Nocardiopsis compostus sp. nov., from the atmosphere of a composting facility.
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Three strains (KS8, KS9T and KS21), isolated from air samples near a composting facility, were subjected to taxonomic analyses (characterized using a polyphasic approach). Morphological and chemotaxonomic characteristics of the isolates were in agreement with those described for members of the genus Nocardiopsis. On the basis of 16S rRNA sequence comparison and phenotypic tests, KS21 clearly belonged to Nocardiopsis alba. KS8 and KS9T showed less than 98% 16S rRNA gene sequence similarity to any of the previously described Nocardiopsis species. The polar lipid profiles of both isolates consisted of four major compounds, phosphatidylmonomethylethanolamine, phosphatidylcholine, diphosphatidylglycerol and phosphatidylglycerol, in addition to two unknown phospholipids. The major menaquinones in KS8 and KS9T were MK-10(H8), MK-11(H8), MK-10(H6) and MK-12. Furthermore, MK-13, MK-11(H6), MK-9(H8) and MK-10(H4) could be detected in significant amounts. The fatty acid composition included iso- and anteiso-branched acids combined with tuberculostearic acid (Me18:0), straight-chain saturated (16:0, 18:0) and unsaturated (16:1, 17:1, 18:1) fatty acids. On the basis of these results, KS8 and KS9T clearly represent a novel species of the genus Nocardiopsis, for which the name Nocardiopsis compostus sp. nov. is proposed (type strain KS9T = DSM 44551T= NRRL B-24145T). (+info)
Glasshouse behaviour of eight transgenic potato clones with a modified nitrate reductase expression under two fertilization regimes.
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In this study, eight transformed Solanum tuberosum L. plants, affected in their nitrate assimilatory pathway by the introduction of a tobacco nitrate reductase gene (Nia2), were cultivated in glasshouse conditions at INRA Ploudaniel (West Brittany, France). Two irrigation regimes were compared and plants were sampled at four stages of vegetation. Yield, tuber dry matter content, total nitrogen content, nitrate content in the whole plant, and nitrate reductase activities were studied. High frequency irrigation with nutritive solutions negatively affects both yield and dry matter content in tubers. Moreover, the introduction of the tobacco Nia2 gene in the potato genome does not seem to affect the agronomical parameters of the initial genotype apart from the nitrate content of tubers. Five transgenic genotypes out of eight, in fact, showed a drastic decrease (of around 98%) in their tuber nitrate content. This nitrate decrease in the tubers was also correlated with the presence of the mRNA transgene, whereas the potato nitrate reductase transcript does not seem to be expressed in wild-type tubers. Regarding these genotypes, developmental stage and nutritive solution supply were found to have no effect on tuber nitrate content. In fact, tubers derived from these clones exhibited low nitrate content throughout the vegetation period, while nitrate accumulation in wild-type tubers is progressive and increases sharply with high nutritive solution supply. (+info)
Identification of a cDNA from the arbuscular mycorrhizal fungus Glomus intraradices that is expressed during mycorrhizal symbiosis and up-regulated by N fertilization.
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A cDNA library was constructed with RNA from Glomus intraradices-colonized lettuce roots and used for differential screening. This allowed the identification of a cDNA (Gi-1) that was expressed only in mycorrhizal roots and was of fungal origin. The function of the gene product is unknown, because Gi-1 contained a complete open reading frame that was predicted to encode a protein of 157 amino acids which only showed little homology with glutamine synthetase from Helicobacter pylori. The time-course analysis of gene expression during the fungal life cycle showed that Gi-1 was expressed only during the mycorrhizal symbiosis and was not detected in dormant or germinating spores of G. intraradices. P fertilization did not significantly change the pattern of Gi-1 expression compared with that in the unfertilized treatment, whereas N fertilization (alone or in combination with P) considerably enhanced the Gi-1 transcript accumulation. This increase in gene expression correlated with plant N status and growth under such conditions. The possible role of the Gi-1 gene product in intermediary N metabolism of arbuscular mycorrhizal symbiosis is further discussed. (+info)
Soil fertility and biodiversity in organic farming.
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An understanding of agroecosystems is key to determining effective farming systems. Here we report results from a 21-year study of agronomic and ecological performance of biodynamic, bioorganic, and conventional farming systems in Central Europe. We found crop yields to be 20% lower in the organic systems, although input of fertilizer and energy was reduced by 34 to 53% and pesticide input by 97%. Enhanced soil fertility and higher biodiversity found in organic plots may render these systems less dependent on external inputs. (+info)
Interactions of pathogens and irritant chemicals in land-applied sewage sludges (biosolids).
