[Dynamic Changes in Antibiotic Resistance Genes During Biological Fermentation of Chicken Manure and Pig Manure].

Livestock manure is a major carrier that stores and transmits antibiotic resistance genes (ARGs). The aim of this study was to identify the crucial environmental factors that result in the change in relative abundance of ARGs and MGEs to explore effective methods to reduce the occurrence of ARGs. The abundance of ten ARGs and five MGEs were measured using real-time quantitative PCR with 0, 3, 7, 10, 14, 21, 28, 45, 60, and 75 d in CM and PM aerobic composting. The succession law of the bacterial community was analyzed using 16S rRNA high-throughput sequencing. Furthermore, the abundance of ARGs and MGEs was correlated with the properties (temperature, moisture content, pH, and DOC) of composting piles to identify the crucial factors affecting the variation in ARGs and MGEs. The results showed that the abundance of ARGs and MGEs in PM was higher than that in CM. Composting significantly reduced the relative abundance of nine ARGs and five MGEs. The removal ratios of three ARGs (tetM, tetT, and aacA) and four MGEs (ISEcp1, IS1216, IS613, and tnp614) in CM reached 99%. The removal ratios of nine ARGs[tetB(P), tetL, tetM, tetO, tetT, aacA, aadD,aphA3, and sat4] and four MGEs (ISEcp1, IS26, IS1216, and tnp614) reached 99% in PM. However, the abundance of the genes tetG, intI1, and IS6100 increased. Firmicutes and Actinobacteria were dominant in CM and PM during composting. Actinobacteria and Proteobacteria may have been the major host bacteria of tetG and intI1. The redundancy analysis showed that moisture and pH were the crucial factors that could influence the differences in the abundance of ARGs and MGEs. The composition and abundance of ARGs were driven by physicochemical properties, bacterial community, and MGEs. Composting could significantly reduce the abundance of ARGs in CM and PM, thus reducing the risk of ARGs being distributed via livestock manure application. However, some ARGs and MGEs remained in high abundance. Therefore, it is necessary to further optimize the composting process, improve the harmless treatment effect of livestock manure, and promote the safe agricultural use of organic fertilizers.

[Effects of salinity on soil bacterial diversity and assembly processes in coastal soils.] / ç›åº¦å¯¹æ»¨æµ·åœŸå£¤ç»†èŒå¤šæ ·æ€§å’Œç¾¤è½æž„å»ºè¿‡ç¨‹çš„å½±å“.

Coastal saline soil is an important reserve resource of agricultural land. Soil microorganisms play a key role in soil nutrient cycling. However, it is still far from clear about the effects of salinity on soil microbial community. We examined the effects of salinity on soil bacterial abundance, diversity, and community assembly, by collecting soil samples in coastal areas with three salinity levels (non-, mild-, and severe-salinity). Our results showed that the activity of dehydrogenase and the abundance of bacteria significantly decreased in the severe-saline soils, while the diversity of bacteria remained unchanged, compared with non- and mild-saline soils. Bacterial communities were clustered by salinity. Null model was used to infer bacterial community assembly processes. Salinity was the main driving factor for bacterial community assembly. Deterministic process driven by salinity played a leading role in controlling bacterial community composition in coastal saline soil. These findings suggested that coastal saline soils contain abundant microbes within the salinity range, and have a biological basis for soil improvement. Due to the high deterministic process of microbial community assembly, it would be difficult for alien species to colonize coastal saline soils. Salt-tolerant and indigenous strains are recommended when using microbial technology to reclaim coastal saline soils.

Active Soil Nitrifying Communities Revealed by In Situ Transcriptomics and Microcosm-Based Stable-Isotope Probing.

