Arsenic resistant microorganisms isolated from agricultural drainage water and evaporation pond sediments

Elevated levels of As in contaminated water and soil could pose a major threat to the environment. Relatively high levels of As have been reported in agricultural drainage water and in evaporation pond sediments in Kern County, California. The objective of this study was to enumerate and isolate As-resistant microorganisms from agricultural drainage water and evaporation pond sediments and to assess their tolerance to metals, metalloids and antibiotics. The culture medium was amended with arsenite (III), arsenate (V), methylarsonic acid (MAA), and dimethylarsinic acid (DMA). Among the water samples, As(V), MAA, and DMA added to the medium at concentrations from 0.1 to 1000 mg L^?1 showed no effect on the colony forming units (CFUs) compared with no As supplementation, while arsenite (III) (> 1.0 mg L^?1) inhibited the population. The sediments showed three trends: (i) no effect on CFUs in the presence of As(V) up to 1000 mg kg^?1, (ii) a decline in CFUs in the presence of > 100 mg kg^?1, As(III), and (iii) an increase in CFUs upon the addition of MAA or DMA at > 25 mg kg^?1, Arsenite (III) was much more toxic to the indigenous microflora than any other As species. Arsenite (III) inactivates many enzymes by having a high affinity for thiol groups of proteins. A plate diffusion method was used to assess the tolerance of the As-resistant bacteria to heavy metals, metalloids and antibiotics. Of 14 isolates tested, all were resistant to Co, Cu, Pb, Ni, Mo, Cr, Se(IV), Se(VI), As(III), As(V), Sb, Sn, and Ag (50 µg mL^?1). The most toxic trace elements were Cd followed by Hg>Te>Zn. Multiple antibiotic tolerance (resistance to 2 or more antibiotics) was found among 43% of the isolates. The As-resistant bacteria showed a high tolerance to metals and antibiotics.     

Occurrence of 12-methyltridecanal in microorganisms and physiological samples isolated from beef

12-Methyltridecanal (MT) smelling tallowy, beef-like was formed from plasmalogens when beef was boiled. To clarify the origin of MT, its concentration was determined by a stable isotope dilution assay in bacteria and protozoa isolated from the rumen of bovine animals as well as in the plasma, erythrocytes, and other physiological samples. The highest amounts of MT were found in bacteria followed by protozoa. The MT content of the erythrocytes was small. The results support the hypothesis that microorganisms are the main source of MT of which a small amount is resorbed by the animal and transported to the muscular tissue where MT is incorporated into plasmalogens.     

Antimicrobial activity of olive solutions from stored Alpeorujo against plant pathogenic microorganisms

The aim of this work was to assess the in vitro antimicrobial effects that wastewaters from alpeorujo oil extraction have against phytopathogenic bacteria and fungi. Alpeorujo was stored for 6 months and then processed to extract its oil, pomace, and a new liquid waste (OWSA), which was characterized by its content in phenolic compounds. OWSA at 20% decreased bu >4 log the population of Erwinia spp., Pseudomonas spp., and Clavibacter spp. viable cells in test tubes, whereas OWSA at 50% in agar medium was necessary to inhibit mycelial growth of most fungi. It was found that the bactericidal effect was due to the joint action of low molecular mass phenolic compounds, although neither hydroxytyrosol, its glucosides, hydroxytyrosol glycol, nor a glutaraldehyde-like compound individually explained this bioactivity. Hence, OWSA constitutes a promising natural solution to fight plant phytopathogenic bacteria and fungi.     

