Comparisons of Mycorrhizal Responsiveness with Field Soil and Commercial Inoculum for Six Native Montane Species and Bromus tectorum

Reestablishing native perennial plants and reducing invasive species are pivotal for many ecological restoration projects. The interactions among plant species, arbuscular mycorrhizal fungi, and soil P availability may be critical determinants of the success of native and non‐native plants in restoration and species invasions. Here we assessed mycorrhizal responsiveness for three late‐successional and three early‐successional plant species native to Rocky Mountain National Park and for the non‐native Downy brome, cheatgrass (Bromus tectorum L.) using field soil and commercial inoculum. Factorial greenhouse experiments were conducted to compare biomass of plant species with and without field soil and commercial inoculum treatments along a phosphorus (P) gradient, which ranged from ambient field levels to 12% of field levels, using dilutions of native soils. The two field soil inoculum treatments resulted in significant biomass differences for all species studied. Late‐successional species responded positively to field inoculum, whereas early‐successional species responded negatively. The two commercial inocula had low colonization rates (14 of 166 inoculated plants). The commercial inocula substrates had significant treatment effects on five of seven species included in the study in the apparent absence of mycorrhizal symbiosis. Soil P levels influenced mycorrhizal responsiveness in only one species, Smooth blue aster (Aster laevis L.). Our results show that, at least for the species studied here, locally collected field inoculum is the best choice for reestablishment of late‐successional native plant species.     

Host Range of Australian Phoma ligulicola var. inoxydablis Isolates from Pyrethrum

Ray blight, caused by Phoma ligulicola var. inoxydablis is one of the most damaging diseases of pyrethrum ( Tanacetum cinerariifolium [Trevir.] Sch. Bip.) in Australia. The pathogenicity of P. ligulicola var. inoxydablis to a range of ornamental and other plant species was tested to determine potential sources of inoculum into pyrethrum crops. Differences were identified in the host range of P. ligulicola var. inoxydablis isolates in this study in comparison with isolates reported from garden chrysanthemum ( Chrysanthemum morifolium L.), most likely to be P. ligulicola var. ligulicola . Australian P. ligulicola var. inoxydablis isolates were unable to infect and cause disease following repeated inoculation to zinnia ( Zinnia elegans L.), sunflower ( Helianthus annuus L.), dahlia ( Dahlia variabilis Desf.), and several cultivars of crisphead lettuce ( Lactuca sativa L.). French marigold ( Tagetes patula L.) was recorded as a susceptible host for this pathogen for the first time. Moreover, the susceptibility of annual chrysanthemum ( Chrysanthemum carinatum L.) to infection by P. ligulicola var. inoxydablis was confirmed. Implications for disease management in Tasmanian pyrethrum fields are discussed.     

The roles of ascospores and conidia of Pyrenopeziza brassicae in light leaf spot epidemics on winter oilseed rape (Brassica napus) in the UK

Ascospores of Pyrenopeziza brassicae were produced in apothecia (cup‐shaped ascomata) on oilseed rape debris. The conidia, which were morphologically identical to the ascospores, were produced in acervular conidiomata was greater than for lesions caused by ascospores. In June 2000, on the ground under a crop with light on the surface of living oilseed rape tissues. Ascospores were more infective than conidia on oilseed rape leaves. The proportion of lesions caused by conidia located on leaf veins leaf spot, numbers of petioles with apothecia decreased with increasing distance into the crop from the edge of pathways. Air‐borne ascospores of P. brassicae were first collected above debris of oilseed rape affected with light leaf spot on 5 October 1998 and 18 September 1999,12 or 23 days, respectively, after the debris had been exposed outdoors. P. brassicae conidia were first observed on leaves of winter oilseed rape on 6 January 1999 and 15 February 2000, respectively, after plots had been inoculated with debris in November 1998 and October 1999. In 1991/92, numbers of ascospores above a naturally infected crop were small from January to April and increased in June and July. P. brassicae conidia were first observed in February and the percentage plants with leaves, stems or pods with light leaf spot increased greatly in May and June. In 1992/93, in a crop inoculated with debris, numbers of airborne ascospores were small from October to January and increased from April to June. P. brassicae conidia were first observed on leaves in late November and light leaf spot was seen on stems and pods in March and June 1993, respectively.     

