Interactions between Glomus mosseae and arbuscular mycorrhizal sporocarp-associated saprophytic fungi

The saprophytic fungi Wardomyces inflatus (Marchal) Hennebert, Paecilomyces farinosus (Holm & Gray) A. H. S. Brown & G. Sm., Gliocladium roseum Bain., sterile dark mycelium (SDM-54), Trichoderma pseudokoningii Rifai and Trichoderma harzianum Rifai were isolated from sporocarps of Glomus mosseae. The effect of saprophytic fungi on G. mosseae spore germination was tested on water agar. Wardomyces inflatus decreased the percent germination of G. mosseae spores; G. roseum, T. pseudokoningii and T. harzianum had no effect on germination; and P. farinosus and SDM-54 increased the percentage of spore germination of G. mosseae after 4 d. Wardomyces inflatus significantly decreased hyphal length of spores which germinated, but no other saprophytic fungi affected hyphal growth. Trichoderma pseudokoningii, T. harzianum, P. farinosus and SDM-54 increased the number of auxiliary cells formed by G. mosseae. The effect of saprophytic fungi on arbuscular mycorrhizal colonization of soybean was studied in a greenhouse trial. The percentage of soybean root length colonized was decreased by W. inflatus, unaffected by SDM-54 and T. harzianum, and increased by P. farinosus. Gliocladium roseum decreased root length colonized when plants were 12 wk old, and T. pseudokoningii increased colonization of roots when plants were 4 wk old. Antagonistic, synergistic and neutral actions of G. mosseae upon the saprophytic fungi were observed. The population of T. harzianum decreased and the populations of T. pseudokoningii and SDM-54 increased in the presence of G. mosseae. Our results indicate a complex interaction between G. mosseae and associated saprophytic fungi.     

Xyloglucanases in the interaction between saprobe fungi and the arbuscular mycorrhizal fungus Glomus mosseae

We studied the production of xyloglucanase enzymes of pea and lettuce roots in the presence of saprobe and arbuscular mycorrhizal (AM) fungi. The AM fungus Glomus mosseae and the saprobe fungi Fusarium graminearum, Fusarium oxysporum-126, Trichoderma harzianum, Penicillium chrysogenum, Pleurotus ostreatus and Aspergillus niger were used. G. mosseae increased the shoot and root dry weight of pea but not of lettuce. Most of the saprobe fungi increased the level of mycorrhization of pea and lettuce, but only P. chrysogenum and T. harzianum inoculated together with G. mosseae increased the dry weight of pea and lettuce respectively. The AM and saprobe fungi increased the production of xyloglucanases by plant roots. The level of xyloglucanase activities and the number of xyloglucanolytic isozymes in plants inoculated with G. mosseae and most of the saprobe fungi tested were higher than when both microorganisms were inoculated separately. The possible relationship between xylogucanase activities and the ability of AM and saprobe fungi to improve the dry weight and AM root colonization of plants was discussed.     

Characterization of fungal 17beta-hydroxysteroid dehydrogenases

To promote understanding of the evolution of the steroid hormone signalling and hydroxysteroid dehydrogenases (HSDs), comparative characterization of fungal 17beta-HSDs was performed. Constitutive 17beta-HSD activity was determined in cytosols of the fungi: Cochliobolus lunatus, Pleospora herbarum, Fusarium lini, Trichoderma viride, Mucor spinosus, Rhizopus nigricans and Pleurotus ostreatus. The reaction equilibrium in all species except P. ostreatus was shifted towards reduction. The preferential coenzyme for reduction of androstenedione was NADPH, while for oxidation of testosterone, NAD4 was preferred. The highest enzyme activities were found in the Ascomycete C. lunatus (152.4 nmol mg(-1) h(-1)) and in the Basidiomycete P. ostreatus (69.1 nmol mg(-1) h(-1)). No similarities on the protein and mRNA level between fungal 17beta-HSDs and the purified enzyme from C. lunatus were observed. To investigate the nature of these enzymes, 17beta-HSD was purified from P. ostreatus using ammonium sulphate precipitation, hydrophobic interaction chromatography, and affinity chromatography. The purified enzyme has an apparent molecular mass of approximately 35 kDa and is probably a dimer as determined by gel filtration. Chemical modifications exposed Lys, His and Tyr as important for enzyme activity. Additionally, no similarities of C. lunatus and P. ostreatus enzymes were found to bacterial 3alpha,20beta-HSD from Streptomyces hydrogenans, 3beta,17beta-HSD from Comamonas testosteroni and mammalian 17beta-HSD types 1 and 4. The results thus suggest that there are most probably different enzymes responsible for 17beta-HSD activity in filamentous fungi.     

