The Destruction of Byssochlamys fulva asci by Low Concentrations of Gaseous Methyl Bromide and by Aqueous Solutions of Chlorine, an Iodophor and Peracetic Acid

S ummary : Byssochlamys fulva asci are resistant to high concentrations of aqueous chlorine and iodophor solutions, but are sensitive to peracetic acid. Concentrations of 2% and 4% of peracetic acid gave 99·9% reductions in 2·5 and 1·3 min, respectively. The asci were also sensitive to methyl bromide gas (MeBr), c. 5 × 10⁴ asci/g inoculated into tapioca starch powder ( a _w= 0·69) being killed in 30 days by 90 mg of MeBr/kg of starch. About 180 asci/g were killed by adding 60 mg of MeBr/kg of starch.     

Destruction of Toxic Fungi with Low Concentrations of Methyl Bromide

Aspergillus parasiticus and Penicillium rubrum spores at the level of 10(4) to 10(5) / g were completely killed by prolonged exposure to 30 to 45 mg of methyl bromide per liter.     

Utilization of Low Concentrations of Starch by a Flavobacterium Species Isolated from Tap Water

Experiments in well-cleaned glass flasks revealed that addition of starch in concentrations of 10 and 25 μg of substrate C per liter to the filtrate of slow sand filters stimulated the development of a yellow-pigmented bacterium which was identified as a Flavobacterium species. The isolate was able to multiply in tap water without substrates added, but addition of starch and glucose in amounts as low as 1 μg of substrate C per liter clearly enhanced growth. The substrate affinities of the Flavobacterium for these compounds were 3.9 μg of starch C and 3.3 μg of glucose C per liter. The results of this study indicate that microorganisms which rapidly utilize starch at a level of a few micrograms per liter commonly occur in water.     

Rehabilitation of Acidified Floating Fens by Addition of Buffered Surface Water

Floating fens are species‐rich succession stages in fen areas in the Netherlands. Many of these fens are deteriorating due to acidification; Sphagnum species and Polytrichum commune build 10–25 cm thick moss carpets, and the species diversity decreases. Earlier experiments in wet ecosystems indicate that successful restoration of circum‐neutral and mesotrophic conditions requires a combination of hydrological measures and sod removal. In an acidified fen recharged by rainwater in the nature reserve Ilperveld (The Netherlands), a ditch/trench system was dug for the purpose of creating a run‐off channel for acid rainwater in wet periods and to enable circum‐neutral surface water to enter the fen in dry periods. Moreover, the sod was removed in part of the fen. Ditch/trench creation or sod cutting had no effect individually, but a combination of the two measures led to a change in the abiotic conditions (higher pH and Ca), and in turn to an increase of species‐richness and the reestablishment of a number of characteristic species. Reestablishment of rare vascular plant species and characteristic bryophytes might be a long‐term process because of incomplete recovery of site conditions and constraints in seed dispersal.     

Growth of Aeromonas hydrophila at Low Concentrations of Substrates Added to Tap Water

The ability of an Aeromonas hydrophila isolate obtained from filtered river water to grow at low substrate concentrations was studied in batch experiments with tap water supplied with low concentrations of substrates. Growth was assessed by colony count determinations. The isolate only multiplied in the used tap water (2 to 3 mg of dissolved organic carbon per liter) after the addition of a small amount of an assimilable carbon compound. d-Glucose especially caused growth of the organism even at initial concentrations below 10 mug of C per liter. At initial glucose concentrations below the K(s) value (12 mug of C per liter), generation times and yield (colony-forming units per milligram of substrate-C) were nonlinear with 1/initial glucose concentrations and initial glucose concentrations, respectively. From these observations, the maintenance coefficient m was calculated (m = 0.015 mg of glucose per mg [dry wt] per h at 12 degrees C). At initial concentrations below the K(s) value of starch (73 mug of C per liter), no growth was observed, but complete use of starch occurred in these situations after the addition of 10 mug of glucose-C per liter. The results of this study show that information of ecological significance may be obtained by very simple batch experiments. Moreover, the isolate studied may be used in growth experiments to assess the maximum concentration of glucose which might be present in water, particularly tap water.     

