Anaerobic-aerobic sequencing bioreactors improve energy efficiency for treatment of personal care product industry wastes

Personal care product (PCP) industry liquid wastes contain shampoo residues, which are usually treated by aerobic activated sludge (AS). Unfortunately, AS is expensive for PCP wastes because of high aeration and energy demands, whereas potentially energy-positive anaerobic designs cannot meet effluent targets. Therefore, combined anaerobic-aerobic systems may be the best solution. Seven treatment systems were assessed in terms of energy and treatment performance for shampoo wastes, including one aerobic, three anaerobic (HUASB, AHR and AnCSTR) and three anaerobic-aerobic reactor designs. COD removals were highest in the HUASB-aerobic (87.9 ± 0.4%) and AHR-aerobic (86.8±0.5%) systems, which used 69.2% and 62.5% less energy than aerobic AS. However, actual methane production rates were low relative to theoretical in the UASB and AHR units (∼10% methane/COD removed) compared with the AnCSTR unit (∼70%). Anaerobic-aerobic sequence reactors show promise for treating shampoo wastes, but optimal designs depend upon whether methane production or COD removal is most important to operations.

Nitrification in hybrid bioreactors treating simulated domestic wastewater

AIM

To provide deeper insights into nitrification process within aerobic bioreactors containing supplemental physical support media (hybrid bioreactors).

METHODS AND RESULTS

Three bench-scale hybrid bioreactors with different media size and one control bioreactor were operated to assess how biofilm integrity influences microbial community conditions and bioreactor performance. The systems were operated initially at a 5-day hydraulic retention time (HRT), and all reactors displayed efficient nitrification and chemical oxygen demand (COD) removal (>95%). However, when HRT was reduced to 2.5 days, COD removal rates remained high, but nitrification efficiencies declined in all reactors after 19 days. To explain reduced performance, nitrifying bacterial communities (ammonia-oxidizing bacteria, AOB; nitrite-oxidizing bacteria, NOB) were examined in the liquid phase and also on the beads using qPCR, FISH and DGGE. Overall, the presence of the beads in a reactor promoted bacterial abundances and diversity, but as bead size was increased, biofilms with active coupled AOB-NOB activity were less apparent, resulting in incomplete nitrification.

CONCLUSIONS

Hybrid bioreactors have potential to sustain effective nitrification at low HRTs, but support media size and configuration type must be optimized to ensure coupled AOB and NOB activity in nitrification.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study shows that AOB and NOB coupling must be accomplished to minimize nitrification failure.

Low-energy treatment of colourant wastes using sponge biofilters for the personal care product industry

Four trickling biofilter designs were assessed as low-energy alternatives to aerobic activated sludge (AS) for the treatment of personal care product industry wastes. The designs included partially submerged packed-media and sponge reactors with and without active aeration. Partial submergence was used to reduce active aeration needs. Simulated colourant wastes (up to COD=12,480 mg/L, TN=128 mg/L) were treated for 201 days, including wastes with elevated oxidant levels. COD and TN removal efficiencies were always >79% and >30% (even without aeration). However, aerated sponge reactors consistently had the highest removal efficiencies, especially for TN (∼60%), and were most tolerant of elevated oxidants. This study shows sponge biofilters have great potential for treating colourant wastes because they achieve high treatment efficiencies and reduce energy use by >40% relative to AS systems.

Mercury levels in sediments and mangrove oysters, Crassostrea rizophorae, from the north coast of Villa Clara, Cuba

Total mercury levels were quantified in sediments and oyster tissues (Crassostrea rizophorae) from the Sagua la Grande River estuary and offshore mangrove keys 19 km downstream of a chlor-alkali plant (CAP) in Villa Clara, Cuba. Relatively elevated total mercury levels were found in sediments from the estuary itself, ranging from 0.507 to 1.81 μg g(-1) dry weight. However, levels were lower in sediments from the keys farther from the estuary. Oyster mercury levels were always acceptable for human consumption, although levels significantly correlated in sediments and oysters across sampling sites (p < 0.05), which suggests that mercury from the CAP is impacting coastal water quality conditions.

