Cytochrome P-450 mediated genetic activity and cytotoxicity of seven halogenated aliphatic hydrocarbons in Saccharomyces cerevisiae

Cells of Saccharomyces cerevisiae, harvested from log-phase cultures, contain cytochrome P-450 and are capable of metabolizing promutagens to genetically active products. The activities of 7 halogenated aliphatic hydrocarbons in the yeast system have been investigated. All of the compounds tested (methylene chloride, halothane, chloroform, carbon tetrachloride, trichloroethylene, tetrachloroethylene and s-tetrachloroethane) induced mitotic gene convertants and recombinants and, to a lesser extent, gene revertants when incubated with logphase cells of the yeast strain D7. An examination of the difference spectra observed upon the addition of carbon tetrachloride, halothane and trichloroethylene to whole-cell or microsomal suspensions of yeast suggested that cytochrome P-450 mediated the metabolism of the hydrocarbons tested to cytotoxic and genetically active compounds.     

表面活性剂影响微生物降解多环芳烃的研究进展

多环芳烃(Polycyclic Aromatic Hydrocarbons,PAHs)的强疏水性是阻止其在土壤和水环境中微生物降解的主要因素.表面活性剂由于能够提高PAHs的表观溶解度而在PAHs的微生物降解中得到了广泛研究.截至目前,有关化学或生物表面活性剂促进PAHs的微生物降解已有大量报道,然而也有学者发现了表面...     

Detoxification spectrum of the cigarette beetle symbiont Symbiotaphrina kochii in culture

The ability of cultures of the cigarette beetle symbiont, Symbiotaphrina kochii Jurzitza ex. W. Gams and v. Arx, to utilize toxins as carbon sources and produce detoxifying enzymes was tested. This yeast could apparently use many of the plant allelochemicals, meal toxins, mycotoxins, insecticides, and herbicides tested as carbon sources, suggesting the ability to detoxify these compounds. Detoxifying enzymes that were detected using representative substrates included aromatic ester hydrolase, glucosidase, phosphatase, and glutathione transferase. This yeast was also able to hydrolyze the organophosphorus insecticide parathion. Thus, this yeast appears to have broad-spectrum detoxifying capabilities. Either this strain of yeast, improved strains, or other microorganisms to which genetic material from this yeast has been transferred may be of use in decontaminating materials containing multiple toxins.     

Local anesthetics, antipsychotic phenothiazines, and cationic surfactants shut down intracellular reactions through membrane perturbation in yeast

High osmolarity and glucose deprivation cause rapid shutdowns of both actin polarization and translation initiation in yeast. Like these stresses, administration of local anesthetics and of antipsychotic phenothiazines caused similar responses. All these drugs have amphiphilic structures and formed emulsions and permeabilized the cell membrane, indicating that they have the same features as a surfactant. Consistently with this, surfactants induced responses similar to those of local anesthetics and phenothiazines. Benzethonium chloride, a cationic surfactant, showed a more potent shutdown activity than phenothiazines, whereas SDS, an anionic surfactant, transiently depolarized actin without inhibiting translation initiation, suggesting that a cationic charge in the amphiphile is important to the shutdown of both reactions. The clinical drugs and the cationic surfactants at low concentrations caused shutdown without membrane permeabilization, suggesting that these compounds and stresses activate shutdown, via perturbation rather than disruption of the cell membrane.     

Exophiala macquariensis sp. nov., a cold adapted black yeast species recovered from a hydrocarbon contaminated sub-Antarctic soil

A new black yeast species, Exophiala macquariensis is described that is a member of the ascomycete family Herpotrichiellaceae, order Chaetothyriales. The genus Exophiala is comprised of opportunistic pathogens isolated from clinical specimens as well as species recovered from hydrocarbon contaminated environments. Several species have been reported to be able to degrade benzene, toluene, ethylbenzene and xylenes. Here, a novel species of Exophiala (CZ06) previously isolated from a Sub-Antarctic, Macquarie Island soil that was spiked with Special Antarctic Blend diesel fuel (SAB) is described. This isolate has the capacity of toluene biodegradation at cold temperatures. Multilocus sequence typing showed that this fungus was closely related to the pathogenic species Exophiala salmonis and Exophiala equina. With the capacity to utilise hydrocarbons as a sole carbon source at 10 °C, this fungus has great potential for future bioremediation applications.     