矿区植物根内嗜鱼外瓶霉对重金属的耐性和超积累作用

从云南会泽铅-锌矿区自然生长植物密序野古草(Arundinella bengalensis(Spreng.)Druce)的健康根内分离得到一株深色有隔内生真菌(dark septate endophytes,DSE)。据其形态学特征和ITS1-5.8S-rDNA-ITS2序列分析,鉴定为一株嗜鱼外瓶霉(Exophiala pisciphila)。纯培养条件下研究了其对Pb2+、Zn2+、Cd2+的耐性和超积累作用。结果表明,此菌株在液体合成培养基上可以分别耐受2、3和0.5 g/L的Pb2+、Zn2+和Cd2+;在含Pb2+、Cd2+培养基中生长其菌丝可以富集超过其干重25%以上的Pb2+和5%以上的Cd2+;显示此菌株属于极端耐性并具有超积累作用的真菌。此真菌在植物根系的定殖或许可以通过菌丝体对金属离子的固持作用缓解植物根围土壤微环境中超量金属离子对植物的毒害作用。     

Travel of microorganisms from a septic tile

An investigation was carried out to monitor the horizontal travel of indicator microorganism from the end of a septic tile in the direction of groundwater flow. The microorganism levels exhibited a declining trend with distance away from the tile end. This investigation also revealed that because the unsaturated depth of soil available for microorganism vertical travel was limited, relatively high levels of organisms were found in the groundwater even at a horizontal distance of 15.25 m from the end of the septic tile.     

微生物在植物铁营养中的潜在作用

根据近十多年来相关研究成果讨论了土壤微生物在植物根系吸收铁中可能的作用机理。这种机理可能包括缺铁植物根系分泌小分子有机化合物,如酚类和黄素类等化合物,这些化合物作为抑菌剂和(或)作为微生物生长的碳源物质来影响根际(Rhizosphere)微生物的群落结构,并在植物根际诱导形成特异性微生物种群,此类特异性微生物转而通过分泌高铁载体(Siderophore),增加土壤中铁的生物有效性,从而提高了根系对铁的吸收。此外,与植物根系共生的一些微生物也会改善植物的铁营养,这种作用可能包括:根瘤菌(Rhizobium)的结瘤作用,增强植物耐缺铁的生理响应;根系感染的菌根真菌通过增加植物根系的养分吸收面积和分泌对铁具有螯合作用的物质来改善植物的铁营养。本文在讨论这种可能的微生物作用机制的基础上,指出今后的研究方向和有待解决的问题。     

Effects of airborne emissions from a natural gas processing plant on the production of swine

Specific-pathogen-free swine were produced under field conditions in a high emission exposure area and a low emission exposure area of a natural gas processing plant over a period of 38 mo. Production parameters were measured and respiratory tissues sampled. Sulfur dioxide concentration was monitored in the high exposure area. Average concentrations of SO₂ exceeded 0.20 ppm for 30 min on 23 occasions during one of four rate of gain and feed conversion trials. Average concentrations of SO₂ exceeded 0.02 ppm for 24 hr on 5 days when farrowings occurred. No significant difference was found in rate of gain, feed conversion, piglets born per litter or piglet survival, between swine produced in the two areas. No histological a alterations such as loss of cilia, atrophy of goblet cells or cellular metaplasia were observed in any respiratory epithelia from 62 pigs.     

Soil application of insecticides influences microorganisms and plant nutrients

An experiment was conducted under laboratory conditions to investigate the effect of four insecticides, viz. HCH, phorate, carbofuran and fenvalerate at their field application rates (7.5, 1.5, 1.0 and 0.35 kg a.i. ha⁻¹, respectively), on the growth and development of bacteria, actinomycetes and fungi as well as their role in the transformations and availability of some plant nutrients in laterite soil (Typic Orchragualf). All the insecticides in general, and HCH and phorate in particular, significantly increased the population of microorganisms in soil. The most predominant genera of microorganisms, such as Bacillus, Micrococcus and Aspergillus were not affected by most of the insecticides. However, some of the insecticides stimulated the growth and development of Bacillus, Proteus, Corynebacterium, Streptomyces, Fusarium, Trichoderma and Rhizopus. On the other hand, some insecticide exerted deleterious effect on the proportions of Pseudomonas, Staphylococcus, Nocardia, Micromonospora, Aspergillus and Rhizopus. Incorporation of insecticides also significantly stimulated the mineralization and availability of organic C, N and P in soil. Among the tested substances, the stimulations were more pronounced with HCH followed by phorate and fenvalerate.     