Feasibility tests for treating shampoo and hair colorant wastewaters using anaerobic processes

Wastes from the personal care product (PCP) industry are often high in biodegradable carbon, which makes them amenable to aerobic biological treatment, although process costs are usually high due to aeration inefficiencies, high electricity demand and production of large amounts of sludge. As such, anaerobic treatment technologies are being considered to lower net energy costs by reducing air use and increasing methane production. To assess the amenability of PCP wastes to anaerobic treatment, methane yields and rates were quantified in different anaerobic reactors treating typical PCP wastes, including wastes from shampoo and hair colorant products. Overall, shampoo wastes were more amenable to methanogenesis with almost double the methane yields compared with colour wastes. To assess relevant microbial guilds, qPCR was performed on reactor biomass samples. Methanosaetaceae abundances were always significantly higher than Methanosarcinaceae and Methanomicrobiales abundances (P < 0.05), and did not differ significantly between waste types. Although colour wastes were less amenable to anaerobic treatment than shampoo wastes, differences cannot be explained by relative microbial abundances and probably result from the presence of inhibiting compounds in hair colorants (e.g., oxidants) at higher levels. Results showed that anaerobic technologies have great potential for treating PCP wastes, but additional work is needed to establish the basis of elevated methane yields and inhibition, especially when colorant wastes are present.

Assessment of total mercury levels in Clarias gariepinus from the Sagua la Grande River, Cuba

Total mercury levels (Thg) were quantified in Clarias gariepinus captured from the Sagua la Grande River (Cuba) in the vicinity of an active chlor-alkali plant, and relationships among place of capture; fish size, weight, and sex; and THg levels were assessed. THg levels ranged from 67 to 375 ng/g ww in collected fish, never exceeding the Cuban recommended maximum limit for fish consumption of 500 ng/g ww. No significant correlation was observed between mercury levels and fish allometric characteristics (p < 0.05); however, levels were significantly higher in fish captured below the chlor-alkali facility, suggesting a connection between mercury bioaccumulation and plant discharges.

A comparative assessment of molecular biological and direct microscopic techniques for assessing aquatic systems

Molecular techniques have clear value for community characterization; however, almost all previous datasets are based upon non-molecular measurements and it is hard to compare "old" data with "new" data because few correlations have been made. Therefore, the purpose of this evaluation was to simultaneously use molecular and non-molecular methods within the same sampling program to determine how data compare. Three methods were used for characterizing microbial populations in Lake 260 (L260) at Experimental Lakes Area (Ontario, Canada) during a whole-lake exposure study. Methods included whole-cell microscopic counts (for bacteria, cyanobacteria, algae and zooplankton), chlorophyll a, and small sub-unit (ssu)-rRNA hybridization using EUB-338, EUB-785, CYAN-785-a/b, EUCA-1379 and UNIV-1390 gene probes. Strong correlations were found between the EUB-785 probe signal and "bacteria minus cyanobacteria" direct counts, and the EUB-338 probe signal and "bacteria plus cyanobacteria" counts. Furthermore, the difference in probe signal between EUB-338 and EUB-785 (a presumptive signature for cyanobacteria and plastids) correlated with cyanobacterial direct counts and also with chlorophyll a. However, EUCA-1379 probe signal did not correlate with algae counts, and UNIV-1390 probe signal only correlated with total bacteria counts. Results suggest that, although ssu-rRNA methods are fast, reproducible, and specifically detect "viable" organisms, their use may be limited to non-eukaryotic populations unless new probes are developed that are more specific.

Bis-aryl triazoles as selective inhibitors of 11beta-hydroxysteroid dehydrogenase type 1

3-Aryl-5-phenyl-(1,2,4)-triazoles were identified as selective inhibitors of 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1). They are active in both in vitro and an in vivo mouse pharmacodynamic (PD) model. The synthesis and structure activity relationships are presented.

Water hyacinths (Eichhornia crassipes) as indicators of heavy metal impact of a large landfill on the Almendares River near Havana, Cuba

The Almendares River is central to recreational and other activities in Havana, Cuba. However, monitoring indicated significant heavy metal contamination in river sediments, especially below Calle 100, the largest landfill in Havana. This work extended previous sediment studies by determining complementary Cu, Pb, Ni, Cr, Cd, and Zn levels in indigenous water hyacinths (Eichhornia crassipes; EC) above and below the landfill. Pb, Cu, and Zn were significantly elevated in EC roots below the landfill and also correlated with sediment data (p < 0.05), implying elevated levels likely result from landfill activity and might be useful biomonitors as river remediation proceeds.

