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PubMedDate not supplied

The production of extracellular mucilaginous material (ECMM) in two wood-rotting basidiomycetes is affected by growth conditions.

The ability of two wood-decay basidiomycetes to produce extracellular mucilaginous material (ECMM) and its relationship with total biomass production has been investigated. Growth and ECMM production by the white-rot fungus Coriolus versicolor and the brown-rot fungus Gloeophyllum trabeum were assessed in liquid culture under different nutritional and environmental conditions. Nutritional, pH and temperature factors all influenced significantly the proportion of ECMM in the total biomass produced. When total biomass production was reduced due to unfavorable growth conditions (stress), the proportion of ECMM in the biomass was elevated. The results are discussed with regard to the possible role(s) of ECMM in the responses of these fungi to stress.

Basidiomycota↗

PubMed2003

Overview of phytotechnologies.

Phytotechnologies are defined as: "The use of vegetation to contain, sequester, remove, or degrade inorganic and organic contaminants in soils, sediments, surface waters, and groundwater." This chapter is designed to provide the reader with a broad, introductory overview of phytotechnologies as well as environmental remediation in general. To familiarize the reader with the common acronyms, abbreviations, and parameters used in the environmental arena, an extensive list is provided for quick reference. Furthermore, due to the multi-disciplinary nature of phytotechnologies, a brief background on the pertinent information in plant physiology, soil microbiology, hydrogeology, and environmental engineering is provided as well. This covers the basic physiological processes occurring in the rhizosphere as well as in the plant system. Furthermore, these basic processes are related to the phytotechnology mechanisms that form the basis for the various applications used in the field today. Finally, basic design equations, site-specific considerations, and practical field implementation techniques are provided as well for the different applications.

Agriculture↗

PubMed1976

Chemistry, biological activity, and uses of formamidine pesticides.

The formamidines, a relatively new group of acaricide-insecticides, are novel both in their range of biological activities and in their mode of action, which is presently unknown. This paper is a review of the historical development, properties, structures, uses, and chemistry of this group of pesticides, with particular emphasis on chlordimeform (Galecron or Fundal), N'-4-chloro-o-tolyl-N,N-dimethylformamidine, and amitraz, 1,3=di-(2,4-dimethylphenylimino)-2-methyl-2-azapropane. Their biological activity and uses are defined by their toxicity to spider mites, ticks, and certain insects, and they are particularly effective against juvenile and resistant forms of these organisms. A significant, but poorly understood feature of their field effectiveness is their breadth of toxic action which includes direct lethality, excitant-repellant behavioral effects, and chemosterilization. They are generally of low hazard for nontarget species with the significant exception of predaceous mites. Several aspects of the chemistry of these compounds are considered, including structure--activity relations, synthetic pathways, isomerism and configuration, and their chemical and environmental stability. A significant feature of the metabolism and toxicity of these agents is the possible activation of chlordimeform by N-demethylation in vivo. Strong evidence for this has been presented with the cattle tick, but recent results discussed here suggest that in other species, i.e., mice, German cockroaches or black cutworm eggs, N-demethylation is neither a strong activation nor a detoxication reaction.

Amidines↗

PubMed2006

Modeling the impact of direct phototransformation on predicted environmental concentrations (PECs) of propranolol hydrochloride in UK and US rivers.

There is currently uncertainty on the persistence of active pharmaceutical ingredients (APIs) and on their depletion mechanisms in natural surface waters such as rivers, and hence predictions of their fate are often poor. In this study, a beta-adrenergic receptor, propranolol hydrochloride, was selected as a model API to explore the relative significance of direct phototransformation as a potential removal process of hydrophilic APIs in rivers. Phototransformation kinetics of propranolol was measured under simulated solar irradiation in the laboratory, which were then converted to the kinetics applicable in UK and US rivers. The effects of light intensity, light penetration, river size and flow were examined. The extrapolated phototransformation half-lives were applied in the river catchment models of GREAT-ER and PhATE. Results demonstrated that direct phototransformation significantly reduced the predicted environmental concentrations of propranolol in the water phase. Predicted reductions of mean concentrations in the River Aire (UK) were 27% in summer and 3% in winter; and for the US rivers simulated, reductions were 28-68% in summer and 11-41% in winter. The highest reductions were predicted for long rivers with low turbidity and low flow conditions.

Biodegradation, Environmental↗

PubMed1994

Biotransformations catalyzed by the genus Rhodococcus.