Expression of aldehyde dehydrogenase 6 reduces inhibitory effect of furan derivatives on cell growth and ethanol production in Saccharomyces cerevisiae

Yeast dehydrogenases and reductases were overexpressed in Saccharomyces cerevisiae D452-2 to detoxify 2-furaldehyde (furfural) and 5-hydroxymethyl furaldehyde (HMF), two potent toxic chemicals present in acid-hydrolyzed cellulosic biomass, and hence improve cell growth and ethanol production. Among those enzymes, aldehyde dehydrogenase 6 (ALD6) played the dual roles of direct oxidation of furan derivatives and supply of NADPH cofactor to their reduction reactions. Batch fermentation of S. cerevisiae D452-2/pH-ALD6 in the presence of 2 g/L furfural and 0.5 g/L HMF resulted in 20-30% increases in specific growth rate, ethanol concentration and ethanol productivity, compared with those of the wild type strain. It was proposed that overexpression of ALD6 could recover the yeast cell metabolism and hence increase ethanol production from lignocellulosic biomass containing furan-derived inhibitors.     

Relation between Candida maltosa Hydrophobicity and Hydrocarbon Biodegradation

Summary The growth of Candida maltosa on hydrocarbons (dodecane and hexadecane) was influenced by adding various natural and synthetic surfactants. Microbial adhesion to the hydrocarbon was used to measure the surface cell hydrophobicity of the yeast, which in the presence of a synthetic surfactant correlated with the degree of hydrocarbon biodegradation. Non-ionic surfactants caused the highest degree of hydrocarbon biodegradation corresponding the lowest hydrophobicity. A different correlation was observed with natural surfactants, of which saponin was the most effective for hydrocarbon biodegradation, though the concentration of this surfactant had no influence on surface cell hydrophobicity.     

Syntheses and structural studies of platinum(II) complexes of O-methylselenomethionine and related ligands

The complexes dichloro[2-(phenylselanyl)ethanamine]platinum(II), dichloro[2-(benzylselanyl)ethanamine]platinum(II) and dichloro(O-methylselenomethionine)platinum(II) have been prepared and the structure of dichloro(O-methylselenomethionine)platinum(II) has been determined by single crystal X-ray diffraction. The Pt(II) is in a square planar environment and is coordinated by two cis chloride ligands and a chelating O-methylselenomethionine ligand. The cytotoxicities of the compounds have been assessed in the human cell lines HeLa and K562 and they are at least threefold less toxic than cisplatin in both cell lines.     

Screening the essential oil composition of wild Sicilian fennel

Fifty-six samples of wild fennel (Foeniculum vulgare Mill.) have been collected in different localities of Sicily and analysed for their content in seed essential oils. The GC-FID-MS analyses allowed identifying 78 compounds, representing more than 98% of the oils. Phenylpropanoids are the most highly represented components – 55 samples show estragole as the main compound ranging between 34 and 89%, while (E)-anethole is the other phenylpropanoid ranging between 0.1 and 36%, although it only reaches appreciable values in a few samples, largely being present below 1%. The oxygenated monoterpene, fenchone, a typical fennel oil component, has been found in all samples, in the 2–27% range; α-pinene (1–21%), limonene (1–17%) and γ-terpinene (<1–4%) were the monoterpene hydrocarbons found in all samples. Only one sample showed piperitenone oxide and limonene as main components, with 42 and 34%, respectively, and with the lack of any phenylpropanoid. Sesquiterpenes and others compounds class had only negligible values or were not detected in all samples. Statistical analyses allowed to single out five groups, reflecting the compositional differences of the essential oil profiles of the wild Sicilian fennel.     

Functions of DEAD-box proteins in bacteria: Current knowledge and pending questions

DEAD-box proteins are RNA-dependent ATPases that are widespread in all three kingdoms of life. They are thought to rearrange the structures of RNA or ribonucleoprotein complexes but their exact mechanism of action is rarely known. Whereas in yeast most DEAD-box proteins are essential, no example of an essential bacterial DEAD-box protein has been reported so far; at most, their absence results in cold-sensitive growth. Moreover, whereas yeast DEAD-box proteins are implicated in virtually all reactions involving RNA, in E. coli (the bacterium where DEAD-box proteins have been mostly studied) their role is limited to ribosome biogenesis, mRNA degradation, and possibly translation initiation. Plausible reasons for these differences are discussed here.     

Structural heterogeneity of the plasmalemma of the yeast,Schwanniomyces occidentalis,induced by substrate

The growth of the yeast Schwanniomyces occidentalis on hydrocarbons (C₁₂?C₂₀) is followed by the formation of spherical invaginations. They are inwardly directed and border the ‘canals’ of the cell wall forming with them a single complex. The invaginations differ from the rest (smooth) part of the plasmalemma in the density of intramembrane particles. There is also a significant difference in the distribution of intramembrane particles in the plasmalemma of S. occidentalis grown on hydrocarbons and glucose. Invaginations and ‘canals’ are considered as a manifestation of the structural heterogeneity of the yeast cell envelope induced by a hydrocarbon substrate and, evidently, conditioned by adaptive processes.     