Biodegradation of endocrine-disrupting phthalates by Pleurotus ostreatus

Biodegradation of endocrine-disrupting phthalates [diethyl phthalate (DEP), dimethyl phthalate (DMP), butylbenzyl phthalate (BBP)] was investigated with 10 white rot fungi isolated in Korea. When the fungal mycelia were added together with 100 mg/l of phthalate into yeast extract-malt extract-glucose (YMG) medium, Pleurotus ostreatus, Irpex lacteus, Polyporus brumalis, Merulius tremellosus, Trametes versicolor, and T. versicolor MrP1 and MrP13 (transformant of the Mn-repressed peroxidase gene of T. versicolor) could remove almost all of the 3 kinds of phthalates within 12 days of incubation. When the phthalates were added to 5-day pregrown fungal cultures, most fungi except I. lacteus showed the increased removal of the phthalates compared with those of the nonpregrown cultures. In both culture conditions, P. ostreatus showed the highest degradation rates for the 3 phthalates tested. BBP was degraded with the highest rates among the 3 phthalates by all fungal strains. Only 14.9% of 100 mg/l BBP was degraded by the supernatant of P. ostreatus culture in YMG medium in 4 days of incubation, but the washed or homogenized mycelium of P. ostreatus could remove 100% of BBP within 2 days even in distilled water, indicating that the initial BBP biodegradation by P. ostreatus may be attributed to mycelium-associated enzymes rather than extracellular enzymes. The biodegradation rate of BBP by the immobilized cells of P. ostreatus was almost the same as that in the suspended culture. The estrogenic activity of 100 mg/l DMP decreased during biodegradation by P. ostreatus.     

Decolorization and detoxication of reactive industrial dyes by immobilized fungi <Emphasis Type="Italic">Trametes pubescens</Emphasis> and <Emphasis Type="Italic">Pleurotus ostreatus</Emphasis>

Trametes pubescens and Pleurotus ostreatus, immobilized on polyurethane foam cubes in bioreactors, were used to decolorize three industrial and model dyes at concentrations of 200, 1000 and 2000 ppm. Five sequential cycles were run for each dye and fungus. The activity of laccase, Mn-dependent and independent peroxidases, lignin peroxidase, and aryl-alcohol oxidase were daily monitored during the cycles and the toxicity of media containing 1000 and 2000 ppm of each dye was assessed by the Lemna minor (duckweed) ecotoxicity test. Both fungi were able to efficiently decolorize all dyes even at the highest concentration, and the duckweed test showed a significant reduction (p 相似文献   

Production of lignocellulose-degrading enzymes and changes in soil bacterial communities during the growth ofPleurotus ostreatus in soil with different carbon content

The extracellular enzyme activity and changes in soil bacterial community during the growth of the ligninolytic fungus Pleurotus ostreatus were determined in nonsterile soil with low and high available carbon content. In soil with P. ostreatus, the activity of ligninolytic enzymes laccase and Mn-peroxidase was several orders of magnitude higher than in soil without the fungus. Addition of lignocellulose to soil increased the activity of cellulolytic fungi and the production of Mn-peroxidase by P. ostreatus. The counts of heterotrophic bacteria were more significantly affected by the presence of lignocellulose than by P. ostreatus. The effects of both substrate addition and time (succession) were more significant factors affecting the soil bacterial community than the presence of P. ostreatus. Bacterial community structure was affected by fungal colonization in low carbon soil, where a decrease of diversity and changes in substrate utilization profiles were detected.     

