Yeast sequencing reports. Isolation and sequence analysis of a gene from the linear DNA plasmid pPAC1–2 of Pichia acaciae that shows similarity to a killer toxin gene of Kluyveromyces lactis

The toxin-encoding linear plasmid systems found in Pichia acaciae and Kluyveromyces lactis yeasts appear to be quite similar, both in function and structural organization. By Southern hybridization, a linear plasmid of P. acaciae, pPac1–2, was found to hybridize to the second open reading frame (ORF2) of K. lactis plasmid pGKL1, known to encode the α and β subunits of the K. lactis toxin. A 1·7 kbp segment of pPac1–2 DNA was cloned, sequenced and shown to contain four regions of strong homology to four similarly oriented regions of K. lactis ORF2. This 1·7 kbp fragment also contained an ORF of 1473 bp that could encode a protein of ～ 55·8 kDa. Like the α subunit gene of K. lactis ORF2, a very hydrophobic region occurs at the N-terminus, perhaps representing a signal sequence for transport out of the cell. Unlike K. lactis ORF2, however, the encoded polypeptide is much smaller and lacks a recognizable domain common to chitinases. The structure of a toxin that includes the translation product of this P. acaciae ORF would likely be quite different from that of the K. lactis toxin. Analysis of the upstream region of the P. acaciae ORF revealed an upstream conserved sequence identical to that found before ORFs 8 and 9 of pGKL2. A possible hairpin loop structure, as has been described for each of the four K. lactis pGKL1 ORFs, was found just upstream of the presumed start codon. The similarity of the promoter-like elements found in the linear plasmid genes of these diverse yeasts reinforces the idea of the existence of a unique, but highly conserved, expression system for these novel plasmids. The sequence has been deposited in the GenBank data library under Accession Number U02596.     

胨冻样芽孢杆菌(Bacillus mucilaginosus)对烟草灰霉病菌(Botrytis cinerea)的抑制作用

本文首次报道胨冻样芽孢杆菌XDB1和D4B1对烟草灰霉病菌(Botrytis cinerea)的抑制作用。实验表明,XDB1和D4B1的发酵原液和无细胞提取物具有相同的抑菌效果,而经121℃处理30分钟后,抑菌活性丧失。D481菌株的抑菌活性高于XDB1,钾长石作为基质时的活性高于土壤矿物。但是,XDB1和D481对立枯丝核病菌(R..solani)、西瓜尖孢镰刀菌(F.oxysporum)、腐霉(Pythium sp)、小麦全蚀病菌(G.graminis)、烟炭疽病菌(C.gloeosporides)、烟草赤星病菌(A.alternata)、烟草黑胫病菌(P.nicotianae、串珠镰刀病菌(F.moniliforme)和水稻稻瘟病菌(P.grisea)无抑制作用。     

Fire performance of wood (Pinus radiata) treated with fire retardants and a wood preservative

In this work, we co‐formulated an oil‐borne copper naphthenate/permethrin wood preservative system with synthetic polymer‐based fire‐retardant additives prior to the impregnation of Pinus radiata sapwood. We evaluated what effect, if any, the preservative had upon the fire performance properties of the fire retardants and whether the fire retardants impacted on the fungicidal and termiticidal efficacy of the preservative. The fire retardants included halogenated and phosphorus‐based systems. A mass loss calorimeter, in conjunction with a thermopile, was used to measure the time to ignition and the peak heat release rate (PHRR) from which the fire performance index (FPI) was determined. The preservative properties were evaluated using termite and soil‐block decay bioassays. In summary, we found that the rate of fire growth was reduced when the fire retardants were used in combination with the wood preservative. We also found that the PHRR was a better determinant of fire performance than the FPI. The performance of the wood preservative was enhanced against fungal decay and termite attack when used in combination with the fire retardants. The fire retardants also demonstrated some wood preservative properties of their own. Copyright © 2008 John Wiley & Sons, Ltd.     

海洋丝状真菌转化石油烃的研究

研究从湄洲湾海域分离的4株丝状真菌MF1，MF2，MF3，MF4的生长特性及去除油污的过程，观察在温度26℃，初始油浓度在3g/l,培养12d的过程中培养液的变化，分析培养液的pH值及原油的去除率与时间的关系，结果表明，丝状真菌去除原油的[过程是生物吸附与生物降解相结合的生物转化过程，比较革兰氏阴性细菌与丝状真菌细胞壁组成，结构，得出海洋微生物的脱油作用与其细胞壁有直接的关系。     

丝状真菌纤维素酶合成机制的研究

丝状真菌产生的纤维素酶被认为是最有应用前景的,但就目前酶生产效率来看,离实际应用还有很大的差距,需要对酶的合成调节机制有更为全面和深刻的了解。纤维素酶的生物合成受诱导和阻遏双重控制,酶的生产既有赖于低廉的保持一定浓度诱导物的存在,又必须清除分解代谢产物对酶合成的阻遏,其中的详细机制有待进一步的阐明。真菌纤维素酶的分泌也是相当复杂的,在酶的分泌过程中,酶会发生例如糖基化等一系列变化。提高纤维素酶的活力测定方法的准确性,使其进一步规范化,是研究纤维素酶工作的另外一个重要的领域。随着现代生物学朝着分子水平的不断发展,分子生物学的许多方法也越来越多地被应用于纤维素酶的研究中,并取得了重要进展。对真菌纤维素酶合成调节机制的深入研究,将为提高纤维素酶产量,推动应用工作的发展打下理论基础。     

Bioremediation of polycyclic aromatic hydrocarbons: current knowledge and future directions