Copper uptake studies on Erica andevalensis,a metal‐tolerant plant from southwestern Spain

Abstract

Pot trials and chemical analyses were carried out on wild specimens of Erica andevalensis Cabezudo et Rivera (Ericaceae) and their associated soils. Natural soils hosting E. andevalensis all had elevated copper concentrations. Pot trials showed that the Erica would grow in sulphide‐ore substrates containing up to 12,500 μg g^‐1 (1.25%) copper, with or without amendment with EDTA. The addition of EDTA to these substrates increased the solubility of the copper to levels that killed other metal‐tolerant species (Biscutella laevigata and Brassica juncea), but not E. andevalensis. The copper concentrations in wild plants were only 1 to 24 μg g^‐1 (dry weight) despite the high levels of copper (up to 3,676 μg g^‐1) in the supporting soils. In the pot trials, the plant was able partially to exclude total copper up to 1,000 μg g^‐1 in the soil. Thereafter, there was an exponential increase of copper in plant until the limit of tolerance was reached. Conclusions of the study were: (a) tolerance to copper by the Erica is much higher compared with other metal‐tolerant plants tested, (b) the plant does not have hyperaccumulator status (> 1,000 μg g^‐1 dry weight) for copper, (c) copper uptake by the plant is governed by the extractable and not total copper content of the soil, hence limiting its use in biogeochemical prospecting, (d) uptake of copper by the plant follows the typical pattern of a metal‐excluding plant, (e) Erica andevalensis is a good geobotanical indicator of copper because of its faithful association with sulphide mineralization in the Huelva area of Spain.     

Effect of climate on plant evaporation coefficients for the potato crop

The plant evaporation coefficient, k_vm, is defined as the ratio of upper limit plant evaporation to reference crop (short grass surface) evaporation. Variations in k_vm for a potato crop were shown to be due to the combined and varying influence of water vapour pressure, ambient temperature, radiation and wind speed. A multiple linear regression model for predicting k_vm from these weather elements was developed. The coefficient of determination (r₂) was 0.81 significant at the 0.1% confidence level, with a standard error of estimate of 0.19. Climatic adjustments to evaporation coefficients for other field crops, were also proposed.     

Phosphate solubilizing microorganisms isolated from rhizosphere of maize cultivated in an oxisol of the Brazilian Cerrado Biome

Many soil microorganisms are able to transform insoluble forms of phosphorus to an accessible soluble form, contributing to plant nutrition as plant growth-promoting microorganisms (PGPM). The objective of this work was to isolate, screen and evaluate the phosphate solubilization activity of microorganisms in maize rhizosphere soil to manage soil microbial communities and to select potential microbial inoculants. Forty-five of the best isolates from 371 colonies were isolated from rhizosphere soil of maize grown in an oxisol of the Cerrado Biome with P deficiency. These microorganisms were selected based on the solubilization efficiency of inorganic and organic phosphate sources in a modified Pikovskaya's liquid medium culture containing sodium phytate (phytic acid), soybean lecithin, aluminum phosphate (AlPO₄), and tricalcium phosphate (Ca₃(PO₄)₂). The isolates were identified based on nucleotide sequence data from the 16S ribosomal DNA (rDNA) for bacteria and actinobacteria and internal transcribed spacer (ITS) rDNA for fungi. Bacteria produced the greatest solubilization in medium containing tricalcium phosphate. Strains B17 and B5, identified as Bacillus sp. and Burkholderia sp., respectively, were the most effective, mobilizing 67% and 58.5% of the total P (Ca₃(PO₄)₂) after 10 days, and were isolated from the rhizosphere of the P efficient L3 maize genotype, under P stress. The fungal population was the most effective in solubilizing P sources of aluminum, phytate, and lecithin. A greater diversity of P-solubilizing microorganisms was observed in the rhizosphere of the P efficient maize genotypes suggesting that the P efficiency in these cultivars may be related to the potential to enhance microbial interactions of P-solubilizing microorganisms.     