Long-term nitrogen field fertilization often results in significant changes in nitrifying communities that catalyze a key step in the global N cycle. However, whether microcosm studies are able to inform the dynamic changes in communities of ammonia-oxidizing bacteria (AOB) and archaea (AOA) under field conditions remains poorly understood. This study aimed to evaluate the transcriptional activities of nitrifying communities under in situ conditions, and we found that they were largely similar to those of 13C-labeled nitrifying communities in the urea-amended microcosms of soils that had received different N fertilization regimens for 22 years. High-throughput sequencing of 16S rRNA genes and transcripts suggested that Nitrosospira cluster 3-like AOB and Nitrososphaera viennensis-like AOA were significantly stimulated in N-fertilized fresh soils. Real-time quantitative PCR demonstrated that the significant increase of AOA and AOB in fresh soils upon nitrogen fertilization could be preserved in the air-dried soils. DNA-based stable-isotope probing (SIP) further revealed the greatest labeling of Nitrosospira cluster 3-like AOB and Nitrosospira viennensis-like AOA, despite the strong advantage of AOB over AOA in the N-fertilized soils. Nitrobacter-like nitrite-oxidizing bacteria (NOB) played more important roles than Nitrospira-like NOB in urea-amended SIP microcosms, while the situation was the opposite under field conditions. Our results suggest that long-term fertilization selected for physiologically versatile AOB and AOA that could have been adapted to a wide range of substrate ammonium concentrations. It also provides compelling evidence that the dominant communities of transcriptionally active nitrifiers under field conditions were largely similar to those revealed in 13C-labeled microcosms.IMPORTANCE The role of manipulated microcosms in microbial ecology has been much debated, because they cannot entirely represent the in situ situation. We collected soil samples from 20 field plots, including 5 different treatments with and without nitrogen fertilizers for 22 years, in order to assess active nitrifying communities by in situ transcriptomics and microcosm-based stable-isotope probing. The results showed that chronic N enrichment led to competitive advantages of Nitrosospira cluster 3-like AOB over N. viennensis-like AOA in soils under field conditions. Microcosm labeling revealed similar results for active AOA and AOB, although an apparent discrepancy was observed for nitrite-oxidizing bacteria. This study suggests that the soil microbiome represents a relatively stable community resulting from complex evolutionary processes over a large time scale, and microcosms can serve as powerful tools to test the theory of environmental filtering on the key functional microbial guilds.

Bacillus fengqiuensis sp. nov., isolated from a typical sandy loam soil under long-term fertilization.

A Gram-staining-positive, endospore-forming, moderately alkaliphilic bacterium, strain NPK15(T), was isolated from a typical sandy loam soil under long-term NPK fertilization in northern China and was subjected to a polyphasic taxonomic study. The diamino acid of the cell-wall peptidoglycan of strain NPK15(T) was found to be meso-diaminopimelic acid and the cell-wall sugars were xylose, glucose and traces of mannose. The only respiratory quinone found in strain NPK15(T) was menaquinone 7 (MK-7). The major cellular fatty acids were iso-C(15 : 0), anteiso-C(15 : 0), C(16 : 0) and C(16 : 1)ω6c/C(16 : 1)ω7c. The major polar lipids were diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylglycerol. Phylogenetic analysis of the strain based on its 16S rRNA gene sequence showed that it was related most closely to 'Bacillus thaonhiensis' KACC 17216 (99.59%), B. songklensis KCTC 13881(T) (99.52%) and B. abyssalis CCTCC AB 2012074(T) (99.00%). DNA-DNA hybridization results indicated that the strain was distinct from other species of the genus Bacillus, the degree of relatedness being 35.4% with B. abyssalis CCTCC AB 2012074(T), 39.7% with B. songklensis KCTC 13881(T) and 51.2% with 'B. thaonhiensis' KACC 17216. The DNA G+C content of strain NPK15(T) was 45.5 mol%. Phenotypic, chemotaxonomic and molecular analyses identified strain NPK15(T) as a member of a novel species of the genus Bacillus, for which the name Bacillus fengqiuensis sp. nov. is proposed. The type strain is NPK15(T) ( = DSM 26745(T) = CCTCC AB 2013156(T)).

[Response of soil microbial community to the bioremediation of soil contaminated with PAHs].

The diversity of bacterial community in soil contaminated with polycyclic aromatic hydrocarbons (PAHs) was investigated during the plant-microbe remediation enhanced by biosurfactant rhamnolips (RH), using the polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) method. The results showed that Shannon-Weaver diversity index was only 3.17 before bioremediation, and increased to 3.24-3.45 after bioremediation, in particular, highest value was found in the treatment of alfalfa (AL) inoculated with arbuscular mycorrhizal fungi (AM) and PAHs-degrading bacteria (DB) among all the treatments. The clustering analysis showed that the similarities of soil bacterial community of AL, AL + RH, AL + AM and AL + AM + RH were above 90%. At the same time, the similarity of AL + DB was much closer to those of the four treatments mentioned above. Additionally, when the bacterial communities of AL + DB + RH, AL + DB + AM and AL + DB + AM + RH were grouped together, the similarities of these three treatments were also higher than 80%. By sequence alignment, it was found that the predominant and characteristic bands in DGGE patterns were closely related with PAHs-degrading bacteria, such as Bacillus, Pseudomonas, Acidobacteria, Sphingmonas, Rhodopseudomonas, Firmicutes, and Methylocytaceae. Application of rhamnolipids in plant-microbe bioremediation not only improved the bioavailability of PAHs, but also had a simultaneous influence on the diversity of soil bacterial community, resulting in the efficient promotion of PAHs removal from soils.