Field assessment of oxytetracycline exposure to the freshwater macrophytes Egeria densa Planch. and Ceratophyllum demersum L

In a microcosm study, two aquatic macrophytes, Egeria densa and Ceratophyllum demersum were exposed to nominal concentrations of 0, 5, 20, 50, and 250 microg/L oxytetracycline (n=3), plus 20 microg/L oxytetracycline amended with additional nitrogen (N) and phosphorus (P). Responses were monitored bi-weekly over a six-week exposure period. Both plant species exhibited a significant decline in growth in the 250 microg/L oxytetracycline and the N- and P-amended units. Decreased light penetration resulting from accumulating oxytetracycline by-products appears to be the primary modifier in the growth of these plants. Increased susceptibility to oxytetracycline exposure was noted in some paired plantings (e.g., E. densa root development), relative to individual plants in these treatments, however, no clear explanation for this response is available. Based on the toxicity data generated in this study, we estimate that current concentrations of oxytetracycline in freshwater environments do not pose a direct risk to E. densa and C. demersum.

Cryptic striations in the upper mantle revealed by hafnium isotopes in southeast Indian ridge basalts

The Earth's mantle is isotopically heterogeneous on length scales ranging from centimetres to more than 10(4) kilometres. This heterogeneity originates from partial melt extraction and plate tectonic recycling, whereas stirring during mantle convection tends to reduce it. Here we show that mid-ocean ridge basalts from 2,000 km along the southeast Indian ridge (SEIR) display a bimodal hafnium isotopic distribution. This bimodality reveals the presence of ancient compositional striations (streaks) in the Indian Ocean upper mantle. The number density of the streaks is described by a Poisson distribution, with an average thickness of approximately 40 km. Such a distribution is anticipated for a well-stirred upper mantle, in which heterogeneity is continually introduced by plate tectonic recycling, and redistributed by viscous stretching and convective refolding.

Fate and effects of enrofloxacin in aquatic systems under different light conditions

The fate and effects of fluoroquinolone antibacterials (FQ) in the environment is of significance because of apparent increased FQ resistance in environmental and clinical organisms. Here we simultaneously assessed the fate and effects of enrofloxacin (enro), an FQ often used in agriculture, on the chemistry and in situ microbial communities in receiving waters. We added enro to 25 microg/L in nine outdoor mesocosms maintained under three light conditions (in triplicate): full sunlight typical of the upper epilimnion (100% full-light exposure, FLE), partial shading typical of the lower epilimnion (28% FLE), and near-complete shading typical of the hypolimnion (0.5% FLE). Enro disappearance and ciprofloxacin (cipro) formation were monitored over time using LC/MS, and water chemistry and ambient microbial communities (using denaturing gradient gel electrophoresis; DGGE) were characterized. Enro half-lives were 0.8, 3.7, and 72 days for the 100%, 28%, and 0.5% FLE treatments, respectively, creating three distinct FQ exposure scenarios. Although FQ exposures ranged from approximately 6 microg/L for 24 h to approximately 21 microg/L for 30 days, no statistically significant exposure effects were noted in water quality or microbial communities (as indicated by whole-community 16S rDNA DGGE analysis and specific amplification of the QRDR region of gyrase A). Small changes in water chemistry were noted over time; however, changes could not be specifically attributed to FQs. In general, enro addition had minimal effect on water column conditions at the levels and durations used here; however, further investigation is needed to assess effects in aquatic sediments.

Novel ketal ligands for the glucocorticoid receptor: in vitro and in vivo activity

A novel series of selective ligands for the human glucocorticoid receptor is described. Structure-activity studies focused on variation of B-ring size, ketal ring size, and ketal substitution. These analogs were found to be potent and selective ligands for GR and have partial agonist profiles in functional assays for transactivation (TAT, GS) and transrepression (IL-6). Of these compounds, 27, 28, and 35 were evaluated further in a mouse LPS-induced TNF-alpha secretion model. Compound 28 had an ED(50) of 14.1 mg/kg compared with 0.5 mg/kg for prednisolone in the same assay.