Seasonal changes in primary and secondary inoculum during epidemics of leaf blotch (Rhynchosporium secalis) on winter barley

Seasonal changes in numbers of conidia of Rhynchosporium secalis on debris from previous barley crops infected with leaf blotch (primary inoculum) were monitored in 1985–86 and 1986–87. In 1986–87, changes in numbers of conidia on leaves of plants in the new winter barley crop (secondary inoculum) were also recorded. The greatest increases in production of primary inoculum were in early spring after rain, when temperatures were increasing after periods of sub-zero temperatures when there was little conidial production. Subsequently, more conidia were recovered from this debris after cycles of drying and rewetting than when it remained wet. After January 1987, amounts of secondary inoculum produced on the crop were much greater than amounts of primary inoculum on debris. Most spores were produced on the basal leaves and more spores were present on the September-sown than on the November-sown crop. Thus, while primary inoculum was a source of disease when plants were emerging, secondary inoculum on basal leaves was the main source of disease at stem extension, especially on early-sown crops.     

Impact of different densities of Neohydronomus affinis (Coleoptera:Curculionidae) on Pistia stratiotes (Araceae) under laboratory conditions

In Senegal, a laboratory study was conducted in 2005 to ascertain the effect that different numbers of the host-specific weevil Neohydronomus affinis Hustache (Coleoptera: Curculionidae) per plant had on selected plant growth parameters of its target weed, water lettuce Pistia stratiotes Linnaeus (Araceae). Compared to the control, the weevil caused a significant reduction in all parameters measured, except for daughter plant production. There were no significant differences in impact on the plant between the three different densities of weevil (one, two and three pairs per plant). Under laboratory conditions one pair per plant is deemed sufficient to effect complete control of water lettuce over a six-week period.     

Coinoculation of containerized Douglas-fir (Pseudotsuga menziesii) and maritime pine (Pinus pinaster) seedlings with the ectomycorrhizal fungi Laccaria bicolor and Rhizopogon spp.

 Coinoculations with mycelium of Laccaria bicolor and spores of Rhizopogon spp. included in alginate gel have been carried out to determine: (1) the ability of the mixed inoculum to produce dual-colonized containerized Douglas-fir and maritime pine planting stocks and (2) the colonization pattern of the two fungi in individual root systems. For both tree species, the maximal proportion of dual-colonized seedlings obtained almost never exceeded 50%. The rest of the seedlings remained colonized by a single fungus or were non-colonized. In Douglas-fir inoculations, the relationship between the dual-colonized seedlings obtained and the initial dose of the two fungi was highly significant. The highest proportion of dual-colonized seedlings was obtained when the highest dose of R. subareolatus was used (10⁶ spores/seedling), regardless of the dose of L. bicolor. Among the treatments producing 25% or more dual-colonized seedlings, differences in the proportion of Laccaria/Rhizopogon mycorrhizas and total root colonization percentages were not clearly related to the initial combination of doses. The proportion of dual-colonized maritime pine seedlings was not significantly related to the initial inoculation doses of the two fungi. The proportion of Laccaria/Rhizopogon mycorrhizas was not significantly different among treatments with 25% or more dual-colonized seedlings, whereas total colonization percentages ranged from 37% with the combination 0.08/10⁴ (g L. bicolor / spores R. roseolus per seedling) to 74% with the combination 0.08/10⁶, this difference being statistically significant. Accepted: 15 September 1998     