Evaluation of white-rot fungi for detoxification and decolorization of effluents from the green olive debittering process

Wastewater produced by the debittering process of green olives (GOW) is rich in polyphenolics and presents high chemical oxygen demand and alkalinity values. Eight white-rot fungi ( Abortiporus biennis, Dichomitus squalens, Inonotus hispidus, Irpex lacteus, Lentinus tigrinus, Panellus stipticus, Pleurotus ostreatus and Trametes hirsuta) were grown in GOW for 1 month and the reduction in total phenolics, the decolorization activity and the related enzyme activities were compared. Phenolics were efficiently reduced by P. ostreatus (52%) and A. biennis (55%), followed by P. stipticus (42%) and D. squalens (36%), but only P. ostreatus had high decolorization efficiency (49%). Laccase activity was the highest in all of the fungi, followed by manganese-independent peroxidase (MnIP). Substantial manganese peroxidase (MnP) activity was observed only in GOW treated with P. ostreatus and A. biennis, whereas lignin peroxidase (LiP) and veratryl alcohol oxidase (VAOx) activities were not detected. Early measurements of laccase activity were highly correlated ( r(2)=0.91) with the final reduction of total phenolics and could serve as an early indicator of the potential of white-rot fungi to efficiently reduce the amount of total phenolics in GOW. The presence of MnP was, however, required to achieve efficient decolorization. Phytotoxicity of GOW treated with a selected P. ostreatus strain did not decline despite large reductions of the phenolic content (76%). Similarly, in GOW treated with purified laccase from Polyporus pensitius, a reduction in total phenolics which exceeded 50% was achieved; however, it was not accompanied by a decline in phytotoxicity. These results are probably related to the formation of phenoxy radicals and quinonoids, which re-polymerize in the absence of VAOx but do not lead to polymer precipitation in the treated GOW.     

Changes in the activities of enzymes involved in the degradation of butylbenzyl phthalate by Pleurotus ostreatus

Degradation of butylbenzyl phthalate (BBP) by the white rot fungus Pleurotus ostreatus and the activities of some degrading enzymes were examined in two different media containing 100 mg/l of the compound. P. ostreatus pregrown for 7 days in complex YMG medium was able to completely degrade BBP within an additional 24 h but degraded only 35 mg/l of BBP in 5 days of incubation in minimal medium. Fungal cell mass in the culture in YMG medium was higher in the presence than in the absence of BBP. The esterase activity of the fungal culture in YMG medium was higher than that in minimal medium and increased with the addition of BBP. On the contrary, laccase activity was higher in minimal medium and it did not increase upon the addition of BBP. General peroxidase activity increased for a few days after the addition of BBP to both media. The degradation of BBP and its metabolites by P. ostreatus thus may be attributed mostly to esterase rather than lignin-degrading laccase. In addition, the activities of the enzymes involved in BBP degradation and their changes varied significantly in the different media and culture conditions.     

Variations of lignocellulosic activities in dual cultures of Pleurotus ostreatus and Trichoderma longibrachiatum on unsterilized wheat straw

Trichoderma spp., soil filamentous fungi, are antagonists that can cause great losses in mushroom production. We have investigated the influence of T. longibrachiatum on the production of lignocellulolytic enzymes by Pleurotus ostreatus during its vegetative growth on a straw-based cultivation substrate that either had been sterilized, pasteurized or not heat treated. The variations in the lignocellulolytic activities and the electrophoretic patterns in single and dual cultures were used as a tool for perturbation assessment. The various heat treatments of the wheat straw before inoculation affected both the bacterial populations and the abilities of T. longibrachiatum and P. ostreatus to colonize the substrate and to produce extracellar lignocellulolytic enzymes. Interactions between T. longibrachiatum and the microflora of the substrate led to a great decrease of hydrolytic activities due to reduced colonization of the substrate. Pleurotus ostreatus also was affected but it was less sensitive than T. longibrachiatum. As a consequence, in dual cultures with P. ostreatus, the competitive ability of T. longibrachiatum was reduced by bacteria in the substrates. The presence of total microflora or thermotolerant microflora increased the production of phenoloxidase activities by P. ostreatus, despite reduced colonization of the substrate. This contributed to the improvement of the competitive ability of P. ostreatus in the pasteurized substrate. Furthermore, a direct effect of bacteria on T. longibrachiatum also was observed. In sterilized substrate, both laccase and Mn-peroxydase activities were increased dramatically in dual cultures due to a faster production of a laccase isoform, which was stimulated by T. longibrachiatum.     