[Construction of Hg(2+)-induced luminescent reporter gene system and its application to detect mercury in red soil].

A luminescent reporter gene system was constructed by fusing the mercury-inducible promoter, P(merT), and its regulatory gene, merR with a promoterless reporter gene EGFP. A stable whole-cell reporter was created by mini-Tn5 and introducing the merR-egfp system cassette into the chromosome of Pseudomonas putida strain, then applied it for mercury detection in the red soil of Jiangxi province, the fluorescence density of the sensor strain was confirmed in soil extraction and fluorescence intensity was quantified by flow cytometry. The results showed positive correlation with the mercury pollutant in the concentration range of 0.04-50 mg x kg(-1). The background heavy metal irons such as Cr2+, Zn2+, Co2+, Cu2+, Pb2+, Ag+ at certain level did not interfere with the measurement. The key factor for detecting the fluorescence density was the induction time and the optimal temperature for EGFP expression was 30-35 degrees C. Spiked with 0.1 mg x kg(-1) Hg2+ and after 15 and 30 days incubation, red soil samples were extracted and evaluated water soluble, bioavailable, organic matter bound and residual fractions of mercury by both sensor strain and analytical way. The sensor strain appeared to have a detection range similar to that of atomic absorption spectroscopy (AAS) method and the effective detection ratio was 35%-64%.

[Interaction of biosurfactant-microorganism to enhance phytoremediation of aged polycyclic aromatic hydrocarbons (PAHS) contaminated soils with alfalfa (Medicago sativa L.)].

A pot experiment in greenhouse was carried out to investigate the interactive effect of rhamnolipids (RH) addition and PAHs-specific degrading bacteria (DB) inoculation on the phytoremediation efficiency for removal polycyclic aromatic hydrocarbons (PAHs) from agricultural soils. Results indicated that RH addition and DB inoculation promoted alfalfa (Medicago sativa L. ) growth and PAHs degradation in the soil. After 90 days, residual PAHs concentration in soil reduced 30.0% and 49.6% for the treatment of RH and DB, respectively, but only 21.7% for control. For the treatment of RH + DB, residual PAHs concentration in soil reduced 53.9%, showing synergy effect of RH addition and DB inoculation. In addition, the average PAHs degradation gradually reduced with the increase of the PAHs rings, but DB inoculation promoted the degradation of four-ring PAHs and five-ring PAHs. The number of PAHs degrading bacteria and dehydrogenase activity increased with the removal ratio of PAHs. Therefore RH addition and PAHs-specific degrading bacteria inoculation were effective in enhancing the phytoremediation efficiency of the long-term PAHs contaminated soils.

[Interactive effect of spent mushroom compost and rhamnolipids to enhance the efficiency of alfalfa remediation of aged PAHs contaminated soil].

Polycyclic aromatic hydrocarbons (PAHs) are a group of the most widespread organic pollutants, which distributed widely in soil and sediment. Pot experiment was conducted to improve efficiency of phytoremediation using alfalfa (Medicago sativa L.) in aged PAHs contaminated soil by introducing spent mushroom compost and rhamnolipids. Plant biomass, PAHs concentrations, number of soil microorganism, soil enzyme activity and soil microbial functional diversity were determined after 60 days of alfalfa growth. The results showed that within 60 days, removal ratio of PAHs in treatment of alfalfa alone (AL) reached to 14.43%, while removal ratio of PAHs in treatments of "GZ + RH0.5, + AL" and "GZ + RH1.0 + AL" reached to 32.64% and 36.95%, which were 115.45% and 156.06% higher than that of phytoremediation. Contrasted to the control, the treatment of "GZ + RH1.0 + AL" had more plant biomass than others, shoot and root dry weight were 1.05 g/pot and 0.20 g/pot, respectively. During the process of phytoremediation, the number of soil bacteria and fungi were greatly increased by "GZ + RH1.0 + AL" and reached to 31.37 x 10(6) CFU x g(-1) and 5.86 x 10(6) CFU x g(-1), especially the number of PAHs-degrading bacteria reached to 39.57 x 10(5) MPN x g(-1), which were 29 times more than control treatment and 4 times more than treatment of alfalfa alone (AL). Moreover, soil dehydrogenase activity and the functional diversity of soil microbial community were increased significantly by the treatment of "GZ + RH1.0 + AL", respectively. Therefore, interaction of spent mushroom compost and rhamnolipids to enhance the phytoremediation efficiency had satisfied results in removal aged PAHs from an agricultural soil, the feasibility of this method needed to be further proved by large-area scale field experiment.