Microbial Decomposer Communities Are Mainly Structured by Trophic Status in Circumneutral and Alkaline Streams

In streams, the release of nitrogen and phosphorus is reported to affect microbial communities and the ecological processes they govern. Moreover, the type of inorganic nitrogen (NO₃, NO₂, or NH₄) may differently impact microbial communities. We aimed to identify the environmental factors that structure aquatic microbial communities and drive leaf litter decomposition along a gradient of eutrophication. We selected five circumneutral (Portuguese) and five alkaline (French) streams differing in nutrient concentrations to monitor mass loss of alder leaves, bacterial and fungal diversity by PCR-denaturing gradient gel electrophoresis, fungal biomass and reproduction, and bacterial biomass during 11 weeks of leaf immersion. The concentrations of inorganic nutrients in the stream water ranged from 5 to 300 μg liter⁻¹ soluble reactive phosphorus, 0.30 to 5.50 mg liter⁻¹ NO₃-N, 2 to 103 μg liter⁻¹ NO₂-N, and <4 to 7,100 μg liter⁻¹ NH₄-N. Species richness was maximum in moderately anthropized (eutrophic) streams but decreased in the most anthropized (hypertrophic) streams. Different species assemblages were found in subsets of streams with different trophic statuses. In both geographic areas, the limiting nutrient, either nitrate or phosphate, stimulated the microbial activity in streams of intermediate trophic status. In the hypertrophic streams, fungal biomass and reproduction were significantly lower, and bacterial biomass dramatically decreased at the site with the highest ammonium concentration. The limiting nutrients that defined the trophic status were the main factor structuring fungal and bacterial communities, whatever the geographic area. A very high ammonium concentration in stream water most probably has negative impacts on microbial decomposer communities.There is evidence that increases in nitrate and phosphate concentrations stimulate microbial respiration and fungal and bacterial activity (biomass buildup, sporulation, and/or productivity) on plant litter, leading to faster leaf decomposition in freshwaters (16, 17, 26, 34). However, fungal demands of nitrate and phosphate are reported to be fulfilled at relatively low levels (1, 12), and further increases in these nutrients in the stream water do not necessarily result in enhanced fungal activity. Besides, the form in which inorganic nutrients are present in streams, their biological availability, and even their toxicity have different ecological consequences. In densely anthropized hypertrophic streams, high levels of nitrate and phosphate were associated with decreased fungal biomass and leaf breakdown, most probably because of the high concentrations of ammonium and ammonia (2). On the other hand, the positive effects of nutrients on biomass and productivity of leaf-associated fungi can be offset by other factors, such as low oxygen concentration and sedimentation, leading to retarded decomposition (26, 33, 34).Changes in inorganic nutrient concentrations in the stream water were reported to alter the structure of fungal communities on plant litter (16, 36). Nutrient additions to moderate levels increased the diversity of fungal communities in circumneutral soft-water Appalachian mountain streams (18) but not in a Mediterranean alkaline stream (1). Moreover, fungal diversity was lower in circumneutral eutrophic streams than in reference streams (10, 35). Fungal diversity has been assessed mostly through the morphological analysis of produced conidia, not taking into account nonsporulating fungi. This raises the question of whether the differential impacts of eutrophication on fungal diversity could be due partly to difficulties in measuring actual diversity. Besides, the study of bacterial diversity on decomposing leaves has been strongly restricted to a few cultivable bacteria (<1%). Molecular typing, such as denaturing gradient gel electrophoresis (DGGE) of a specific rRNA gene region, has proved useful for assessing diversity in both leaf-associated fungi and bacteria (7, 8, 9, 11, 30).We aimed to identify the environmental factors that drive the ecological processes in freshwaters impacted by eutrophication through examination of leaf litter decomposition and associated microbial communities along a gradient of nutrient enrichment. Specifically, we addressed the following two questions: (i) which are the environmental factors that mainly structure the fungal and bacterial communities and (ii) what are the relationships between concentrations of inorganic nutrients in the stream water, leaf litter decomposition, and the activity of associated microbes? We selected 10 stream sites spanning wide concentration ranges of dissolved inorganic nitrogen (NO₃-N, NO₂-N, NH₄-N, and NH₃-N) and soluble reactive phosphorus (SRP), including 5 in northwestern Portugal with circumneutral pH and 5 in southwestern France with an alkaline pH. With these two groups of stream sites, we assessed the structure of and diversity in both sporulating and nonsporulating fungal communities, using asexual spore morphology and DGGE fingerprints of the ITS2 region, and in bacterial communities, using DGGE fingerprints of the 16S rRNA gene region. Additionally, we examined leaf mass loss and microbial activity on decomposing leaves by determining bacterial and fungal biomass and fungal reproduction.     