Rhodococci display a diverse range of metabolic capabilities and they are a ubiquitous feature of many environments. They are able to degrade short-chain, long-chain, and halogenated hydrocarbons, and numerous aromatic compounds, including halogenated and other substituted aromatics, heteroaromatics, hydroaromatics, and polycyclic aromatic hydrocarbons. They possess a wide variety of pathways for degrading and modifying aromatic compounds, including dioxygenase and monooxygenase ring attack, and cleavage of catechol by both ortho- and meta-routes, and some strains possess a modified 3-oxoadipate pathway. Biotransformations catalyzed by rhodococci include steroid modification, enantioselective synthesis, and the transformation of nitriles to amides and acids. Tolerance of rhodococci to starvation, their frequent lack of catabolite repression, and their environmental persistence make them excellent candidates for bioremediation treatments. Some strains can produce poly(3-hydroxyalkanoate)s, others can accumulate cesium, and still others are the source of useful enzymes such as phenylalanine dehydrogenase and endoglycosidases. Other actual or potential applications of rhodococci include desulfurization of coal, bioleaching, use of their surfactants in enhancement of oil recovery and as industrial dispersants, and the construction of biosensors.

Biodegradation, Environmental↗

PubMed1990

[The breakdown of phthalic acid esters by microorganisms].

The distribution in environment of phthalic acid esters classified according to their inherent toxicity, teratogenic, mutagenic properties and cancerogenic activity into a group of priority pollutants of biosphere is described in this review. The role of microbial community in degradation of phthalate esters has been demonstrated. The effect of such environmental factors as pH of the medium, temperature, humidity, concentration of organic matter, the introduction of promising microbial strains in natural biocenoses has been examined. The pathways of phthalate ester metabolism have been analysed in representatives of active bacterial destructors belonging to genera Nocardia, Pseudomonas and Micrococcus. The decomposition rate of phthalate esters has been shown to be correlated with structure, concentration and culture conditions.

Bacteria↗

PubMed2000

Engineering dioxygenases for efficient degradation of environmental pollutants.

Dioxygenases have recently been engineered to improve their capabilities for environmental pollutant degradation. The techniques used to achieve this include in vitro DNA shuffling and subunit or domain exchanges between dioxygenases of different bacterial origins. Such evolved enzymes acquire novel and enhanced degradation capabilities of xenobiotic compounds, such as polychlorinated biphenyls, trichloroethylene and a variety of aromatic compounds. Hybrid strains in which the evolved genes are integrated into the chromosomal operons exhibit efficient degradation of xenobiotic chlorinated compounds.

Amino Acid Sequence↗

PubMed2004

Occurrence and phylogenetic diversity of Sphingomonas strains in soils contaminated with polycyclic aromatic hydrocarbons.

Bacterial strains of the genus Sphingomonas are often isolated from contaminated soils for their ability to use polycyclic aromatic hydrocarbons (PAH) as the sole source of carbon and energy. The direct detection of Sphingomonas strains in contaminated soils, either indigenous or inoculated, is, as such, of interest for bioremediation purposes. In this study, a culture-independent PCR-based detection method using specific primers targeting the Sphingomonas 16S rRNA gene combined with denaturing gradient gel electrophoresis (DGGE) was developed to assess Sphingomonas diversity in PAH-contaminated soils. PCR using the new primer pair on a set of template DNAs of different bacterial genera showed that the method was selective for bacteria belonging to the family Sphingomonadaceae.Single-band DGGE profiles were obtained for most Sphingomonas strains tested. Strains belonging to the same species had identical DGGE fingerprints, and in most cases, these fingerprints were typical for one species. Inoculated strains could be detected at a cell concentration of 10(4) CFU g of soil(-1). The analysis of Sphingomonas population structures of several PAH-contaminated soils by the new PCR-DGGE method revealed that soils containing the highest phenanthrene concentrations showed the lowest Sphingomonas diversity. Sequence analysis of cloned PCR products amplified from soil DNA revealed new 16S rRNA gene Sphingomonas sequences significantly different from sequences from known cultivated isolates (i.e., sequences from environmental clones grouped phylogenetically with other environmental clone sequences available on the web and that possibly originated from several potential new species). In conclusion, the newly designed Sphingomonas-specific PCR-DGGE detection technique successfully analyzed the Sphingomonas communities from polluted soils at the species level and revealed different Sphingomonas members not previously detected by culture-dependent detection techniques.

Base Sequence↗

PubMed1986

Ecotoxicological profile of xylenes. Working Party on Ecotoxicological Profiles of Chemicals.