[Arbuscular mycorrhizal fungal effects on wheat growth in response to elevated tropospheric O3 concentration].

A FACE (Free-air component enrichment) system in a rice/wheat rotation field was used to investigate the effects of arbuscular mycorrhizal fungal (AMF) inoculation on wheat growth and soil microbial biomass under elevated tropospheric O3 concentration. The elevated O3 concentration tended to increase AM colonization of wheat seedling and bate plant growth during the booting period, then significantly (p < 0.05) reduced aerial biomass, individual yield and kernel weight by 22%, 29% and 9%, respectively, and decreased soil microbial biomass N by 37% after wheat harvesting. However, the total N content in wheat grain significantly (p < 0.05) increased from 2.2% to 2.6%. Under elevated O3 concentration, AMF inoculation accelerated AM colonization successfully, and improved colonization rate and aerial biomass significantly (p < 0.05) during the booting period, thus reduced the damage of aerial biomass by 50% when harvesting, and increased soil microbial biomass N significantly (p < 0.05) related to the noninoculated treatment. Although wheat yield didn't increase, the total N content in grain decreased to the same level of that of the control wheat. It suggested that higher AM colonization is the resistance behavior of wheat in response to O3 intimidation, and AMF inoculation can accelerate wheat growth, increase root exudates and soil microbial biomass subsequencely.

[Spatiotemporal evolvement of soil microbiological characteristics in upland fields with different utilization duration in Cixi, Zhejiang Province].

The microbial number, microbial biomass, and enzymatic activities in five upland soils under agricultural utilization for 50-700 years were determined, with the correlations between soil microbiological characteristics and agricultural utilization duration analyzed. In the meantime, the functional diversity of microbes in soils having been utilized for 50, 100, and 700 years were investigated. The results showed that at the early stage (< 100 years) of agricultural utilization, the number of soil fungi (F) had a slight increase, while the bacterial number (B), B/F ratio, microbial biomass C (C(mic)), microbial biomass N (N(mic)), and the activities of catalase, invertase and urease all decreased markedly. After utilized for more than 100 years, the F decreased significantly, while the B, B/F ratio, C(mic), N(mic), and the activities of test enzymes all tended to increase. During the whole utilization period from 50 to 700 years, the C(mic)/N(mic) ratio had a significant increase with year. The Shannon, Simpson, and McIntosh indices of soil microbial community had the same responses to the agricultural utilization duration as the bacterial number, microbial biomass, and enzymatic activities. All of these indicated that in the upland fields in Cixi of Zhejiang Province, shifts of soil microbial community occurred with increasing agricultural utilization duration, and soil microbiological quality had an overall increase after 100 years agricultural utilization.

[Effects of earthworm (Eisennia foetida ) on As, P uptake by maize and As, P fractional transformation in the rhizosphere].

A pot experiment was conducted to examine the roles of earthworm in As uptake from original As-polluted soil by maize (Zea mays L.), and their effects on As, P fractions in the rhizosphere. The As-polluted soils with three As levels were collected from the arable soil near As mine. The plants were harvested after 10 weeks of growth. Dry weight (DW) and P, As concentrations of plants, as well as As and P fractions of the rhizospheric soil, were determined. The results showed that inoculated earthworm or appended rice straw increased maximal 149%, 222% DW of root and shoot, respectively. At the medium and high soil As levels, root As concentration in the soil treated by earthworm and rice straw was highest among all treatments, and earthworm increased more As concentration of shoot than rice straw did. In different soil As levels, root P concentration in the soil treated by earthworm was highest, and shoot P by rice straw. Ca-P affected maize absorbing As at the low soil As level(r = 0.981), and maize absorbing Al-P was restrained by As involved in well-crystallized hydrous oxides of Fe and Al at the medium (r = 0.953)and high (r = 0.997)soil As levels. The concentration of non-specially absorbed As and As combined with Fe or Al and of O-P increased at the soil inoculated earthworm or/and appended rice straw at the same time. These results indicated that earthworm was more valuable for plant developing than rice straw was.

Halomonas shengliensis sp. nov., a moderately halophilic, denitrifying, crude-oil-utilizing bacterium.