Evaluation of two wild types of Pleurotus ostreatus (MCC07 and MCC20) isolated from nature for their ability to decolorize Benazol Black ZN textile dye in comparison to some commercial types of white rot fungi: Pleurotus ostreatus, Pleurotus djamor, and Pleurotus citrinopileatus

Biological decolorization of Benazol Black ZN, a reactive azo-type textile dyestuff, was comparatively studied using 3 different commercial-type white rot fungi strains (Pleurotus ostreatus, Pleurotus cornucopiae var. citrinopileatus, Pleurotus djamor, and 2 wild types of P. ostreatus (MCC07 and MCC20) isolated from the nature. The initial dye concentrations in the medium were 500 and 1000 mg.L-1. All the organisms studied decolorized Benazol Black ZN to varying degrees. At low dye concentration, both commercial and wild type of P. ostreatus resulted in the best decolorization, conversely, wild-type P. ostreatus (MCC07) was found to be much more robust against increasing dye concentration and provided the best decolorization efficiency at high dye concentration.     

Lignocellulose degradation by Pleurotus ostreatus in the presence of cadmium

Activities of cellulolytic and hemicellulolytic enzymes endo-1,4-beta-glucanase, exo-1,4-beta-glucanase, 1,4-beta-glucosidase, endo-1,4-beta-xylanase, 1,4-beta-xylosidase and 1,4-beta-mannosidase and ligninolytic enzymes Mn-peroxidase and laccase were detected during the growth of the white-rot fungus Pleurotus ostreatus on wheat straw in the presence and absence of cadmium. The loss of substrate dry weight and Mn-peroxidase activity decreased with increasing Cd concentration, whereas the activities of endo-1,4-beta-glucanase, 1,4-beta-glucosidase and laccase were highly increased in the presence of metal. The onset of hemicellulose-degrading enzyme activity was delayed in the presence of cadmium. The degradation of a model synthetic dye Poly B-411 did not correspond to the activities of ligninolytic enzymes. This is the first report about 1,4-beta-mannosidase in P. ostreatus.     

Tritrophic interactions in a soil community enhance decomposition rates

Microbivorous soil fauna can influence decomposition rates by regulating biomass and composition of the microbial community. The idea that predators at higher trophic levels regulate population densities of microbivorous fauna and thus indirectly increase microbial growth and activity has often been suggested but rarely examined in soil ecosystems. In this paper the effects of tritrophic interactions on decomposition processes in the soil are studied and expressed as soil respiration, hyphal lengths, cellulase and chitinase activities. The experiments were carried out in soil microcosms in a factorial design with three fungal species ( Alternaria alternata , Fusarium oxysporum , Trichoderma viride ), the fungivorous collembolan Folsomia fimetaria and the predatory mite Hypoaspis aculeifer . The respiration rate was significantly higher with three trophic levels than in those with two and lowest in those with only fungi present. This indicates that a low level of grazing stimulates microbial respiration more than a high level or no grazing at all. The effect was similar for all three fungal species but most pronounced in microcosms with the fungus A. alternata which was a preferred food source by the collembolans. Hyphal lengths were in all cases but with T. viride reduced in the presence of collembolans and predatory mites. T. viride had a slightly higher chitinase activity than the other fungi but increased numbers of trophic levels did not affect the enzymatic activities of any of the fungi.     

Extracellular oxidative enzyme production and PAH removal in soil by exploratory mycelium of white rot fungi

Selected strains of three species of white rot fungi, Pleurotus ostreatus, Phanerochaete chrysosporium and Trametes versicolor, were grown in sterilized soil from straw inocula. The respective colonization rates and mycelium density values decreased in the above mentioned order. Three- and four-ringed PAHs at 50 ppm inhibited growth of fungi in soil to some extent. The activities of fungal MnP and laccase (units per g dry weight of straw or soil), extracted with 50 mM succinate-lactate buffer (pH 4.5), were 5 to 20-fold higher in straw compared to soil. The enzyme activities per g dry soil in P. ostreatus and T. versicolor were similar, in contrast to P. chrysosporium, where they were extremely low. Compared to the aerated controls, P. ostreatus strains reduced the levels of anthracene, pyrene and phenanthrene by 81–87%, 84–93% and 41–64% within 2 months, respectively. During degradation of anthracene, all P. ostreatus strains accumulated anthraquinone. PAH removal rates in P. chrysosporium and T. versicolor soil cultures were much lower.     