Effect of Sorption on Mineralization of Low Concentrations of Aromatic Compounds in Lake Water Samples

Montmorillonite-benzylamine complexes were formed immediately upon addition of 20 pg to 20 μg of amine per ml of suspensions containing the clay. The extent of amine sorbed was a linear function of equilibrium amine concentration in lake water. Increases in the clay concentration decreased the percentage of the organic compound that was mineralized at amine levels of 20 pg to 200 ng, but not at 20 μg/ml. A larger percentage of the chemical was released from the complex during mineralization in the presence of high clay concentrations than in the presence of low clay concentrations. The rates of desorption and mineralization increased linearly with benzylamine levels up to 200 ng/ml. Montmorillonite did not enhance mineralization rates at amine levels of 200 ng/ml or lower, but it was stimulatory at 20 μg/ml. Except at high amine and clay concentrations, mineralization was more rapid than desorption during the early periods of decomposition when the amine concentration in solution was relatively high. However, relative to the microbial demand, desorption was more rapid during later periods of decomposition when the amine level in solution was very low. Mineralization of benzoate was not usually affected by montmorillonite, kaolinite, or glass beads. More than 90% of the carbon from benzylamine and benzoate was often mineralized when the substrate concentration was 250 ng/ml or less. After incubation of the chemical in lake water, none of the radioactivity from benzylamine was in the particulate fraction containing natural sediment and microbial cells. The data indicate that clay may have a significant effect on the microbial decomposition of low concentrations of certain organic compounds.     

Anoxic Biodegradation of Isosaccharinic Acids at Alkaline pH by Natural Microbial Communities

One design concept for the long-term management of the UK’s intermediate level radioactive wastes (ILW) is disposal to a cementitious geological disposal facility (GDF). Under the alkaline (10.0<pH>13.0) anoxic conditions expected within a GDF, cellulosic wastes will undergo chemical hydrolysis. The resulting cellulose degradation products (CDP) are dominated by α- and β-isosaccharinic acids (ISA), which present an organic carbon source that may enable subsequent microbial colonisation of a GDF. Microcosms established from neutral, near-surface sediments demonstrated complete ISA degradation under methanogenic conditions up to pH 10.0. Degradation decreased as pH increased, with β-ISA fermentation more heavily influenced than α-ISA. This reduction in degradation rate was accompanied by a shift in microbial population away from organisms related to Clostridium sporosphaeroides to a more diverse Clostridial community. The increase in pH to 10.0 saw an increase in detection of Alcaligenes aquatilis and a dominance of hydrogenotrophic methanogens within the Archaeal population. Methane was generated up to pH 10.0 with acetate accumulation at higher pH values reflecting a reduced detection of acetoclastic methanogens. An increase in pH to 11.0 resulted in the accumulation of ISA, the absence of methanogenesis and the loss of biomass from the system. This study is the first to demonstrate methanogenesis from ISA by near surface microbial communities not previously exposed to these compounds up to and including pH 10.0.     