The xylenes (o, m, p), which are produced in large amounts and widely used, must be considered as environmental contaminants, as they have been identified in the atmosphere of many countries. Their acute and chronic toxicity in mammals is moderate. Mutagenic and teratogenic properties can be excluded. Carcinogenic potential has been at present inadequately studied. In man some disturbances are evident at the concentration of 45 ppm. Hepatic metabolism is a valid process of detoxification and its high rate limits the risk of accumulation of the xylenes in adipose tissue. Ecotoxicological data refer almost exclusively to water. No long-term tests have been made. However, the high volatility, elevated elimination, and the low factor of accumulation suggest the impact on aquatic environment should be limited. Xylenes are easily biodegraded by many microorganisms. Photoxydation is one of the main degradation processes, responsible for the disappearance of the xylenes from the atmosphere.

Animals↗

PubMed2003

Soil contamination and plant uptake of heavy metals at polluted sites in China.

We investigated heavy metal contamination in soils and plants at polluted sites in China including some with heavy industries, metal mining, smelting and untreated wastewater irrigation areas. We report our main findings in this paper. The concentrations of heavy metals, including Cd and Zn, in the soils at the investigated sites were above the background levels, and generally exceeded the Government guidelines for metals in soil. The concentrations of metals in plants served to indicate the metal contamination status of the site, and also revealed the abilities of various plant species to take up and accumulate the metals from the soil. Substantial differences in the accumulation of heavy metals were observed among the plant species investigated. Polygonum hydropiper growing on contaminated soils in a sewage pond had accumulated 1061 mg kg(-1) of Zn in its shoots. Rumex acetosa L. growing near a smelter had accumulated more than 900 mg kg(-1) of Zn both in its shoots and roots. Therefore these species have potential for phytoremediation of metal-contaminated sites. Our results indicate the need to elucidate the dynamics of soil metal contamination of plants and the onward movement of metal contaminants into the food chain. Also our results indicate that the consumption of rice grown in paddy soils contaminated with Cd, Cr or Zn may pose a serious risk to human health, because from 24 to 22% of the total metal content in the rice biomass was concentrated in the rice grain. Platanus acerifolia growing on heavily contaminated soil accumulated only very low levels of heavy metals, and this mechanism for excluding metal uptake may have value in crop improvement. Sources of metal entering the environmental matrices studied included untreated wastewater, tailings or slurries and dust depositions from metal ore mining, and sewage sludge. Pb, Zn or Cd concentrations declined with the distance from metal smelter in accordance with a good exponential correlation (R2>0.9), and this shows that metal dust deposition is an important contributor to metal contamination of soils.

Biodegradation, Environmental↗

PubMed1996

Use of monoclonal antibodies against dibenzo-p-dioxin degrading Sphingomonas sp. strain RW1.

A monoclonal antibody prepared against surface antigen of Sphingomonas sp. strain RW1 was used for the direct detection of RW1-like organisms in environmental samples by epifluorescence microscopy and subsequent confirmation by Western blot. Of the 76 samples collected from various sources and probed using epifluorescence, only one sample, effluent from paper and pulp processing, gave a positive result. The effluent was cultured and yielded an organism which, by Western blot analysis, was shown to contain the 28 kDa protein recognized by the monoclonal antibody.

Animals↗

PubMed2006

Oxygenases and dehalogenases: molecular approaches to efficient degradation of chlorinated environmental pollutants.

Microbial oxygenases and dehalogenases are key enzymes in the degradation of highly chlorinated compounds, which often become significant environmental pollutants. Oxygenases engineered by the methods of directed evolution exhibit enhanced degradation of PCBs and other chlorinated solvents such as trichloroethene and pentachloroethane. Dehalorespiration is an efficient dechlorination mechanism that is coupled with energy-yielding phosphorylation. Recently, a variety of chloroethene-dehalorespiring anaerobes have been isolated, and their reductive dehalogenases have been characterized in biochemical and genetic bases. This review describes our recent studies on dioxygenases and reductive dehalogenases.

Biodegradation, Environmental↗

PubMed2001

Methanol conversion in high-rate anaerobic reactors.

An overview on methanol conversion in high-rate anaerobic reactors is presented, with the focus on technological as well as microbiological aspects. The simple C1-compound methanol can be degraded anaerobically in a complex way, in which methanogens, sulfate reducing bacteria and homoacetogens interact cooperatively or competitively at substrate level. This interaction has large technological implications as it determines the final product of methanol mineralization, methane or carbon dioxide. The degradation route of methanol may be entirely different when environmental conditions change. Direct methanogenesis from methanol seems the predominant mineralization route under mesophilic conditions both in the absence and the presence of sulfate. Under thermophilic conditions methanol oxidation to carbon dioxide and hydrogen appears to play an important role. The UASB technology for mesophilic digestion of methanolic waste has presently reached full-scale maturity. The potential of methanol as feedstock for anaerobic processes is discussed.