强力安对食用菌生产中杂菌的毒力测定

试验利用滤纸片、管碟抑菌圈法测定了强力安杀菌剂对木霉TrichodermaviridePers.exFr、链孢霉MoniliasitophilaMont等食用菌生产上的杂菌的毒力,结果表明强力安具有明显的抑菌、杀菌作用。试验还测定了强力安对食用菌的作用,结果表明强力安对平菇Pleurotusostreatus(JacexFr)Quel、金针菇Flammulinavelutipes（Fr）Sing具抑制力,而对黑木耳Auriculariaauricula(l.exHook)Underw、香菇Lentinulaedodes(Berk)Pegler则未发现抑制作用。根据强力安对供试菌的最低抑制浓度,作者提出了生产实际上的用药浓度,以供参考。     

Mobilizing agents enhance fungal degradation of polycyclic aromatic hydrocarbons and affect diversity of indigenous bacteria in soil

The impact of several mobilizing agents (MAs) (i.e., soybean oil, Tween-20, Tween-80, olive-oil mill wastewaters, and randomly methylated beta-cyclodextrins) on the degradation performances of the white-rot fungi Irpex lacteus and Pleurotus ostreatus was comparatively assessed in a soil spiked with a mixture of seven polycyclic aromatic hydrocarbons (PAHs). Among the different MAs, soybean oil best supported the growth of both fungi that was twice that observed in soil in the absence of MAs. In addition, soybean oil positively affected PAH degradation by both fungi. In this case, the total weight of organic contaminants (TWOC) was lower than that in the absence of MAs (57.7 vs. 201.3 and 26.3 vs. 160.4 mg kg(-1) with I. lacteus and P. ostreatus, respectively). On the other hand, the number of cultivable heterotrophic bacteria was significantly lower in the soil with soybean oil augmented with either one of the two fungi (5.21 vs. 8.71 and 0.22 vs. 0.51 x 10(7) CFU g(-1) soil with I. lacteus and P. ostreatus, respectively). The effect of soybean oil was confirmed by denaturing gradient gel electrophoresis (DGGE) analysis of PCR-amplified 16S rRNA genes that showed a general decrease in biodiversity. The impact of the other MAs on bacterial diversity was either slightly negative or positive in incubation controls. Both richness and Shannon-Weaver index decreased upon treatment with P. ostreatus. Moreover, with this fungus the composition of the indigenous bacteria was not significantly affected by the type of MA used. By contrast, both indices increased in soil with I. lacteus in the presence of randomly methylated beta-cyclodextrins (39 vs. 33 and 1.43 vs. 1.26, respectively) and soybean oil (19 vs. 5 and 1.01 vs. 0.65, respectively).     

Bioremediation of Soil Contaminated with Explosives at the Naval Weapons Station Yorktown

The explosives TNT, HMX, and RDX are integral components of many munitions. The wastes from the manufacture and the use of these and other explosives has resulted in substantial contamination of water and soil. White rot fungi have been proposed for use in the bioremediation of contaminated soil and water. Strains of Phanerochaete chrysosporium and Pleurotus ostreatus adapted to grow on high concentrations of TNT were studied with regard to their ability to degrade TNT in liquid cultures. Both strains were able to cause extensive degradation of TNT. Field bioremediation studies using P. ostreatus were performed on site at the Yorktown Naval Weapons Station Yorktown (Yorktown, VA). In two plots, 6 cubic yards of soil contaminated with TNT, HMX, and RDX were blended with 3 cubic yards of a substrate mixture containing nutrients that promote the growth of fungi. In soil amended with growth substrate and P. ostreatus, concentrations of TNT, HMX and RDX were reduced from 194.0±50, 61±20 mg/kg and 118.0±30 to 3±4, 18±7 and 5±3?mg/kg, respectively, during a 62-day incubation period. Interestingly, in soil that was amended with this substrate mixture, but not with P. ostreatus, the concentrations of TNT, HMX, and RDX were also reduced substantially from 283±100, 67±20, and 144±50?mg/kg to 10±10, 34±20, and 12±10?mg/kg, respectively, during the same period. Thus, it appears that addition of amendments that enhance the growth and activity of indigenous microorganisms was sufficient to promote extensive degradation of these compounds in soil.     