糖化酶生产菌株种子制备工艺优化

目的：缩短糖化酶工业生产菌株黑曲霉A.nigerCICIM GB0506的种子制备周期。方法：对该菌的活化培养基配方及种子制备方式进行改良,并通过L9（3^4）正交试验对其液体培养方法进行优化。结果：在固体活化培养基中添加0.2%的酵母粉及1%的玉米淀粉,有利于加速菌体生长;加入40粒,粒径3-4mm的玻璃珠130r/min,摇床培养可以获得更为分散、均一的种子液;液体种子制备的较优条件为初始pH4.5,装液量90mL,琼脂加量0.1%,培养天数5d。结论：新的制备工艺使糖化酶种子制备时间较现在工业生产上使用的工艺缩短了4d,进行后续糖化酶摇瓶发酵产酶水平是原工艺的1.18倍。     

Transient β-glucuronidase activity after infiltration of Arabidopsis thaliana by Agrobacterium tumefaciens

Transient expression of the β-glucuronidase (GUS) gene introduced into Arabidopsis thaliana intact plants by T-DNA after vacuum infiltration of Agrobacterium tumefaciens was followed. The first incidence of GUS activity was found 2 - 3 d after treatment and a peak of activity one week after treatment in both A. thaliana races, Columbia and C24. GUS activity was sharply increased by cultivation of Arabidopsis plants at elevated temperature (29 °C) compared to cultivation at 25 °C. The density of inocula also influenced the GUS activity. This revised version was published online in July 2006 with corrections to the Cover Date.     

Relationship between the number of bacteria added to soil or seeds and their abundance and distribution in the rhizosphere of alfalfa

A study was conducted of the relationship between the density of several bacterial strains introduced into soil or onto seeds and their abundance in the rhizosphere of alfalfa. The abundance of six species in the rhizosphere was directly correlated with the density of bacteria initially added to soil. The density of six species in the rhizosphere of 15-day-old plants also was directly correlated with the density of each strain in nonrhizosphere soil. Tests of seven species added to soil at four inoculum densities showed that bacteria that survived well in the soil attained the highest densities in the rhizosphere and those that survived poorly in the soil were present at the lowest densities in the rhizosphere. Sixteen of 19 bacterial strains added to alfalfa seeds at 10⁷ or 10⁸ cells per g colonized the rhizosphere of 15-day-old plants, but nearly all of the cells were localized in the upper third of the rhizosphere. A study of 12 bacterial strains that failed to colonize the lower part of the rhizosphere if inoculated onto seeds showed that the bacteria colonized the entire rhizosphere of 15-day-old alfalfa plants if initially inoculated throughout the soil. The data suggest that the density of individual bacterial strains in the rhizosphere is dependent on their density in the soil and that seed inoculation only has an effect on the population in the proximal portion of the alfalfa root system.     

Biological potential of fungal inocula for bioaugmentation of contaminated soils

The suitability of the fluorescein diacetate hydrolyzing activity (FDA) assay for determining the biological potential (ie fungal biomass produced per unit of substrate) of solid pelleted fungal inoculum intended for use in the bioaugmentation of contaminated soils with white-rot fungi, was evaluated. FDA activity of the white-rot fungusPhanerochaete chrysosporium grown on pelleted substrates and on agar was found to be proportional to quantities of fungal ergesterol and fungal dry matter, respectively. Inoculum biological potential was found to be greatly influenced by substrate formulation and structure, and temperature. Biological potential and the type of carrier influenced the ability ofP. chrysosporium to tolerate pentachlorophenol (PCP).Phanerochaete chrysosporium andTrametes versicolor introduced into PCP-contaminated soil on pellets with higher biological potential and higher nitrogen content (C:N ratio of 501), did not remove PCP more efficiently than when the fungi were introduced on pellets with a lower biological potential (C:N ratio of 3091). However, under the latter conditions most of the PCP was transformed to pentachloroanisole (PCA). In soil inoculated withT. versicolor on pellets with high biological potential, higher manganese peroxidase activity was detected compared to soil inoculated with pellets with a lower biological potential.     