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BACKGROUND: Fertilisation of land with processed sewage sludges, which often contain low levels of pathogens, endotoxins, and trace amounts of industrial and household chemicals, has become common practice in Western Europe, the US, and Canada. Local governments, however, are increasingly restricting or banning the practice in response to residents reporting adverse health effects. These self-reported illnesses have not been studied and methods for assessing exposures of residential communities to contaminants from processed sewage sludges need to be developed. METHODS: To describe and document adverse effects reported by residents, 48 individuals at ten sites in the US and Canada were questioned about their environmental exposures and symptoms. Information was obtained on five additional cases where an outbreak of staphylococcal infections occurred near a land application site in Robesonia, PA. Medical records were reviewed in cases involving hospitalisation or other medical treatment. Since most complaints were associated with airborne contaminants, an air dispersion model was used as a means for potentially ruling out exposure to sludge as the cause of adverse effects. RESULTS: Affected residents lived within approximately 1 km of land application sites and generally complained of irritation (e.g., skin rashes and burning of the eyes, throat, and lungs) after exposure to winds blowing from treated fields. A prevalence of Staphylococcus aureus infections of the skin and respiratory tract was found. Approximately 1 in 4 of 54 individuals were infected, including 2 mortalities (septicaemia, pneumonia). This result was consistent with the prevalence of S. aureus infections accompanying diaper rashes in which the organism, which is commonly found in the lower human colon, tends to invade irritated or inflamed tissue. CONCLUSIONS: When assessing public health risks from applying sewage sludges in residential areas, potential interactions of chemical contaminants with low levels of pathogens should be considered. An increased risk of infection may occur when allergic and non-allergic reactions to endotoxins and other chemical components irritate skin and mucus membranes and thereby compromise normal barriers to infection. (+info)
Dhurrin synthesis in sorghum is regulated at the transcriptional level and induced by nitrogen fertilization in older plants.
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The content of the cyanogenic glucoside dhurrin in sorghum (Sorghum bicolor L. Moench) varies depending on plant age and growth conditions. The cyanide potential is highest shortly after onset of germination. At this stage, nitrogen application has no effect on dhurrin content, whereas in older plants, nitrogen application induces an increase. At all stages, the content of dhurrin correlates well with the activity of the two biosynthetic enzymes, CYP79A1 and CYP71E1, and with the protein and mRNA level for the two enzymes. During development, the activity of CYP79A1 is lower than the activity of CYP71E1, suggesting that CYP79A1 catalyzes the rate-limiting step in dhurrin synthesis as has previously been shown using etiolated seedlings. The site of dhurrin synthesis shifts from leaves to stem during plant development. In combination, the results demonstrate that dhurrin content in sorghum is largely determined by transcriptional regulation of the biosynthetic enzymes CYP79A1 and CYP71E1. (+info)
The effects of abiotic factors on induced volatile emissions in corn plants.
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Many plants respond to herbivory by releasing a specific blend of volatiles that is attractive to natural enemies of the herbivores. In corn (Zea mays), this induced odor blend is mainly composed of terpenoids and indole. The induced signal varies with plant species and genotype, but little is known about the variation due to abiotic factors. Here, we tested the effect of soil humidity, air humidity, temperature, light, and fertilization rate on the emission of induced volatiles in young corn plants. Each factor was tested separately under constant conditions for the other factors. Plants released more when standing in dry soil than in wet soil, whereas for air humidity, the optimal release was found at around 60% relative humidity. Temperatures between 22 degrees C and 27 degrees C led to a higher emission than lower or higher temperatures. Light intensity had a dramatic effect. The emission of volatiles did not occur in the dark and increased steadily with an increase in the light intensity. An experiment with an unnatural light-dark cycle showed that the release was fully photophase dependent. Fertilization also had a strong positive effect; the emission of volatiles was minimal when plants were grown under low nutrition, even when results were corrected for plant biomass. Changes in all abiotic factors caused small but significant changes in the relative ratios among the different compounds (quality) in the induced odor blends, except for air humidity. Hence, climatic conditions and nutrient availability can be important factors in determining the intensity and variability in the release of induced plant volatiles. (+info)
The use of urban sewage sludge on pastures: the cysticercosis threat.
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Urban sewage production is increasing and its agronomical use as a fertiliser has been advocated. Considerable defiance is prevalent in consumers and among farmers on the use of such fertilisers due to unknown pathological or environmental risks. The aim of the present review was to consider which pathological risk is major. Cysticercosis due to Taenia saginata appears to be one of the major pathological threats when sewage sludge is used to fertilise cattle pastures in temperate areas. The situation is different in Africa (Taenia solium and T. saginata are both highly prevalent) and Asia (Taeniasaginata-like are prevalent). The processing of sludge and the delay between its application onto a pasture and grazing are probably major risk factors. Little data are available on the influence of processing, delay between processing and the use of sludge on the pathogenic risk. Producers and consumers will be more confident on the use of sludge if objective data are gained on risk. Most of the cases of cysticercosis (North America, United-Kingdom, Germany or Denmark) are related to poor human hygiene or accidental overflooding of sewage plants onto pastures. The standard application of sludge on pastures is apparently at low risk. This low risk does not mean that surveillance should cease since outbreaks of cysticercosis have been reported. Future investigations should concentrate on the most sustainable means of reducing risk (length of storage before use, composting, other treatments). (+info)