The wetland plant and macroinvertebrate assemblages of temporary ponds in England and Wales

The biodiversity value of Northern European temporary ponds has been little recognised, and there are many gaps in our understanding of their ecology. This study investigated the wetland (including aquatic) plant and macroinvertebrate assemblages, and the physico-chemical characteristics of 71 temporary ponds in semi-natural habitats. Temporary ponds supported on average 17 (SD ± 8) wetland plant and 25 (SD ± 10) macroinvertebrate species. Over 75% of temporary ponds supported at least one uncommon (local, nationally scarce or Red Data Book) species. The number of uncommon wetland plant species and total number of macroinvertebrate species were both positively correlated with the total number of wetland plant species (richness), but there was no correlation between the number of uncommon and common macroinvertebrate species. Almost three-quarters of temporary ponds supported at least one nationally scarce macroinvertebrate and 8% supported at least one nationally scarce plant across a wide range of physico-chemical characteristics. The main environmental factor influencing the composition of temporary pond communities was water chemistry, particularly pH and alkalinity. The occurrence of facultative as well as obligate temporary pond species suggested that this habitat may play an important role in the interchange of species between waterbodies at the landscape scale.     

Multifaceted beneficial effects of rhizosphere microorganisms on plant health and productivity

Plant growth promoting microorganisms (PGPM) and biological control agents (BCA) are shown to possess secondary beneficial effects that would increase their usefulness as bio-inoculants, regardless of the need for their primary function. Indeed, PGPM, such as Rhizobium and Glomus spp., can promote plant growth and productivity (primary effect) but have now been shown to also play a role in reducing disease (secondary effect). Conversely, BCA, such as Trichoderma and Pseudomonas spp., can control disease (primary effect) but have recently demonstrated stimulation of plant growth (secondary effect) in the absence of a pathogen. Further work shedding light onto the precise mode of action and ecophysiology of these microorganisms would assist with their timely and appropriate use and potentially unleash their full promise as beneficial rhizosphere bio-inoculants for improved growth and health of plants. The potential increased use of these microorganisms afforded by their multifaceted beneficial effects may further help in reducing problems associated with the use of synthetic chemicals in agriculture.     

Airborne heavy metal pollution in the environment of a danish steel plant

A survey of heavy metal deposition was carried out in the vicinity of a Danish steel plant. Bulk precipitation and transplanted lichen (Hypogymnia physodes (L.) Nyl.) were sampled at 12 stations in the environment before and after the production had been converted from open-hearth furnaces to electric-arc furnaces. The samples were analyzed for Cd, Cr, Cu, Fe, Mn, Pb and Zn. The results show that heavy metal pollution from the steelworks still is severe and that it follows a decreasing power curve when the distance to the steelworks is increased. However, a reduction in the deposition of heavy metals close to the steelworks has been observed, pointing to the conclusion that the change from a situation of emission through a 46 m stack without any filter to emission from the electric arc furnaces equipped with bag-filters has lead to changes in the emission. At the sampling stations with the highest deposition levels measured in bulk precipitation the corresponding concentrations in the lichens were relatively lower indicating a change in particle size distribution. Within each station there was a direct proportionality of metal concentrations in lichens and atmospheric fallout measured in bulk precipitation.     