Adamantyl triazoles as selective inhibitors of 11β-hydroxysteroid dehydrogenase type 1

Adamantyl triazoles were identified as selective inhibitors of 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1). They are active both in in vitro and in in vivo pharmacodynamic models. The synthesis and structure-activity relationships of these inhibitors are presented.

Novel N-Arylpyrazolo[3,2-c]-Based Ligands for the Glucocorticoid Receptor: Receptor Binding and in Vivo Activity

A novel series of selective ligands for the human glucocorticoid receptor (hGR) are described. Preliminary structure-activity relationships were focused on substitution at C-1 and indicated a preference for 3-, 4-, and 5-substituted aromatic and benzylic groups. The resulting analogues, e.g., 18 and 34, exhibited excellent affinity for hGR (IC(50) 1.9 nM and 2.8 nM, respectively) and an interesting partial agonist profile in functional assays of transactivation (tyrosine aminotransferase, TAT, and glutamine synthetase, GS) and transrepression (IL-6). The most potent compounds described in this study were the tertiary alcohol derivatives 21 and 25. These candidates showed highly efficacious IL-6 inhibition versus dexamethasone. The thiophenyl analogue 25 was evaluated in vivo in the mouse LPS challenge model and showed an ED(50) = 4.0 mg/kg, compared to 0.5 mg/kg for prednisolone in the same assay.

Magmatic and amagmatic seafloor generation at the ultraslow-spreading Gakkel ridge, Arctic Ocean

A high-resolution mapping and sampling study of the Gakkel ridge was accomplished during an international ice-breaker expedition to the high Arctic and North Pole in summer 2001. For this slowest-spreading endmember of the global mid-ocean-ridge system, predictions were that magmatism should progressively diminish as the spreading rate decreases along the ridge, and that hydrothermal activity should be rare. Instead, it was found that magmatic variations are irregular, and that hydrothermal activity is abundant. A 300-kilometre-long central amagmatic zone, where mantle peridotites are emplaced directly in the ridge axis, lies between abundant, continuous volcanism in the west, and large, widely spaced volcanic centres in the east. These observations demonstrate that the extent of mantle melting is not a simple function of spreading rate: mantle temperatures at depth or mantle chemistry (or both) must vary significantly along-axis. Highly punctuated volcanism in the absence of ridge offsets suggests that first-order ridge segmentation is controlled by mantle processes of melting and melt segregation. The strong focusing of magmatic activity coupled with faulting may account for the unexpectedly high levels of hydrothermal activity observed.

Discovery of abundant hydrothermal venting on the ultraslow-spreading Gakkel ridge in the Arctic Ocean

Submarine hydrothermal venting along mid-ocean ridges is an important contributor to ridge thermal structure, and the global distribution of such vents has implications for heat and mass fluxes from the Earth's crust and mantle and for the biogeography of vent-endemic organisms. Previous studies have predicted that the incidence of hydrothermal venting would be extremely low on ultraslow-spreading ridges (ridges with full spreading rates <2 cm x yr(-1)-which make up 25 per cent of the global ridge length), and that such vent systems would be hosted in ultramafic in addition to volcanic rocks. Here we present evidence for active hydrothermal venting on the Gakkel ridge, which is the slowest spreading (0.6-1.3 cm x yr(-1)) and least explored mid-ocean ridge. On the basis of water column profiles of light scattering, temperature and manganese concentration along 1,100 km of the rift valley, we identify hydrothermal plumes dispersing from at least nine to twelve discrete vent sites. Our discovery of such abundant venting, and its apparent localization near volcanic centres, requires a reassessment of the geologic conditions that control hydrothermal circulation on ultraslow-spreading ridges.

Design and synthesis of novel antibacterial agents with inhibitory activity against DNA polymerase III

4-Substituted 2-amino-6-(anilino)pyrimidines have been found to be selective inhibitors of DNA polymerase III, a replicative enzyme known to be essential in the DNA synthesis of Gram-positive bacteria. Among the analogues, 18 displayed an IC(50) of 10 microM against DNA polymerase III from Staphylococcus aureus.