Polycyclic aromatic hydrocarbons (PAHs) are a class of organic compounds that have accumulated in the natural environment mainly as a result of anthropogenic activities such as the combustion of fossil fuels. Interest has surrounded the occurrence and distribution of PAHs for many decades due to their potentially harmful effects to human health. This concern has prompted researchers to address ways to detoxify/remove these organic compounds from the natural environment. Bioremediation is one approach that has been used to remediate contaminated land and waters, and promotes the natural attenuation of the contaminants using the in situ microbial community of the site. This review discusses the variety of fungi and bacteria that are capable of these transformations, describes the major aerobic and anaerobic breakdown pathways, and highlights some of the bioremediation technologies that are currently available. Copyright © 2005 Society of Chemical Industry     

Influence of oleoresin constituents fromPinus ponderosa andPinus jeffreyi on growth of mycangial fungi fromDendroctonus ponderosae andDendroctonus jeffreyi

Dendroctonus jeffreyi andD. ponderosae are morphologically similar sympatric species of pine bark beetles over portions of their geographic ranges; however,D. jeffreyi is monophagous onP. jeffreyi whileD. ponderosae is highly polyphagous. Both species carry a species of mycangial fungi that are also very similar in appearance. Growth of the two mycangial fungi and of the fungusLeptographium terebrantis (associated with the polyphagous and non-tree-killingDendroctonus valens) in the presence of oleoresin constituents of host and nonhost conifers was tested by placing individual chemicals on agar growth medium and by growing the cultures in saturated atmospheres of the chemicals. The fungus associated withD. jeffreyi showed greater tolerance for chemical constituents placed on the growth medium than the other two fungi, and growth after three days was enhanced by heptane, the dominant constituent ofP. jeffreyi oleoresin. Growth of all three species of fungi was reduced by the resin constituents when the chemicals were presented as saturated atmospheres. The results suggest that the influence of the tree on growth of the symbiotic fungi of the bark beetles during the initial attack process may be different than after colonization by the beetles is complete. The difference in the responses of the apparently related species of mycangial fungi may provide some new insight into the evolutionary history of these beetle/mycangial fungus/host tree systems.     

Flavonoids released by carrot (Daucus carota) seedlings stimulate hyphal development of vesicular-arbuscular mycorrhizal fungi in the presence of optimal CO2 enrichment

Carbon dioxide has been previously identified as a critical volatile factor that stimulates hyphal growth ofGigaspora margarita, a vesiculararbuscular mycorrhizal fungus, and we determined the optimal concentration at 2.0%. The beneficial effect of CO₂ on fungal development is also visible in the presence of stimulatory (quercetin, myricetin) or inhibitory (naringenin) flavonoids. Sterile root exudates from carrot seedlings stimulate the hyphal development ofG. margarita in the presence of optimal CO₂ enrichment. Three flavonols (quercetin, kaempferol, rutin or quercetin 3-rutinoside) and two flavones (apigenin, luteolin) were identified in carrot root exudates by means of HPLC retention time. Flavonols like quercetin and kaempferol are known to have stimulatory effects on hyphal growth ofG. margarita.     

浸铀真菌的分离和纯化研究

为获得浸铀真菌纯种,应用Dox（-）培养基、沙堡培养基（SDA培养基）、PDA培养基、Dox（＋）培养基进行了铀矿石中真菌的分离,挑取孢子进行了纯化培养,共获得具有产酸能力的真菌4株,其中黑曲霉1株,青霉3株.试验结果表明,铀矿石中存在大量真菌,部分真菌具有产酸能力,并且这些产酸真菌生长速度较快,具有浸铀的潜力.     

Influence of Phenolic acids on microbial populations in the rhizosphere of cucumber

Experiments were conducted to determine whether changes in soil microbial populations that occur in response to additions of certain allelopathic phenolic acids to bulk soil also occur in the rhizosphere. Cucumber seedlings were transplanted into cups containing a nutrient-enriched mixture of Portsmouth B₁, soil and sand and were watered five times (once every 48 hr) with aqueous solutions of ferulic,p-coumaric, or vanillic acid (each at 0, 0.25, or 0.50ol/g soil material). Nutrient solution was applied on alternate days. Leaf growth was suppressed by up to 42% by phenolic acids, but changes in root growth varied with the compound and concentration in solution. Significant increases (over 600% relative to controls) in populations of fast-growing bacteria in the rhizosphere were detected after two but not after five treatments, and increases (400% relative to controls) in numbers of fungal propagules were detected after five treatments. Such increases suggested that chronic exposure to a phenolic acid might resuit in high populations of rhizosphere microorganisms that could metabolize the compounds and thus alter observable responses by the plant. To test this, plants were watered repeatedly with a low-concentration solution of ferulic acid (chronic treatments; 0.0 or 0.1mol/g soil material in one experiment, 0.000 or 0.025imol/g soil material in a second) and then once with a highconcentration solution (acute treatment; 0.0, 0.5, or 1.0mol/g soil material in the first experiment; 0.000, 0.125, or 0.250mol/g soil material in the second).Paper No. 12385 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, North Carolina. The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service or the United States Department of Agriculture of the products named, nor criticism of similar ones not mentioned. Acute treatments and some chronic treatments suppressed leaf growth, but results were inconsistent for root growth. Acute treatments increased numbers of several types of bacteria in the rhizosphere but had inconsistent effects on fungi. Chronic treatments had no effect on numbers of bacteria or fungal propagules in the rhizosphere. Furthermore, chronic treatments did not alter responses of plants or microbial populations to the subsequent acute treatment. Results demonstrated that phenolic acids in soil, which must pass through the rhizosphere before interaction with plant roots can occur, alter the microbial ecology of the rhizosphere. However, microbially mediated acclimation of plants to relatively high concentrations of ferulic acid was not observed.