Microbial Diversity in a Permanently Cold and Alkaline Environment in Greenland

The submarine ikaite columns located in the Ikka Fjord in Southern Greenland represent a unique, permanently cold (less than 6°C) and alkaline (above pH 10) environment and are home to a microbial community adapted to these extreme conditions. The bacterial and archaeal community inhabiting the ikaite columns and surrounding fjord was characterised by high-throughput pyrosequencing of 16S rRNA genes. Analysis of the ikaite community structure revealed the presence of a diverse bacterial community, both in the column interior and at the surface, and very few archaea. A clear difference in overall taxonomic composition was observed between column interior and surface. Whereas the surface, and in particular newly formed ikaite material, was primarily dominated by Cyanobacteria and phototrophic Proteobacteria, the column interior was dominated by Proteobacteria and putative anaerobic representatives of the Firmicutes and Bacteroidetes. The results suggest a stratification of the ikaite columns similar to that of classical soda lakes, with a light-exposed surface inhabited by primary producers and an anoxic subsurface. This was further supported by identification of major taxonomic groups with close relatives in soda lake environments, including members of the genera Rhodobaca, Dethiobacter, Thioalkalivibrio and Tindallia, as well as very abundant groups related to uncharacterised environmental sequences originally isolated from Mono Lake in California.     

In Situ Exposure to Low Herbicide Concentrations Affects Microbial Population Composition and Catabolic Gene Frequency in an Aerobic Shallow Aquifer

The aim of this study was to evaluate how the in situ exposure of a Danish subsurface aquifer to phenoxy acid herbicides at low concentrations (<40 μg l⁻¹) changes the microbial community composition. Sediment and groundwater samples were collected inside and outside the herbicide-exposed area and were analyzed for the presence of general microbial populations, Pseudomonas bacteria, and specific phenoxy acid degraders. Both culture-dependent and culture-independent methods were applied. The abundance of microbial phenoxy acid degraders (10⁰ to 10⁴ g⁻¹ sediment) was determined by most probable number assays, and their presence was only detected in herbicide-exposed sediments. Similarly, PCR analysis showed that the 2,4-dichlorophenoxyacetic acid degradation pathway genes tfdA and tfdB (10² to 10³ gene copies g⁻¹ sediment) were only detected in sediments from contaminated areas of the aquifer. PCR-restriction fragment length polymorphism measurements demonstrated the presence of different populations of tfd genes, suggesting that the in situ herbicide degradation was caused by the activity of a heterogeneous population of phenoxy acid degraders. The number of Pseudomonas bacteria measured by either PCR or plating on selective agar media was higher in sediments subjected to high levels of phenoxy acid. Furthermore, high numbers of CFU compared to direct counting of 4′,6-diamidino-2-phenylindole-stained cells in the microscope suggested an increased culturability of the indigenous microbial communities from acclimated sediments. The findings of this study demonstrate that continuous exposure to low herbicide concentrations can markedly change the bacterial community composition of a subsurface aquifer.     

Isolation and Crystallization of Microbial Alkaline Protease Inhibitor,S-SI

S–SI, an microbial alkaline protease inhibitor, was produced in the culture broth of Streptomyces albogriseolus S–3253. S–SI was isolated from culture filtrate by salting out with ammonium sulfate, column chromatographies on DEAE-cellulose and Sephadex G–100. S–SI was also isolated by pH adjustment of the effluent from DEAE-cellulose column.

Crystallization of S–SI was carried out, and two distinct shaped crystals, needle shaped and rhombic crystal, were obtained. Homogeneity of these crystals were identified by polyacrylamide disc electrophoresis at various pHs.

S–SI retained its perfect inhibitory activity after treatment at 37°C for 25 hr in the pH range from 3 to 10, and 100°C for 10 min in the pH range from 4 to 6.

From the examination of molecular weight determination with Sephadex G–100, the molecular weight of S–SI was decided to be about 27,000.

S–SI was found to be highly specific towards microbial alkaline proteases.     