Effect of oxygen level on simultaneous nitrogenase and sMMO expression and activity in Methylosinus trichosporium OB3b and its sMMO(C) mutant, PP319: aerotolerant N2 fixation in PP319

Soluble methane monooxygenase (sMMO) expression and activity were monitored under conditions that either promoted or suppressed the expression of nitrogenase in Methylosinus trichosporium OB3b wild-type (WT) and in its sMMO-constitutive mutant, PP319. Both WT and mutant cultures had reduced sMMO activity and protein levels under elevated O2 conditions (188 microM) compared with low O2 conditions (24 microM). Simultaneous N2 fixation also reduced sMMO activity in both cultures when O2 was low. However, when O2 levels were increased, nitrogenase expression ceased and sMMO activity was reduced by approximately 77% in the WT, whereas sMMO and nitrogenase expression and activity in PP319 were relatively unaffected by the higher O2 levels. Western immunoblot analysis showed that the nitrogenase Fe protein resolved as two components (apparent molecular mass of 30.5 and 32 kDa) in both the WT and PP319 when O2 levels were low. When O2 levels were high, only the 32-kDa form of the Fe protein was present in PP319, whereas neither form was detectable in the WT. Aerotolerant N2 fixation appears to be associated with the 32-kDa Fe protein in M. trichosporium OB3b.

Upper-mantle dynamics revealed by helium isotope variations along the southeast Indian ridge

Helium isotope variations in igneous rocks are important for relating isotopic heterogeneity to convective mixing in the Earth's mantle. High 3He/4He ratios at many ocean islands, along with lower and relatively uniform values in mid-ocean-ridge basalts (MORBs), are thought to result from a well mixed upper-mantle source for MORB and a distinct deeper-mantle source for ocean island basalts. At finer scales, 3He/4He variations along mid-ocean ridges have been related to underlying mantle heterogeneity, but relationships between the scales of geochemical segmentation and mantle convection remain enigmatic. Here we present helium isotope data for MORB glasses recovered along approximately 5,800 km of the southeast Indian ridge, and develop an approach to quantitatively relate spatial variations in geochemical and geophysical parameters at the Earth's surface. A point-to-point correlation analysis reveals structure in the helium isotope data at length scales of approximately 150 and approximately 400 km that appears to be related to secondary convection in the underlying mantle.

Copper-binding compounds from Methylosinus trichosporium OB3b

Two copper-binding compounds/cofactors (CBCs) were isolated from the spent media of both the wild type and a constitutive soluble methane monooxygenase (sMMOC) mutant, PP319 (P. A. Phelps et al., Appl. Environ. Microbiol. 58:3701-3708, 1992), of Methylosinus trichosporium OB3b. Both CBCs are small polypeptides with molecular masses of 1,218 and 779 Da for CBC-L1 and CBC-L2, respectively. The amino acid sequence of CBC-L1 is S?MYPGS?M, and that of CBC-L2 is SPMP?S. Copper-free CBCs showed absorption maxima at 204, 275, 333, and 356 with shoulders at 222 and 400 nm. Copper-containing CBCs showed a broad absorption maximum at 245 nm. The low-temperature electron paramagnetic resonance (EPR) spectra of copper-containing CBC-L1 showed the presence of a copper center with an EPR splitting constant between those of type 1 and type 2 copper centers (g = 2.087, g = 2.42 G, A = 128 G). The EPR spectrum of CBC-L2 was more complex and showed two spectrally distinct copper centers. One signal can be attributed to a type 2 Cu2+ center (g = 2.073, g = 2.324 G, A = 144 G) which could be saturated at higher powers, while the second shows a broad, nearly isotropic signal near g = 2.063. In wild-type strains, the concentrations of CBCs in the spent media were highest in cells expressing the pMMO and stressed for copper. In contrast to wild-type strains, high concentrations of CBCs were observed in the extracellular fraction of the sMMOC mutants PP319 and PP359 regardless of the copper concentration in the culture medium.

