

Production and Properties of Lipase from a Newly Isolated Chromobacterium

Out of some 750 strains of microorganisms, a potent bacterium for lipase production was isolated from soil and was identified as Chromobacterium viscosum.

The bacterium accumulates lipase in culture fluid when grown aerobically at 26°C for 3 days in a medium composed of soluble starch, soy bean meal, lard and inorganic salts.

Chromobacterium lipase had an optimum pH of 7.0 for activity at 37°C, and an optimal temperature of 65°C at pH 7.0. The enzyme retained 80% of the activity when heated for 10 min at 70°C. This lipase was capable of hydrolyzing a variety of natural fats and oils, and it was more active on lard and butter than on olive oil. The activity was stimulated by Ca²⁺, Mg²⁺, Mn²⁺ and inhibited by Cu²⁺, Hg²⁺ and Sn²⁺. It was not diminished but rather stimulated by a high concentration of bile-salts.     

Development of monoclonal antibody against isoquinoline alkaloid coptisine and its application for the screening of medicinal plants

In the development of immunoassay technique, the design of hapten containing a functional group suitable for protein conjugate is the key step for the preparation of antibodies against small molecules. Coptisine (MW 320), a bioactive constituent of Berberis and Coptis species, is small as an immunogen. In addition, coptisine has no reactive group in molecule for conjugating with a protein. To overcome this problem, 9-O-carboxymethyl-berberrubine was designed and conjugated with carrier protein. In order to confirm its immunogenicity, the ratio of hapten in the conjugate was determined by matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS). After immunization, hybridomas secreting antibodies against coptisine were produced by fusing splenocytes with mouse myeloma cell line, P3-X63-Ag8-653. Among hybridomas, the clone 2A1 secreting anti-coptisine monoclonal antibody (MAb) 2A1-9E-1 was obtained through the limited dilution method. The MAb-based enzyme-linked immunosorbent assay (ELISA) against coptisine was developed and characterized. The linear range of the assay in this ELISA method was extended from 1.56 to 25 μg ml⁻¹ possessing the detection limit of 1.56 μg ml⁻¹. The established ELISA using MAb 2A1-9E-1 was applied for the survey of isoquinoline alkaloids in various medicinal plants.     

Antifungal action of chitosan in combination with fungicides in vitro and chitosan conjugate with gallic acid on tomatoes against Botrytis cinerea

In the present work, a positive effect was obtained by using low molecular weight chitosan compounds in combination with synthetic fungicides. Antifungal activity against Botrytis cinerea, determined by the radial growth method, was more than 75%, with a 25?×?10^??10 g/L concentration of fludioxonil or difenoconazole in compounds. Metabolic activity of B. cinerea fungus was about 15% when using a chitosan compound containing fludioxonil at a concentration of 25?×?10^??7 g/L. The combined action of chitosan with difenoconazole at a fungicide concentration of 25?×?10^??4 g/L is 2–3 times more effective than the action of each component separately. Results of studies for artificially inoculated B. cinerea tomato fruit when treated with low molecular chitosan and chitosan conjugate with gallic acid reduced the frequency of rotting fruit by 50 and 83%, respectively. Chitosan-gallic acid conjugate were obtained from chitosans with Mw of 28 kDa (Ch28GA) was proved to be effective as a preventive treatment for 3 days and can potentially be used as a biofungicide against B. cinerea on tomatoes in the post-harvest period.

     

The toxicity of tributyltin oxide to the wood-boring beetles Lyctus brunneus Steph. and Anobium punctatum (Deg.)

When tributyltin oxide (TBTO) was tested by British Standard 3653 against Lyctus brunneus, 0·5 % solution, equivalent to 0·72 g/m₂ surface application, gave almost complete protection. Tests to BS 3651, using larvae of Anobium punctatum transferred into fully impregnated wood gave toxic limits of 1·39–2·93 kg/m³ TBTO when benzene was used as diluent. The use of white spirit as diluent gave lower toxic limits, probably due to combined toxic action of TBTO and white spirit residues. TBTO appears to have no contact action against the insects tested. Probit analysis of the test with A. punctatum gave an LD 50 of 0·254 kg/m³ and an LD99 of 3 kg/m³. The advantage of treating results by probit analysis rather than by deriving ‘toxic limits’ is discussed.     

Arming α2-macroglobulin with ricin A chain forms a cytotoxic conjugate that inhibits protein synthesis and kills human fibroblasts

A conjugate containing α₂-macroglobulin and highly purified ricin A chain was made using N-succinimidyl-3-(2-pyridyldithio)propionate. Radioimmunoassay indicated that it contained 1.2 mol A chain per mol α₂-macroglobulin. The conjugate inhibited polyuridylic-acid directed translation by rat liver ribosomes and protein synthesis in human fibroblasts. There was a 90 min lag period before the beginning of inhibition in fibroblasts, but complete inhibition could be achieved. By measuring protein synthesis as a function of protein concentration, it was demonstrated that 8.25·10^?9M conjugate was required to inhibit 50% of protein synthesis in 6 h. To achieve the same level of inhibition, 165-times more (1.3·10^?6M) unconjugated A chain was required, and 180-times less ricin (4.6·10^?11M). Ricin was more than 28 000 times more inhibitory than A chain alone. The presence of α₂-macroglobulin did not increase the cytotoxicity of unconjugated A chain, and it even protected the cells to a slight extent. The inhibitory action of the conjugate was blocked by antibodies specific for α₂-macroglobulin or ricin, and it was not prevented by galactose or antibodies specific for ricin B chain. Electron microscopy of the conjugate indirectly labelled with ferritin demonstrated that it was internalized by receptor mediated endocytosis through coated pits. These data indicate that the A chain portion of the conjugate survives the conditions in the lysosomes to the extent that it retains its ability to inactivate cytoplasmic ribosomes.     