Enhancement of plant growth by Zygorrhynchus moelleri

Cucumber, tomato, two flowering annuals and a flowering perennial produced plants of greater weight in soilless compost infested with Zygorrhynchus moelleri than in uninfested compost. In Z. moelleri -infested compost the annuals commenced flowering 4 to 10 days earlier, cucumbers produced mature fruits more rapidly and a greater weight (20%) of fruit was harvested from 15-wk-old tomato plants. Leaves of 11 and 15-wk-old tomato plants grown in infested compost contained more chlorophyll than leaves from plants in uninfested compost. Z. moelleri was isolated from 99% of segments cut from roots of tomato plants grown in infested compost and it suppressed the growth of Trichoderma spp. at the root surface. Propagules of Z. moelleri remained viable in air-dried compost for at least 12 months. In axenic culture, Z. moelleri enhanced lateral root development in tomato and cucumber seedlings.     

Timing and abundance of sporangia production and zoospore release influences the recovery of different Phytophthora species by baiting

Analysis of soil samples using High Throughput Sequencing (HTS) frequently detects more Phytophthora species compared with traditional soil baiting methods. This study investigated whether differences between species in the timing and abundance of sporangial production and zoospore release could be a reason for the lower number of species isolated by baiting. Stems of Eucalyptus marginata were inoculated with ten Phytophthora species (P. nicotianae, P. multivora, P. pseudocryptogea, P. cinnamomi, P. thermophila, P. arenaria, P. heveae, P. constricta, P. gondwanensis and P. versiformis), and lesioned sections for each species were baited separately in water. There were significant differences between species in timing of sporangia production and zoospore release. P. nicotianae, P. pseudocryptogea, P. multivora and P. thermophila released zoospores within 8–12 h and could be isolated from lesioned baits within 1–2 days. In contrast, P. constricta did not produce zoospores for over 48 h and was only isolated 5–7 days after baiting. P. heveae and P. versiformis did not produce zoospores and were not recovered from the baits. When species were paired in the same baiting tub, those that produced zoospores in the shortest time were isolated most frequently, while species slow to produce zoospores, or which produced them in lower numbers, were isolated from few baits or not at all. Thus, species differences in the timing of sporangia production and zoospore release may contribute to the ease of isolation of some Phytophthora species when they are present together with other Phytophthora species in an environmental sample.     

Early events in hepatitis B infection: the role of inoculum dose

The relationship between the inoculum dose and the ability of the pathogen to invade the host is poorly understood. Experimental studies in non-human primates infected with different inoculum doses of hepatitis B virus have shown a non-monotonic relationship between dose magnitude and infection outcome, with high and low doses leading to 100% liver infection and intermediate doses leading to less than 0.1% liver infection, corresponding to CD4 T-cell priming. Since hepatitis B clearance is CD8 T-cell mediated, the question of whether the inoculum dose influences CD8 T-cell dynamics arises. To help answer this question, we developed a mathematical model of virus–host interaction following hepatitis B virus infection. Our model explains the experimental data well, and predicts that the inoculum dose affects both the timing of the CD8 T-cell expansion and the quality of its response, especially the non-cytotoxic function. We find that a low-dose challenge leads to slow CD8 T-cell expansion, weak non-cytotoxic functions, and virus persistence; high- and medium-dose challenges lead to fast CD8 T-cell expansion, strong cytotoxic and non-cytotoxic function, and virus clearance; while a super-low-dose challenge leads to delayed CD8 T-cell expansion, strong cytotoxic and non-cytotoxic function, and virus clearance. These results are useful for designing immune cell-based interventions.     