Isolation of copper biochelates from Methylosinus trichosporium OB3b and soluble methane monooxygenase mutants

Methylosinus trichosporium OB3b produces an extracellular copper-binding ligand (CBL) with high affinity for copper. Wild-type cells and mutants that express soluble methane monooxygenase (sMMO) in the presence and absence of copper (sMMOc) were used to obtain cell exudates that were separated and analyzed by size exclusion high-performance liquid chromatography. A single chromatographic peak, when present, contained most of the aqueous-phase Cu(II) present in the culture medium. In mutant cultures that were unable to acquire copper, extracellular CBL accumulated to high levels both in the presence and in the absence of copper. Conversely, in wild-type cultures containing 5 microM Cu(II), extracellular CBL was maintained at a low, steady level during exponential growth, after which the external ligand was rapidly consumed. When Cu(II) was omitted from the growth medium, the wild-type organism produced the CBL at a rate that was proportional to cell density. After copper was added to this previously Cu-deprived culture, the CBL and copper concentrations in the medium decreased at approximately the same rate. Apparently, the extracellular CBL was produced throughout the period of cell growth, in the presence and absence of Cu(II), by both the mutant and wild-type cultures and was reinternalized or otherwise utilized by the wild-type cultures when it was bound to copper. CBL produced by the mutant strain facilitated copper uptake by wild-type cells, indicating that the extracellular CBLs produced by the mutant and wild-type organisms are functionally indistinguishable. CBL from the wild-type strain did not promote copper uptake by the mutant. The molecular weight of the CBL was estimated to be 500, and its association constant with copper was 1.4 x 10(16) M-1. CBL exhibited a preference for copper, even in the presence of 20-fold higher concentrations of nickel. External complexation may play a role in normal copper acquisition by M. trichosporium OB3b. The sMMOc phenotype is probably related to the mutant's inability to take up CBL-complexed copper, not to a defective CBL structure.

Molecular typing of Helicobacter pylori isolates from a multicenter U.S. clinical trial by ureC restriction fragment length polymorphism

The molecular typing of 81 pretreatment Helicobacter pylori isolates and the comparison of 18 pretreatment-posttreatment pairs is described by restriction fragment length polymorphism (RFLP) of the ureC gene. The results of our study show the extreme genomic diversity of H. pylori and indicate that infection by H. pylori in the United States does not appear to be limited to a small number of RFLP types.

Lead and Helium Isotope Evidence from Oceanic Basalts for a Common Deep Source of Mantle Plumes

Linear arrays in lead isotope space for mid-ocean ridge basalts (MORBs) converge on a single end-member component that has intermediate lead, strontium, and neodymium isotope ratios compared with the total database for oceanic island basalts (OIBs) and MORBs. The MORB data are consistent with the presence of a common mantle source region for OIBs that is sampled by mantle plumes. 3He/4He ratios for MORBs show both positive and negative correlation with the 206Pb/204Pb ratios, depending on the MORB suite. These data suggest that the common mantle source is located in the transition zone region. This region contains recycled, oceanic crustal protoliths that incorporated some continental lead before their subduction during the past 300 to 2000 million years.

Mantle Plume Helium in Submarine Basalts from the Galápagos Platform

Helium-3/helium-4 ratios in submarine basalt glasses from the Galapagos Archipelago range up to 23 times the atmospheric ratio in the west and southwest. These results indicate the presence of a relatively undegassed mantle plume at the Galápagos hot spot and place Galápagos alongside Hawaii, Iceland, and Samoa as the only localities known to have such high helium-3/helium-4 ratios. Lower ratios across the rest of the Galápagos Archipelago reflect systematic variations in the degree of dilution of the plume by entrainment of depleted material from the asthenosphere. These spatial variations reveal the dynamics of the underlying mantle plume and its interaction with the nearby Galápagos Spreading Center.