A moderately halophilic bacterium, designated strain SL014B-85(T), was isolated from a crude-oil-contaminated saline soil from Shengli oilfield, Shandong Province, China. Cells were Gram-negative, aerobic, short rods with lateral flagella. Growth occurred at NaCl concentrations of 0-15 % (optimum 5-15 %), at 10-42 degrees C (optimum 30 degrees C) and at pH 8.0-9.0 (optimum pH 8.5). The only respiratory quinone was Q9, and the main cellular fatty acids were C(18 : 1)omega7c, C(16 : 0) and C(19 : 0) cyclo omega8c. The G+C content of the DNA was 66.6 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain SL014B-85(T) belonged to the genus Halomonas in the Gammaproteobacteria, with highest sequence similarity of 98.1 and 97.8 % to Halomonas alimentaria DSM 15356(T) and Halomonas ventosae DSM 15911(T), respectively. DNA-DNA relatedness values were below 40 % with members of closely related Halomonas species. Results of phenotypic, biochemical and phylogenetic analyses revealed that strain SL014B-85(T) could be classified as representing a novel species of the genus Halomonas, for which the name Halomonas shengliensis sp. nov. is proposed. The type strain is SL014B-85(T) (=CGMCC 1.6444(T)=LMG 23897(T)).

Role of microbial inoculation and chitosan in phytoextraction of Cu, Zn, Pb and Cd by Elsholtzia splendens--a field case.

A field experiment was carried out to study the effect of microbial inoculation on heavy metal phytoextraction by Elsholtzia splendens and whether chitosan could have a synergistic effect with the microbial inocula. The microbial inocula consisted of a consortium of arbuscular mycorrhizal fungi and two Penicillium fungi. Three treatments were included: the control, inoculation with microbial inocula, and the inoculation combined with chitosan. Microbial inoculation increased plant biomass especially shoot dry weight, enhanced shoot Cu, Zn and Pb concentrations but did not affect Cd, leading to higher shoot Cu, Zn, Pb and Cd uptake. Compared with microbial inoculation alone, chitosan application did not affect plant growth but increased shoot Zn, Pb and Cd concentrations except Cu, which led to higher phytoextraction efficiencies and partitioning to shoots of Zn, Pb and Cd. These results indicated synergistic effects between microbial inocula and chitosan on Zn, Pb and Cd phytoextraction.

Effect of arbuscular mycorrhizal fungal inoculation on heavy metal accumulation of maize grown in a naturally contaminated soil.

A pot culture experiment was carried out to study heavy metal (HM) phytoaccumulation from soil contaminated with Cu, Zn, Pb, and Cd by maize (Zea mays L.) inoculated with arbuscular mycorrhizal (AM) fungi (AMF). Two AM fungal inocula--MI containing only one AM fungal strain (Glomus caledonium 90036) and MII consisting of Gigaspora margarita ZJ37, Gigaspora decipens ZJ38, Scutellospora gilmori ZJ39, Acaulospora spp., and Glomus spp.--were applied to the soil under unsterilized conditions. The control received no mycorrhizal inoculation. The maize plants were harvested after 10 wk of growth. MI-treated plants had higher mycorrhizal colonization than MII-treated plants. Both MI and MII increased P concentrations in roots, but not in shoots. Neither MI nor MII had significant effects on shoot or root dry weight (DW). Compared with the control, shoot Cu, Zn, Pb, and Cd concentrations were decreased by MI but increased by MII. Cu, Zn, Pb, and Cd uptake into shoots and roots all increased in MII-treated plants, while in MI-treated plants Cu, Zn, and Pb uptake into shoots and Cd uptake into roots decreased but Cu, Zn, and Pb uptake into roots and Cd into shoots increased. MII was more effective than MI in promoting HM extraction efficiencies. The results indicate that MII can benefit HMphytoextraction and, therefore, show potential in the phytoremediation of HM-contaminated soils.

[Distribution characteristics and sources identification of PAHs in ancient paddy soil].