A vacuolar carboxypeptidase mutant of Arabidopsis thaliana is degraded by the ERAD pathway independently of its N-glycan

Misfolded proteins produced in the endoplasmic reticulum (ER) are degraded by a mechanism, the ER-associated degradation (ERAD). Here we report establishment of the experimental system to analyze the ERAD in plant cells. Carboxypeptidase Y (CPY) is a vacuolar enzyme and its mutant CPY∗ is degraded by the ERAD in yeast. Since Arabidopsis thaliana has AtCPY, an ortholog of yeast CPY, we constructed and expressed fusion proteins consisting of AtCPY and GFP and of AtCPY∗, which carries a mutation homologous to yeast CPY∗, and GFP in A. thaliana cells. While AtCPY-GFP was efficiently transported to the vacuole, AtCPY∗-GFP was retained in the ER to be degraded in proteasome- and Cdc48-dependent manners. We also found that AtCPY∗-GFP was degraded by the ERAD in yeast cells, but that its single N-glycan did not function as a degradation signal in yeast or plant cells. Therefore, AtCPY∗-GFP can be used as a marker protein to analyze the ERAD pathway, likely for nonglycosylated substrates, in plant cells.     

Influence of phytogenic surfactants (quillaya saponin and soya lecithin) on bio-elimination of phenanthrene and fluoranthene by three bacteria

The influence of two phytogenic surfactants on the elimination of polycyclic aromatic hydrocarbons (PAH) was studied in shaken-batch cultures of three soil bacteria under axenic conditions. At sufficiently high concentrations, quillaya saponin and soybean lecithin solubilized phenanthrene or fluoranthene efficiently. However, complete solubilization of the PAH by lecithin only doubled the maximal rate of elimination of the two PAH compounds by Pseudomonas 0259, strain MKm (Rhizomonas ?) and Mycobacterium EMI 2. By contrast, quillaya saponin did not improve PAH bioavailability, and in strain MKm it caused significant growth lags above 2.5 g/l. Simultaneously with the elimination of the PAH the bacteria utilized the surfactants as substrates for growth. Intermediate formation of PAH metabolites was noted. The results suggest that some phytogenic surfactants might improve PAH bioavailability in rhizospheres.     

Essential oil composition of Eryngium rosulatum P.W. Michael ined.: A new undescribed species from eastern Australia

The essential oil composition from the aerial parts of a new Eryngium species from Australia, Eryngium rosulatum P.W. Michael ined., has been analysed by GC and GC/MS. A total of 34 compounds have been identified representing around 80% of the total oil. The main constituents of the oil were found to be β-elemene (16.0%) and bicyclogermacrene (12.5%). Other representative compounds were identified as δ-elemene (7.0%) and (E)-caryophyllene (5.9%). The sesquiterpene fraction (75.0%) was predominant in the essential oil of this species, most of these were hydrocarbons (53.8%). This paper represents the first study on this new, undescribed Australian species and its chemical composition.     

Harnessing the catabolic versatility of Gordonia species for detoxifying pollutants

The genus Gordonia includes variedly pigmented aerobic, non-motile, non-sporulating Gram positive (sometimes variable) coccoid forms and rods. Different isolates display distinguishing physiological traits and biochemical properties that are significant in remediation applications. Strains inherently prevalent in soils, seawater, sediments and wastewaters can degrade hydrocarbons. Immobilized cells and microbial consortia containing Gordonia species have been used for in situ applications. Hydrocarbon uptake in this Actinomycete is mediated by attachment to large droplets or by pseudosolubilization of substrates. Hydrocarbons so internalized are degraded by relevant enzymes that are innately present in this microorganism. Wild-type and recombinant strains also mediate desulfurization of polyaromatic sulfur heterocyclic compounds. This organism is metabolically capable of bringing about detoxification of phthalate esters. Two species namely, Gordonia polyisoprenivorans and Gordonia westfalica mediate degradation of rubber and the metabolic pathways involved in the process have been well-understood. Some members are able to transform nitriles into commercially valuable products and others degrade the explosive hexahydro-1,3,5-trinitro-1,3,5-triazine. Cholesterol, pyridine derivatives, fuel oxygenates, thiodiglycol, bis-(3-pentafluorophenylpropyl)-sulfide and 6:2 fluorotelomersulfonate are also biotransformed or degraded by Gordonia species. Some members of this genus are significant in the treatment of wastewaters including those that are rich in steroids and lignin. There are also several patents highlighting the commercial relevance of this genus. On account of its diverse catabolic properties, this Actinomycete has become important in bioremediation of polluted environments.     