Phenotypic characterization of copper-resistant mutants of Methylosinus trichosporium OB3b

Cultures of Methylosinus trichosporium OB3b grown in the presence of very low concentrations of copper synthesize a soluble methane monooxygenase (sMMO) that efficiently catalyzes the oxidation of trichloroethylene and other organic pollutants. Recently, we isolated five M. trichosporium OB3b mutants that express sMMO activity when grown in the presence of elevated copper concentrations (P.A. Phelps, S. K. Agarwal, G. E. Speitel, Jr., and G. Georgiou, Appl. Environ. Microbiol. 58:3701-3708, 1992). Here we show that, in contrast to the results for the wild-type cells, the addition of copper to mutant cultures grown on methane and nitrate as the nitrogen source has no noticeable effect on the growth rate and sMMO expression. In vitro experiments indicated that the copper-resistant phenotype does not arise from an increased stability of sMMO to copper deactivation. Furthermore, the mutant cultures exhibit altered speciation of copper in the extracellular fluid and have substantially decreased levels of cell-associated copper. On the basis of these results, we propose that the mutant phenotype arises from defects in copper uptake and metabolism rather than from changes in sMMO expression or enzyme stability.

Factors affecting competition between type I and type II methanotrophs in two-organism, continuous-flow reactors

Competition experiments were performed in a continuous-flow reactor using Methylosinus trichosporium OB3b, a type II methanotroph, and Methylomonas albus BG8, a type I methanotroph. The experiments were designed to establish conditions under which type II methanotrophs, which have significant cometabolic potential, prevail over type I strains. The primary determinants of species selection were dissolved methane, copper, and nitrate concentrations. Dissolved oxygen and methanol concentrations played secondary roles. M. trichosporium OB3b proved dominant under copper and nitratelimited conditions. The ratio of M. trichosporium to M. albus in the reactor increased ten-fold in less than 100 hours following the removal of copper from the reactor feed. Numbers of M. albus declined to levels that were below detection limits (<106/ml) under nitrogen-limited conditions. In the latter experiment, the competitive success of M. trichosporiumdepended on the maintenance of an ambient dissolved oxygen level below about 7.5 × 10(-5) M, or 30% of saturation with air. The ability of M. trichosporium to express soluble methane monooxygenase under copper limitation and nitrogenase under nitrate limitation was very significant. M. albus predominated under methane-limited conditions, especially when low levels of methanol were simultaneously added with methane to the reactor. The results imply that nitrogen limitation can be used to select for type II strains such as M. trichosporium OB3b.

Applications of a colorimetric plate assay for soluble methane monooxygenase activity

A straightforward method is described for screening methanotrophic colonies for soluble methane monooxygenase (sMMO) activity on solid media. Such activity results in the development of a colored complex between 1-naphthol, which is formed when sMMO reacts with naphthalene, and o-dianisidine (tetrazotized). Methanotrophic colonies expressing sMMO turned deep purple when exposed successively to naphthalene and o-dianisidine. The method was evaluated within the contexts of two potential applications. The first was for the enumeration of Methylosinus trichosporium OB3b in a methane-amended, unsaturated soil column dedicated to vinyl chloride treatment. The second application was for the isolation and enumeration of sMMO-bearing methanotrophs from sanitary landfill soils. The technique was effective in both applications.

Benzylated 1,2,3-triazoles as anticoccidiostats

Substituted 5-amino-4-carbamoyl-1,2,3-triazoles 3a-w were prepared by two synthetic schemes and evaluated in vivo for anticoccidial activity. Both schemes proceeded by brominating appropriately substituted toluenes 4a-s,v to 5a-s,v. In Scheme I, the brominated benzyl analogues 5 were converted to the corresponding benzyl azides 6, which were treated with cyanoacetamide to yield 1-substituted-5-amino-4-carbamoyl-1,2,3-triazoles 3. In Scheme II, the benzyl halides 5 were employed to alkylate the sodium salt of 5-amino-4-carbamoyl-1,2,3-triazole (7). Preliminary screening data against Eimeria acervulina and E. tenella in chickens suggested structural requirements for maximizing activity. Further evaluation against a relatively resistant series of eight Eimeria field isolates revealed L-651,582 (3a) to be a highly effective coccidiostat. However, unacceptable tissue residues precluded further development. Mechanistic studies on this series of 5-amino-4-carbamoyl-1,2,3-triazoles and, in particular, on L-651,582 (3a) revealed that its mode of action does not involve inhibition of IMP dehydrogenase, but probably interferes with host cell calcium entry. In addition, L-651,582 has been found to have antiproliferative activity in several disease models and was recently reported to possess antimetastatic activity in a model of ovarian cancer progression.