Temperature affects the production,activity and stability of ligninolytic enzymes in<Emphasis Type="Italic">Pleurotus ostreatus</Emphasis> and<Emphasis Type="Italic">Trametes versicolor</Emphasis>

Enzyme activity was determined in cultures of Pleurotus ostreatus and Trametes versicolor with cellulose as a sole C source and high C/N ratio. The fungi were able to grow and produce laccase and Mn-peroxidase (MnP) at 5-35 degrees C, the highest production being recorded at 25-30 degrees C in P. ostreatus and at 35 degrees C in T. versicolor. Production of both enzymes at 10 degrees C accounted only for 4-20% of the maximum value. Temperature optima for enzyme activity were 50 and 55 degrees C for P. ostreatus and T. versicolor laccases, respectively, and 60 degrees C for MnP. Temperatures causing 50% loss of activity after 24 h were 32 and 47 degrees C for laccases and 36 and 30 degrees C for MnP from P. ostreatus and T. versicolor, respectively.     

Culture Age, Temperature, and pH Affect the Polyol and Trehalose Contents of Fungal Propagules

The growth and conidial physiology of the entomopathogenic fungi Beauveria bassiana, Metarhizium anisopliae, and Paecilomyces farinosus were studied under different conditions. The effects of culture age (up to 120 days), temperature (5 to 35(deg)C), and pH (2.9 to 11.1) were determined. Growth was optimal at pH 5 to 8 for each isolate and between 20 and 35(deg)C, depending on the isolate. The predominant polyol in conidia was mannitol, with up to 39, 134, and 61 mg g of conidia(sup-1) for B. bassiana, M. anisopliae, and P. farinosus, respectively. Conidia of M. anisopliae contained relatively small amounts of lower-molecular-weight polyols and trehalose (less than 25 mg g(sup-1) in total) in all treatments. Conidia of B. bassiana and P. farinosus contained up to 30, 32, and 25 mg of glycerol, erythritol, and trehalose, respectively, g(sup-1), depending on the treatment. Conidia of P. farinosus contained unusually high amounts of glycerol and erythritol at pH 2.9. The apparent effect of pH on gene expression is discussed in relation to the induction of a water stress response. To our knowledge, this is the first report of polyols and trehalose in fungal propagules produced over a range of temperature or pH. Some conditions and harvesting times were associated with an apparent inhibition of synthesis or accumulation of polyols and trehalose. This shows that culture age and environmental conditions affect the physiological quality of inoculum and can thereby determine its potential for biocontrol.     

驱避色防治平菇蚊、蝇类害虫的效果评价

为探讨运用驱避色防治平菇Pleurotus ostreatus蚊、蝇类害虫的可行性,本研究基于一种对平菇双翅目害虫具明显驱避作用的浅灰色（RGB=169, 169, 169）用于设计菌袋、地膜和棚膜,以评估这种驱避色赋能平菇配套栽培设施（菌袋、地膜和棚膜）对平菇蚊、蝇类害虫的驱避效果和增产作用。采用正交设计各影响因子处理组合进行田间小区试验,研究不同菌袋、地膜、棚膜颜色对害虫驱避率及平菇增产率的影响,筛选出最优组合,应用于生产实际。结果表明,驱避色菌袋+驱避色地膜+透明棚膜的处理组合的害虫驱避率和增产率均最高,与对照组相比,驱避率增加了45.63%,第1、2、3潮菇产量和总产量分别增加了11.29%,2.55%,8.82%和7.74%。通过多因素和差异显著性分析,菌袋颜色是影响害虫驱避率和增产率的主因子,与对照相比对害虫驱避率和前3潮菇增产率差异达到极显著水平。在平菇生产过程中,使用驱避色菌袋和地膜能有效控制平菇蚊、蝇类害虫的危害并提高产量,是一项值得推广的害虫防治措施。     

重金属Cd、Zn、Cu、Pb对土壤微生物和酶活性的影响

采用室内培养实验(25℃),研究了不同培养时间下重金属Cd、Zn、Cu、Pb(浓度分别为50,800,400,800mg.kg-1)污染对土壤微生物和酶活性的影响。结果表明,土壤蔗糖酶、过氧化氢酶和脱氢酶活性随着培养时间的增加而显著下降,在培养20d的时候达到最小值,然后酶活性缓慢升高。Cu对脲酶活性以及Cd对酸性磷酸酶和脲酶活性的抑制作用随时间增加而增加。土壤微生物生物量碳、细菌、真菌和放线菌数量随培养时间的增加均表现出先降低后升高的变化趋势。Cd和Cu对微生物生物量氮的抑制作用则随着培养时间的增加而增强,在培养30d时微生物生物量氮到达最低值,分别较培养10天减少了12.6%和16.5%。