Rapid Consumption of Low Concentrations of Methyl Bromide by Soil Bacteria

A dynamic dilution system for producing low mixing ratios of methyl bromide (MeBr) and a sensitive analytical technique were used to study the uptake of MeBr by various soils. MeBr was removed within minutes from vials incubated with soils and ~10 parts per billion by volume of MeBr. Killed controls did not consume MeBr, and a mixture of the broad-spectrum antibiotics chloramphenicol and tetracycline inhibited MeBr uptake by 98%, indicating that all of the uptake of MeBr was biological and by bacteria. Temperature optima for MeBr uptake suggested a biological sink, yet soil moisture and temperature optima varied for different soils, implying that MeBr consumption activity by soil bacteria is diverse. The eucaryotic antibiotic cycloheximide had no effect on MeBr uptake, indicating that soil fungi were not involved in MeBr removal. MeBr consumption did not occur anaerobically. A dynamic flowthrough vial system was used to incubate soils at MeBr mixing ratios as low as those found in the remote atmosphere (5 to 15 parts per trillion by volume [pptv]). Soils consumed MeBr at all mixing ratios tested. Temperate forest and grassy lawn soils consumed MeBr most rapidly (rate constant [k] = 0.5 min⁻¹), yet sandy temperate, boreal, and tropical forest soils also readily consumed MeBr. Amendments of CH₄ up to 5% had no effect on MeBr uptake even at CH₄:MeBr ratios of 10⁷, and depth profiles of MeBr and CH₄ consumption exhibited very different vertical rate optima, suggesting that methanotrophic bacteria, like those presently in culture, do not utilize MeBr when it is at atmospheric mixing ratios. Data acquired with gas flux chambers in the field demonstrated the very rapid in situ consumption of MeBr by soils. Uptake of MeBr at mixing ratios found in the remote atmosphere occurs via aerobic bacterial activity, displays first-order kinetics at mixing ratios from 5 pptv to ~1 part per million per volume, and is rapid enough to account for 25% of the global annual loss of atmospheric MeBr.     

Transformation of Low Concentrations of 3-Chlorobenzoate by Pseudomonas sp. Strain B13: Kinetics and Residual Concentrations

The transformation of 3-chlorobenzoate (3CB) and acetate at initial concentrations in the wide range of 10 nM to 16 mM was studied in batch experiments with Pseudomonas sp. strain B13. Transformation rates of 3CB at millimolar concentrations could be described by Michaelis-Menten kinetics (K(infm), 0.13 mM; V(infmax), 24 nmol (middot) mg of protein(sup-1) (middot) min(sup-1)). Experiments with nanomolar and low micromolar concentrations of 3CB indicated the possible existence of two different transformation systems for 3CB. The first transformation system operated above 1 (mu)M 3CB, with an apparent threshold concentration of 0.50 (plusmn) 0.11 (mu)M. A second transformation system operated below 1 (mu)M 3CB and showed first-order kinetics (rate constant, 0.076 liter (middot) g of protein(sup-1) (middot) min(sup-1)), with no threshold concentration in the nanomolar range. A residual substrate concentration, as has been reported for some other Pseudomonas strains, could not be detected for 3CB (detection limit, 1.0 nM) in batch incubations with Pseudomonas sp. strain B13. The addition of various concentrations of acetate as a second, easily degradable substrate neither affected the transformation kinetics of 3CB nor induced a detectable residual substrate concentration. Acetate alone also showed no residual concentration (detection limit, 0.5 nM). The results presented indicate that the concentration limits for substrate conversion obtained by extrapolation from kinetic data at higher substrate concentrations may underestimate the true conversion capacity of a microbial culture.     

Low Concentrations of Trifluoperazine Affect Striatal Cells in Culture

Abstract: Primary monolayer cultures of the newborn rat corpus striatum were treated with the phenothiazine trifluoperazine after various times in culture. When the drug is added to cells at least 3 weeks old, concentrations of 10⁻⁷ and 10⁻⁸ M appear morphologically identical to controls but show significant changes in synthesis of acetylcholine and γ-aminobutyric acid, particularly the former. The results with these very low concentrations suggest that the drug has a highly specific effect directly on striatal cells, and that it is not acting via calmodulin.     