Soil samples of current paddy soils, ancient paddy soil/ancient dry land soil, and bottom soils were collected from two sites in Chuodunshan Site of Majiabang Culture (about 6,000a). 15 polycyclic aromatic hydrocarbons (PAHs) were analyzed with HPLC, and their possible sources were identified. The sum of 15 PAHs was 202.9microg x kg(-1) and 207.7microg x kg(-1) in the surface soils from Site A and Site B respectively, which were mainly deposited from atmosphere. In ancient paddy soil from Site A, the total PAHs concentration sharply decreased to 56.0microg x kg(-1), but was still higher than those in ancient dry land soil and bottom soils with the sum of 32.0 approximately 36.9microg x kg(-1). In ancient paddy soil, the concentrations of 2-ring and 3-ring PAHs took a larger portion of 63 percents to the total PAHs, and naphthalene and phenanthrene were the most abundant compounds, while PAHs of more than 4 rings took a small part. The ratios of phenanthrene anthracene and benzo(a) anthracene chrysene and 13C-NMR spectrum of soil organic matter showed that PAHs in ancient paddy soil mainly originated from rice straw burning, biogenesis under reducing conditions may be another source.

[Influence of arbuscular Mycorrhizal fungi on growth and cu uptake of Elsholtzia splendens].

A pot culture experiment was carried out to study the influence of arbuscular mycorrhizal (AM) fungi on the growth and Cu uptake of E. splendens. Five levels of Cu (0, 50, 100, 200, 400mg x kg(-1)) and two AM fungal inocula, Glomus caledonium 90036 (36) and Acaulospora mellea ZZ (ZZ), and one nonmycorrhizal inoculum (CK), were applied to the soil under sterilized conditions. The plants were harvested after 60 days of growth. Although decreasing with the increase of Cu levels, root infection rates of all the mycorrhizal plants were >50%, which showed that AM fungi colonized E. splendens roots easily. Shoot and root dry matter yields were all increased by two AM inocula at all Cu levels. Shoot Cu concentrations in the plants treated with two AM inocula increased at 200mg x kg(-1) Cu level and below, but did not change significantly at 400mg x kg(-1) Cu level. Root Cu concentrations in the plants treated with two AM inocula did not change at 0 mg x kg(-1) Cu level, but decreased at 50 mg x kg(-1) Cu level and above. In comparison with nonmycorrhizal plants, shoot Cu uptake by mycorrhizal plants all increased at any Cu level, while root Cu uptake increased only at 100 mg x kg(-1) Cu level. In general, AM fungal inoculation can increase Cu translocation from roots to shoots and shoot Cu uptake by E. splendens.

Effect of inoculation with arbuscular mycorrhizal fungi on the degradation of DEHP in soil.

The effect of inoculation with arbuscular mycorrhizal (AM) fungi (Acaulospora lavis) on the degradation of di(2-ethylhexyl) phthalate (DEHP) in soil was studies. Cowpea plants (Pigna sinensis) were used as host plants and grown in a specially designed rhizobox. The experimental results indicated that, both in sterile and non-sterile soil, mycorrhizal colonization rates were much higher in the mycorrhizal plants than in the non-mycorrhizal plants. Addition of 4 mg/kg DEHP slightly affected mycorrhizal colonization, but the addition of 100 mg/kg DEHP significantly decreased mycorrhizal colonization. DEHP degradation in the mycorrhizosphere (Ms) and hyphosphere (Hs), especially in the Hs, increased after inoculation with Acaulospora lavis. It is concluded that mycorrhizal hyphae play an important role in the plant uptake, degradation and translocation of DEHP. The mechanism might be attributed to increased numbers of bacteria and actinomycetes and activity of dehydrogenase, urease and acid phosphatase in the Ms and Hs by mycorrhizal fungi.

Arbuscular mycorrhizal status of wild plants in saline-alkaline soils of the Yellow River Delta.

A survey was made of the arbuscular mycorrhizal (AM) status of five dominant wild plants Tamarix chinensis, Phragmites communis, Suaeda glauca, Aeluropus littoralis var. sinensis and Cirsium setosum in saline-alkaline soils of the Yellow River Delta that show low plant diversity. All of the species were colonized and showed typical AM structures (arbuscules, vesicles). The colonization percentage ranged from 0.2% to 9.5%, where C. setosum was the highest. The species richness of AMF at the different sites ranged from 2.00 to 2.40 per 50 ml soil, with an average of 2.16. Species diversity ranged from 1.99 to 2.22 per 50 ml soil, with an average of 2.13. Spore density ranged from 3 to 30 per 50 ml soil, with an average of 12. Glomus was the dominant genus, with a frequency and relative abundance of 88.1% and 68.4%, respectively. G. caledonium, with a frequency and relative abundance of 15.0% and 4.6%, respectively, was the dominant species. Differences were also observed in the distribution of AMF in different soil layers. Although there were still AM fungal spores in the layer 40 cm below the surface, most spores were found at a depth of 0-40 cm.