Comparison of microbial community composition and activity in sulfate-reducing batch systems remediating mine drainage

Five microbial inocula were evaluated in batch tests for the ability to remediate mine drainage (MD). Dairy manure (DM), anaerobic digester sludge, substrate from the Luttrell (LUTR) and Peerless Jenny King (PJK) sulfate-reducing permeable reactive zones (SR-PRZs) and material from an MD-treatment column that had been inoculated with material from a previous MD-treatment column were compared in terms of sulfate and metal removal and pH neutralization. The microbial communities were characterized at 0, 2, 4, 9, and 14 weeks using denaturing gradient gel electrophoresis and quantitative polymerase chain reaction to quantify all bacteria and the sulfate-reducing bacteria of the genus Desulfovibrio. The cultures inoculated with the LUTR, PJK, and DM materials demonstrated significantly higher rates of sulfate and metal removal, and contained all the microorganisms associated with the desired functions of SR-PRZs (i.e., polysaccharide degradation, fermentation, and sulfate reduction) as well as a relatively high proportion of Desulfovibrio spp. These results demonstrate that inoculum influences performance and also provide insights into key aspects of inoculum composition that impact performance. This is the first systematic biomolecular examination of the relationship between microbial community composition and MD remediation capabilities.     

Long-term effect of inoculum pretreatment on fermentative hydrogen production by repeated batch cultivations: homoacetogenesis and methanogenesis as competitors to hydrogen production

Long-term effects of inoculum pretreatments (heat, acid, loading-shock) on hydrogen production from glucose under different temperatures (37 °C, 55 °C) and initial pH (7 and 5.5) were studied by repeated batch cultivations. Results obtained showed that it was necessary to investigate the long-term effect of inoculum pretreatment on hydrogen production since pretreatments may just temporarily inhibit the hydrogen consuming processes. After long-term cultivation, pretreated inocula did not enhance hydrogen production compared to untreated inocula under mesophilic conditions (initial pH 7 and pH 5.5) and thermophilic conditions (initial pH 7). However, pretreatment could inhibit lactate production and lead to higher hydrogen yield under thermophilic conditions at initial pH 5.5. The results further demonstrated that inoculum pretreatment could not permanently inhibit either methanogenesis or homoacetogenesis, and methanogenesis and homoacetogenesis could only be inhibited by proper control of fermentation pH and temperature. Methanogenic activity could be inhibited at pH lower than 6, both under mesophilic and thermophilic conditions, while homoacetogenic activity could only be inhibited under thermophilic condition at initial pH 5.5. Microbial community analysis showed that pretreatment did not affect the dominant bacteria. The dominant bacteria were Clostridium butyricum related organisms under mesophilic condition (initial pH 7 and 5.5), Thermoanaerobacterium sp. related organisms under thermophilic condition (initial pH 7), and Thermoanaerobacterium thermosaccharolyticum related organisms under thermophilic condition (initial pH 5.5). Results from this study clearly indicated that the long-term effects of inoculum pretreatments on hydrogen production, methanogenesis, homoacetogenesis and dominant bacteria were dependent on fermentation temperature and pH.     

Nonlinearity in the Growth of Bacterial Colonies: Conditions and Causes

The universally recognized kinetic model of colony growth, introduced by Pirt, predicts a linear increase of colony size. The linearity follows from the assumption that the colony expands through the growth of only such cells that are located immediately behind the moving colony front, in the so-called peripheral zone of constant width and density. In this work, Pirt's model was tested on two bacteria—Alcaligenes sp. and Pseudomonas fluorescens—having markedly distinct cultural properties and grown on an agarized medium with pyruvate. The colony size dynamics was followed for different densities of the inoculum, ranging from a single cell to a microdroplet of bacterial suspension (10⁵–10⁶ cells), and for different depths of the agar layer, determining the amount of available substrate. A linear growth mode was observed only with P. fluorescens and only in the case of growth from a microdroplet. When originating from a single cell, colonies of both organisms displayed nonlinear growth with a distinct peak of K _r (the rate of colony radius increase) occurring after 2–3 days of growth. The growth of P. fluorescens colonies showed virtually no dependence on the depth of the agarized medium, whereas the rate of colony size increase of Alcaligenes sp. turned out to be directly related to the medium layer thickness. The departure from linearity is consistently explained by a new kinetic scheme stipulating a possible contribution to the colony growth not only of peripheral cells but also (much more distinct in Alcaligenes) of cells at the colony center. The colony growth dynamics is determined not only by the concentration of the limiting substrate but also by the amount of autoinhibitor, the synthesis of which is governed by the age of cells. The distinctions of growth from a single cell and microdroplet could also originate as a result of dissociation into the R- and S-forms and competition between the corresponding subpopulations for oxygen and the common substrate.     