Significance of organic nitrogen uptake from plant residues by soil microorganisms as affected by carbon and nitrogen availability

Soil microorganisms can use a wide range of nitrogen (N) compounds. When organic N sources are degraded, microorganisms can either take up simple organic molecules directly (direct route), or organic N may be mineralized first and taken up in the form of mineral N (mineralization-immobilization-turnover [MIT] route). To determine the importance of the direct route, a microcosm experiment was carried out. Two types of wheat residue were added to soil samples, including younger residue with a carbon (C) to N ratio of 12 and older residue with a C to N ratio of 29. Between days 1 and 4, the gross N mineralization rate reached 8.4 and 4.0 mg N kg⁻¹ dry soil day⁻¹ in the treatment with younger and older residue, respectively. During the same period, there was no difference in protease activity between the two residue amended treatments. The fact that protease activity was not related to gross N mineralization, even though the products of protease activity are the substrates for N mineralization, suggests that not all organic molecules released from residue or soil N passed through the soil mineral N pool. In fact, when leucine and glycine were added, only 10 and 53% of the amino acid-N, respectively, was mineralized. The fraction of N taken up via the direct route was estimated to be 55 and 62% for the young and older residue, respectively. After 28 days of incubation, the proportion of amino acid-N mineralized had increased especially in the soil amended with older residue, suggesting that the MIT route became increasingly important. This result is supported by an increase in the activities of enzymes responsible for the intracellular assimilation of ammonium (NH₄⁺). Our results suggest that in contrast to what is proposed by many models of soil N cycling, both the direct and MIT routes were operative, with the direct route being the preferred route of residue N uptake. The direct route became less important over time and was more important in soil amended with older residue, suggesting that the direct route is favored by lower mineral N availabilities. An important implication of these findings is that when the direct route is dominant, gross N mineralization underestimates the amount of N made available from the residue.     

番茄内生菌102菌株的促生作用研究

通过种子发芽、小麦芽鞘切断伸长、盆栽及微区试验对番茄内生菌102的促生作用进行测定。结果表明：经102菌稀释液处理的青菜、番茄种子的发芽率及根长显著提高；同样，稀释50至200倍的102菌发酵液可以促进小麦芽鞘切断的仲长，增长率达11％以上；盆栽结果表明使用102菌可以提高青菜和菠菜的鲜重达36％、19％，株高、叶数、叶宽、叶长等各项指标也均显著提高；微区试验结果：经102菌处理的青菜产量比对照增加39％，单株鲜重增加30％，差异达极显著水平；以上结果表明102菌促生作用明显。     

番茄内生菌102菌株的促生作用研究

通过种子发芽、小麦芽鞘切断伸长、盆栽及微区试验对番茄内生菌102的促生作用进行测定。结果表明:经102菌稀释液处理的青菜、番茄种子的发芽率及根长显著提高;同样,稀释50至200倍的102菌发酵液可以促进小麦芽鞘切断的伸长,增长率达11%以上;盆栽结果表明使用102菌可以提高青菜和菠菜的鲜重达36%、19%,株高、叶数、叶宽、叶长等各项指标也均显著提高;微区试验结果:经102菌处理的青菜产量比对照增加39%,单株鲜重增加30%,差异达极显著水平;以上结果表明102菌促生作用明显。     

Soil microorganisms and the growth of Lupinus albus on a high metal soil in the presence of EDTA

A pot experiment was designed with the objective of determining whether the presence of ethylenediaminetetraacetic acid (EDTA) and the resulting mobilization of heavy metals have any affect on: (i) soil microorganisms, (ii) growth of L. albus, and (iii) microbial colonization of roots. There was no effect of the different treatments on the contents of soil microbial biomass C and microbial biomass N. Increasing addition of EDTA to soil led to proportionate increases in extractable C and N, being roughly equivalent to the added amount. Increasing EDTA addition to soil led also to a proportionate increase in mobile heavy metals. Plant height, total amount of shoot and root C were not affected by EDTA addition. Fungal ergosterol in the lupine roots showed a 5- to 8-fold increase in the 0.1 and 0.2% EDTA treatments in comparison with the control. In contrast, EDTA addition did not affect fungal glucosamine or bacterial muramic acid concentrations in the lupine roots. Increasing EDTA addition to soil led also to a proportionate increase in the metal concentrations in the lupine shoots. The concentrations of heavy metals in the lupine shoots and in the NH₄NO₃ soil extracts were all highly significantly correlated.