Saccharomycopsis fibuligera and its applications in biotechnology

Saccharomycopsis fibuligera is found to actively accumulate trehalose from starch and the gene responsible for biosynthesis of trehalose has been cloned and its expression has been characterized. This yeast is also found to secrete a large amount of amylases, acid protease and β-glucosidase which have highly potential applications in fermentation industry. The genes encoding amylases, acid protease and β-glucosidase in S. fibuligera have been cloned and characterized. It is also used to produce ethanol from starch, especially cassava starch by co-cultures of Saccharomyces cereviase or Zymomonas mobilis.     

Entomopathogenic Nematode Production and Application Technology

Production and application technology is critical for the success of entomopathogenic nematodes (EPNs) in biological control. Production approaches include in vivo, and in vitro methods (solid or liquid fermentation). For laboratory use and small scale field experiments, in vivo production of EPNs appears to be the appropriate method. In vivo production is also appropriate for niche markets and small growers where a lack of capital, scientific expertise or infrastructure cannot justify large investments into in vitro culture technology. In vitro technology is used when large scale production is needed at reasonable quality and cost. Infective juveniles of entomopathogenic nematodes are usually applied using various spray equipment and standard irrigation systems. Enhanced efficacy in EPN applications can be facilitated through improved delivery mechanisms (e.g., cadaver application) or optimization of spray equipment. Substantial progress has been made in recent years in developing EPN formulations, particularly for above ground applications, e.g., mixing EPNs with surfactants or polymers or with sprayable gels. Bait formulations and insect host cadavers can enhance EPN persistence and reduce the quantity of nematodes required per unit area. This review provides a summary and analysis of factors that affect production and application of EPNs and offers insights for their future in biological insect suppression.     

Micellar and Biochemical Properties of (Hemi)Fluorinated Surfactants Are Controlled by the Size of the Polar Head

Surfactants with fluorinated and hemifluorinated alkyl chains have yielded encouraging results in terms of membrane protein stability; however, the molecules used hitherto have either been chemically heterogeneous or formed heterogeneous micelles. A new series of surfactants whose polar head size is modulated by the presence of one, two, or three glucose moieties has been synthesized. Analytical ultracentrifugation and small-angle neutron scattering show that fluorinated surfactants whose polar head bears a single glucosyl group form very large cylindrical micelles, whereas those with two or three glucose moieties form small, homogeneous, globular micelles. We studied the homogeneity and stability of the complexes formed between membrane proteins and these surfactants by using bacteriorhodopsin and cytochrome b₆f as models. Homogeneous complexes were obtained only with surfactants that form homogeneous micelles. Surfactants bearing one or two glucose moieties were found to be stabilizing, whereas those with three moieties were destabilizing. Fluorinated and hemifluorinated surfactants with a two-glucose polar head thus appear to be very promising molecules for biochemical applications and structural studies. They were successfully used for cell-free synthesis of the ion channel MscL.     

Biodegradation of xenobiotics by anaerobic bacteria

Xenobiotic biodegradation under anaerobic conditions such as in groundwater, sediment, landfill, sludge digesters and bioreactors has gained increasing attention over the last two decades. This review gives a broad overview of our current understanding of and recent advances in anaerobic biodegradation of five selected groups of xenobiotic compounds (petroleum hydrocarbons and fuel additives, nitroaromatic compounds and explosives, chlorinated aliphatic and aromatic compounds, pesticides, and surfactants). Significant advances have been made toward the isolation of bacterial cultures, elucidation of biochemical mechanisms, and laboratory and field scale applications for xenobiotic removal. For certain highly chlorinated hydrocarbons (e.g., tetrachlorethylene), anaerobic processes cannot be easily substituted with current aerobic processes. For petroleum hydrocarbons, although aerobic processes are generally used, anaerobic biodegradation is significant under certain circumstances (e.g., O₂-depleted aquifers, oil spilled in marshes). For persistent compounds including polychlorinated biphenyls, dioxins, and DDT, anaerobic processes are slow for remedial application, but can be a significant long-term avenue for natural attenuation. In some cases, a sequential anaerobic-aerobic strategy is needed for total destruction of xenobiotic compounds. Several points for future research are also presented in this review.