Forest reclamation of fly ash deposit: a field study on appraisal of mycorrhizal inoculation

An extensive field trial was established on a fly ash deposit (1) to evaluate whether the inoculation with arbuscular mycorrhizal fungi (AMF) and/or ectomycorrhizal fungi (EcMF) improves growth and survival of 13 planted tree species and (2) to trace the inoculated mycorrhizal fungi in tree roots after one growing season. Molecular methods were applied to characterize AMF and EcMF entering the studied system (inocula, native soil, and roots of nursery seedlings). Biometric parameters and mortality of the trees were recorded and the presence of AMF and EcMF in sampled trees was determined both microscopically and genetically. Mycorrhizal inoculation did not improve survival or growth of any tree species. Most AMF‐host and all EcMF‐host seedlings were highly precolonized already from the nursery. An abundant and diverse AMF community was also found in the field soil. The AMF inoculum taxa partially overlapped with AMF in the native soil and in the precolonized roots. After one season, the only two inoculum‐unique AMF taxa were detected in host species non‐precolonized or only partially precolonized from the nursery. The components of EcMF inoculum were not detected in any sampled tree. After the season, the ectomycorrhizal hosts maintained most of their original EcMF taxa gathered in nursery, some tree species were additionally colonized by EcMF probably originating from the soil. Our results show considerable self‐restoration potential of nature on the target site. Mycorrhizal inoculation thus did not bring any conclusive advantage to the planted trees and seems superfluous for reclamation practice on the fly ash deposit.     

一株高效苯酚降解真菌的分离鉴定及其菌剂的制备

【背景】含酚废水是普遍存在的有毒、难降解的有机污染物之一,生物法处理含酚废水因成本低、无二次污染而具有广阔的应用前景。可降解苯酚的微生物中,真菌比细菌对恶劣环境的适应性更好。针对液态菌液保存时间较短和运输困难的瓶颈,制备固体菌剂可以提高菌体存活率和储藏稳定性。【目的】筛选一株能够高效降解苯酚的真菌,优化其降酚性能并选择合适的载体制备菌剂。【方法】通过逐级驯化和纯化分离降酚菌,筛选得到降酚性能较强的真菌并通过ITS r DNA基因测序进行种属鉴定,通过参数优化进一步提高菌株降解苯酚的性能;以不同材料为载体制备菌剂,通过稀释平板计数法和苯酚降解实验探究菌剂在不同温度下的保存效果。【结果】分离筛选得到一株高效降解苯酚真菌QWD1,通过鉴定证明其属于Magnusiomyces capitatus,其最适降解条件:(NH_4)_2SO_4为氮源,接种量为15%,pH为7.0,温度为35°C,氮源浓度为14 mmol/L。在此条件下,28 d内对1 600 mg/L苯酚去除率可以达到97.15%;制备菌剂最合适载体为谷糠,适宜保存温度为4°C,保存时间可达到90 d甚至更长,活菌数高达2.5×10~8 CFU/g左右,降解苯酚效果良好。【结论】筛选得到了一株高效降解苯酚真菌,优化其降解性能并将其制备成菌剂,为处理含酚废水提供了新菌种和理论支持。