分子生物学方法在水体微生物生态研究中的应用

微生物是生态系统的重要组成部分,研究水体中微生物的多样性和群落结构对于开发微生物资源、进行水体生物修复具有重要意义。现代分子生物学的发展为研究水体微生物提供了行之有效的方法。综述了16S rDNA文库构建、变性梯度凝胶电泳、限制性片段长度多态性、末端标记限制性片段长度多态性等技术的原理以及在水体微生物研究中的主要应用。     

Induced Activity of Superoxide Dismutase and Peroxidase of in vitro Plants by Low Concentrations of Ethanol

A rapid micropropagation protocol was established for Aloe vera L. var. chinensis (Haw.) Berger, Chinese Aloe. The effects of three factors, namely BA, NAA and sucrose, on bud initiation were evaluated by L₉ (3⁴) orthogonal design. The variance analysis of the experimental results showed that the actions of the three factors were all considerable. Among the three factors, sucrose was the most important for bud initiation followed by BA, and NAA had the weakest effect. The best medium for bud initiation was semi-solid MS supplemented with 2.0 mg l^–1 BA, 0.3 mg l^–1 NAA, 30 g l^–1 sucrose and 0.6 g l^–1 PVP (pH 5.8), on which Chinese aloe could multiply 15 times in 4 weeks. Some shoots rooted spontaneously on 1/2 strength MS medium, but the rooting percentage was improved in the presence of 0.2 mg l^–1 NAA. Rooted plantlets were acclimatized to greenhouse conditions. The young plantlets from tissue culture were transplanted successfully. In vitro propagation can be a useful tool in the conservation of this endangered medicinal species.     

Citric Acid Fermentation by Aspergillus niger on Low Sugar Concentrations and Cotton Waste

The possible use of cotton waste as a carbohydrate source of citric acid production by Aspergillus niger was examined. No citric acid was produced when A. niger was grown on cotton waste as a sole carbon source. In two-stage fermentations, however, mycelium obtained from surface cultures in cotton waste medium yielded more citric acid when transferred to sucrose-containing media than when directly inoculated to sucrose-containing media. It is concluded that cotton waste can be used for saving sucrose and for increasing yields of citric acid fermentation by A. niger.     

低浓度NaHSO3促进田间水稻的光合磷酸化和光合作用

用1～2 mmol/L NaHSO3喷施于水稻(Oryza sativa L.)叶面可以提高叶片的光合速率,并能持续3 d以上.在此条件下,光下叶片中的ATP含量明显增高,叶片的叶绿素毫秒延迟荧光加强,反映与光合磷酸化活力有关的跨类囊体膜质子梯度增加.乳熟期喷施2次1 mmol/L NaHSO3后,水稻产量提高约10%.研究表明NaHSO3的主要作用和PMS(phenazine methosulfate)促进光合速率的原因可能类似,都是增加了ATP的供应.与此同时,观察到低浓度NaHSO3可促进水稻中反映循环电子传递的叶绿素荧光在作用光关闭后的短时上升.以上现象表明低浓度NaHSO3的促进作用很可能是通过促进围绕PSⅠ的循环电子传递及其耦联的光合磷酸化而促进水稻光合作用的.     

低浓度NaHSO3促进田间水稻的光合磷酸化和光合作用

用１～２ｍｍｏｌ／Ｌ ＮａＨＳＯ３喷施于水稻（Ｏｒｙｚａ ａｔｉｖａ Ｌ．）叶面可以提高叶片的光合速率,并能持续３ｄ以上。在此条件下,光下叶片中的ＡＴＰ含量明显增高,叶片的叶绿素毫秒延迟荧光加强,反映与光合磷酸化活力有关的跨类囊体膜质子梯度增加。乳熟期喷施２次１ｍｍｏｌ／Ｌ ＮａＨＳＯ３后,水稻产量提高约１０％。研究表明ＮａＨＳＯ３的主要作用和ＰＭＳ（ｐｈｅｎａｚｉｎｅ ｍｅｔｈｏｓｕｌｆａｔｅ）