Enzyme‐linked immunosorbent assay by enhanced chemiluminescence detection for the standardization of estrogenic miroestrol in Pueraria candollei Graham ex Benth

Miroestrol (ME) is a potent phytoestrogen from the P. candollei tuberous root. It has been approved for use in clinical trials due to its beneficial effect on disorders associated with estrogen deficiency. To ensure medical efficacy and safety, high performance analytical methods for ME analysis are required to standardize products from the P. candollei root. An enhanced chemiluminescence enzyme‐linked immunosorbent assay (ECL‐ELISA) was developed and validated using a polyclonal antibody against ME and a chemiluminescent system of luminol–H₂O₂–horseradish peroxidase‐4‐(1‐imidazolyl) phenol. The ECL‐ELISA system exhibited linearity over a concentration range of 0.31–10.00 ng mL^?1, for which the relative standard variation (%RSD) was less than 10% for both intra‐ and interplate determinations. The ECL‐ELISA is reliable for the determination of ME as reflected by the high recovery percentage (101.22–103.06%). As a comparative analysis, the ME content in each sample determined by ECL‐ELISA was correlated with high coefficients of determination with colorimetric ELISA (R² = 0.998) and high performance liquid chromatography (HPLC) (R² = 0.998) methods. The ECL‐ELISA method could be applied to all of the commercial products containing P. candollei root, when the products contain between 0.706 ± 0.046 and 13.123 ± 0.794 µg g^?1 dry wt. of ME. This method is useful as a high performance analytical method for the quantity control of ME in raw materials and end products at both the research and industrial levels. Copyright © 2014 John Wiley & Sons, Ltd.     

A surface plasmon resonance assay for characterisation and epitope mapping of anti‐GLP‐1 antibodies

The incretin hormone glucagon‐like peptide‐1 (GLP‐1) has been subject to substantial pharmaceutical research regarding the treatment of type 2 diabetes mellitus. However, quantification of GLP‐1 levels remains complicated due to the low circulation concentration and concurrent existence of numerous metabolites, homologous peptides, and potentially introduced GLP‐1 receptor agonists. Surface plasmon resonance (SPR) facilitates real‐time monitoring allowing a more detailed characterisation of the interaction compared with conventional enzyme‐linked immunosorbent assays (ELISA). In this paper, we describe the development of the first SPR assays for characterisation of anti‐GLP‐1 antibodies for ELISA purposes. Binding responses were obtained on covalently immobilised anti‐GLP‐1 antibodies at 12°C, 25°C, and 40°C and fitted to a biomolecular (1:1) interaction model showing association rates of 1.01 × 10³ to 4.54 × 10³ M^?1 s^?1 and dissociation rates of 3.56 × 10^?5 to 1.56 × 10^?3 s^?1 leading to affinities of 35.2 to 344 nM, depending on the temperature. Determination of thermodynamic properties revealed an enthalpy driven interaction (ΔH < ΔS < 0) with higher affinities at lower temperatures due to the formation and stabilisation of hydrogen bonds within the binding site primarily composed of polar amino acids (ΔC_p < 0). Pair‐wise epitope mapping was performed on captured anti‐GLP‐1 antibodies followed by subsequent interaction with GLP‐1 (7‐36) and other anti‐GLP‐1 antibodies. A global evaluation of every binding response led to an epitope map elucidating the potential of various anti‐GLP‐1 antibody pairs for sandwich ELISA and hence pinpointing the optimal antibody combinations. The SPR assays proved capable of providing vital information for ELISA development endorsing it as a useful optimisation tool.     

V max per bacterium and turnover rate per bacterium for glucose mineralization in natural waters

Specific activity of aquatic bacteria, which indicates average heterotrophic activity per bacterial cell, was determined asV _max per bacterium and turnover rate per bacterium for glucose mineralization at different sites (river and estuary) in north Humberside, northeast England.V _max per bacterium ranged from 0.05×10⁻¹³ to 52.2×10⁻¹³ mg/h and turnover rate per bacterium from 0.05×10⁻⁸ to 88.3×10⁻⁸ ml/h. Highest mean values were found at river sites and the lowest at an outer estuary site, although there was considerable variation at each site and ranges from all sites overlapped. Also, ranges ofV _max per bacterium from Humberside sites in general overlapped published ranges for sites in other geographical areas.V _max per bacterium and turnover rate per bacterium were significantly correlated with some environmental variables, which suggests that they are of ecological significance.     

A Label-Free Nanogold DNAzyme-Cleaved Surface-Enhanced Resonance Raman Scattering Method for Trace UO2 2+ Using Rhodamine 6G as Probe

In pH?5.5 2-(N-morpholino)-ethanosulfonic acid buffer solution containing 0.25 M NaCl at 80 °C, the single-stranded substrate DNA hybridizes with the enzyme DNA to form double-stranded DNA (dsDNA). The substrate chain of dsDNA could be cracked catalytically by UO₂ ²⁺ to produce a short single-stranded DNA (ssDNA) that adsorbed on the nanogold (NG) surface to form a stable nanogold–ssDNA conjugate and then further combine with rhodamine 6G (RhG) to form a NG–ssDNA–RhG conjugate that can be monitored by the surface-enhanced resonance Raman scattering (SERRS) spectral technique at 1,360 cm^?1. Under the selected conditions, the increased SERRS intensity ΔI ₁₃₆₀ was linear to UO₂ ²⁺ concentration in the range of 5–125 nmol/L, with a detection limit of 1.6 nmol/L. Using a 0.5-μmol/L Hg²⁺ as enhancer, a 2.5–100-nmol/L UO₂ ²⁺ can be determined.