Inhibition of the mammalian beta-lactamase renal dipeptidase (dehydropeptidase-I) by (Z)-2-(acylamino)-3-substituted-propenoic acids

The title enzyme deactivates the potent carbapenem antibiotic imipenem in the kidney, producing low antibiotic levels in the urinary tract. A series of (Z)-2-(acylamino)-3-substituted-propenoic acids (3) are specific, competitive inhibitors of the enzyme capable of increasing the urinary concentration of imipenem in vivo. Many of the compounds were prepared in one step from an alpha-keto acid and a primary amide. The optimum R2 groups are 2,2-dimethyl, -dichloro, and -dibromocyclopropyl. With R2 = 2,2-dimethylcyclopropyl (DMCP), a wide variety of R3 groups including alkyl, oxa- and thiaalkyl, and alkyl groups containing acidic, basic, and neutral substituents give effective inhibitors with Ki values of 0.02-1 microM and a range of pharmacokinetic properties. By resolution of enantiomers and X-ray crystallography, the enzyme-inhibitory activity of the DMCP group was found to reside with the 1S isomer. The cysteinyl compound 176 (cilastatin, MK-0791) has the desired pharmacological properties and has been chosen for combination with imipenem.

Chemical and enzymatic properties of riboflavin analogues

The chemical and enzymatic properties of 26 analogues of riboflavin are presented. These analogues include both endo- and exocyclically substituted isoalloxazines with redox potentials from -370 to -128 mV. Physical and chemical data such as the electronic absorption spectra, pKas, and redox potentials of the analogues are presented and are discussed with respect to preferred tautomeric and resonance forms. Like riboflavin, most of the analogues are shown to be catalytic oxidants of dihydro-5-deazaflavins. Analogue binding to egg white binding apoprotein has been quantitated and serves to determine the origins of binding site specificity for this protein. Nearly all of the analogues that possess D-ribityl groups are found to be processed to the FAD level by the flavokinase/FAD synthetase system of Brevibacterium ammoniagenes. Most extensively studied are the reactivities of the analogues with the NAD(P)H:flavin oxidoreductase of Beneckea harveyi. Many of the analogues are substrates in this enzymatic redox reaction, and a linear free energy-rate relation (log Vmax vs. E0' of the analogue) is seen that parallels similar relationships in the nonenzymatic oxidation of dihydro-5-deazaflavins. This suggests a common mechanism for the reactions of such diverse flavins as riboflavin, 5-deazariboflavin, and 1-deazariboflavin.

Anticoccidial and tolerance studies in the chicken with two 6-amino-9-(substituted benzyl)purines

Initial assays of 6-amino-9-(2-chloro-6-fluorobenzyl) purine (MK-302) and 6-amino-9-(2,6-dichlorobenzyl)purine (coded L-628,914) showed potential as anticoccidial agents on the basis of broad-spectrum activity and safety. In battery efficacy studies, dietary levels of 60 to 70 p.p.m. and above MK-302 and 45 to 60 p.p.m. L-628,914 proved to have excellent broad-spectrum anticoccidial activity in chickens given heavy exposure to virulent field isolates of coccidia. Eight-week floor-pen tolerance trials showed that the maximum tolerated diet concentration (MTC) of MK-302 was approximately 95 p.p.m. while the MTC of L-628,914 was approximately 60 p.p.m. Dietary relationships (p.p.m. MK-302:p.p.m. L-628,914 for equivalent effects) derived from the efficacy and tolerance results were 1.2:1 and 1.6:1 respectively and clearly demonstrated a higher therapeutic ratio for MK-302.

Inhibitors of folate biosynthesis. 1. Inhibition of dihydroneopterin aldolase by pteridine derivatives

2-Amino-6-carboxamido-7,8-dihydropteridin-4-one and 2-amino-6-hydroxymethyl-7,7-dimethyl-7,8-dihydropteridin-4-one have been shown to be good inhibitors of Escherichia coli dihydroneopterin aldolase, an early enzyme of de novo folate biosynthesis.