Bacteria, Anaerobic↗

PubMed2002

Prospects and limitations of phytoremediation for the removal of persistent pesticides in the environment.

The environmental problems that have arisen from the use of persistent pesticides in the past, and potential sources of further contamination have been discussed. The potential and limitations of phytoremediation for removal of pesticides in the environment have been reviewed. The enzymatic processes in plants that are known to be involved in phytodegradation of pesticides, and possibilities for enhancing them have also been discussed.

Biodegradation, Environmental↗

PubMed2001

BMRI-2, Rossendorf/Dresden, Germany (30 August - 1 September 2000).

Clearly, there is much left to be understood about microbial processes and interactions with metals, but much progress has been made, and the multidisciplinary approach of groups who are studying both the microbial populations and the chemistry of biotransformations of metals by bacteria will ensure rapid progress in our understanding of these issues. Several major points from different speakers summarize this meeting and are usefully reiterated at this point: Toxic metal ions, unlike organic pollutants, are immutable, and their bioavailability is a critical feature of their toxicity. The mobility, transport and fate of toxic metals and radionuclides in the environment are dependent on chemical and geochemical processes in which micro-organisms are intimately involved. Metals can be mobilized as well as immobilized by microorganisms. Metal/radionuclide valencies and chemical properties are critical to their environmental mobility. Bacterial- or fungal-metal interactions will be complicated by the presence of other pollutants. The identification of bacteria from environmental samples should not rely on one methodology, as these have been shown to be biased. Sonja Selenska-Pobell organized both BMRI-1 in 1998 and BMRI-2, which had well over 100 participants from Europe, Russia, USA and Japan in attendance. Thirty-one oral presentations were given, and over 30 posters were displayed over two poster sessions. BMRI-3 is provisionally planned for 2002 at GBF, Braunschweig, Germany.

Bacteria↗

PubMedDate not supplied

Scanning force microscopy studies of the colonization and growth of A. ferrooxidans on the surface of pyrite minerals.

We have used the technique of scanning force microscopy (SFM) for studying the interaction of the bacteria A. ferrooxidans with the surface of the mineral pyrite. These bacteria are important to study with regard to acidification of streams and the environmental impact of such acidification. A. ferrooxidans cells readily colonize the pyrite surface, forming a tight mineral seal between the cell and the pyrite substrate. These bacteria subsequently may grow under pH neutral conditions, biooxidizing the underlying pyrite; this process creates etch pits in the pyrite. On average, these etch pits are 1.2 microns in lateral dimension and approximately 220 nm deep.

Acidithiobacillus↗

PubMed1996

Environmental processes mediated by iron-reducing bacteria.

Considerable progress has been made towards enhancing our understanding of the phylogeny, ecology and biogeochemical role of dissimilatory iron-reducing bacteria. The known phylogenetic range of iron-reducing bacteria has expanded considerably, as has the known range of iron minerals that serve as a source of Fe(III) for anaerobic respiration. In addition, the number of biotechnological applications of iron-reducing bacteria, including remediation of soils and sediments contaminated with metals, radionuclides and organics, is rapidly expanding.

Bacteria↗

PubMedDate not supplied

Phytoremediation of selenium-contaminated soils and waters: fundamentals and future prospects.

Interest in selenium pollution and remediation technology has escalated during the past two decades. Although not known to be essential for plants, selenium is an essential micronutrient for humans and animals, having important benefits for their nutrition. At high concentrations, however, selenium becomes toxic to animals and humans. A major selenium controversy in the 1980s emerged in California at the Kesterson National Wildlife Refuge; hence, scientists, environmental regulators, politicians, and the general public in the United States became aware of selenium's potential as an environmental contaminant. Consequently, extensive research has been conducted in the western United States, and a vast amount of financial resources have been allocated to develop management strategies and remediation technologies for reducing the impact of naturally occurring selenium on the biological environment. A plant-based technology, defined as 'phytoremediation', has received increasing recognition as a low-cost, environmentally friendly approach for managing the toxic effects of selenium. Plants have the ability to absorb and sequester selenium and to convert inorganic selenium to volatile forms of organic compounds that are released harmlessly into the atmosphere. The present review summarizes recent research findings and information about strategies on using phytoremediation systems to detoxify selenium-contaminated soils and waters in natural and agricultural ecosystems.

Antioxidants↗