Soil Saprophytic Fungi Research Articles

Soil saprophytic fungi could be used as an important ecological indicator for land management in desert steppe

Soil microbes are among the most complex and diverse communities on Earth, actively participating in biogeochemical cycles while responding positively to environmental changes. Saprophytic fungi are important factors in soil carbon cycle, and the response and driving factors in grassland to forestland and grassland to farmland conversion in desert steppe are still poorly understood. Therefore, we analyzed the soil microbial community structure and saprophytic fungal communities in grasslands, shrub lands, and farmlands in typical desert grassland areas of northwest China. It was found that the cultivation of desert steppe plants/crops increased the proportion of silt in soil aggregates while decreasing soil salinity and increasing soil total carbon, nitrogen, and organic matter content. Proteobacteria, Actinobacteriota and Ascomycota were the dominant phyla in desert steppe soils, with Proteobacteria, Gemmatimonadota and Mucoromycota were more responsive to soil environment changes. The co-occurrence network relationship further characterized the process of niche sharing/competition between bacteria and fungi. The complexity of the co-occurrence network was deepened by land use, and fungi occupied more of the niche in shrub planting than in desert steppe and maize planting. Network relationships further characterized the process of niche sharing/competition between bacteria and fungi, and land use deepened the complexity of the co-occurrence network, with soil fungi occupying more ecological niches in shrub cultivation than in grassland and maize cultivation. In addition, saprophytic fungi are the main functional fungi in bacterial-fungal co-occurrence networks and are influenced by soil properties. Random forest analysis further explained the importance of saprophytic fungi in response to environmental changes in desert steppes. The enrichment of soil saprophytic fungi had an obvious correlation with soil aggregate stability, soil physical properties, and soil nutrients, especially in the background of shrub forestation in desert steppes. This study further highlights afforestation as one of the ways to benefit land management in desert steppes, while emphasizing the importance of saprophytic fungi as ecosystem indicators.

The distribution of soil fungal communities along an altitudinal gradient in an alpine meadow

Altitude can drive the distribution of living organisms through effects on both soil properties and plant-fungi interactions. We examined how altitude influenced soil fungal communities (including three ecological groups), directly and indirectly through variation in soil properties and/or plant communities, by sampling along an altitudinal gradient from 1300 to 4200 m a.s.l. in an alpine meadow in Western China. We found that soil properties ( r = 0.401; P = 0.001) and plant communities ( r = 0.332; P = 0.001) significantly affected soil fungal community composition. Soil nitrogen content, altitude and nitrate nitrogen content were the best predictors of saprophytic, symbiotic and biotrophic fungi, respectively. Altitude increased the relative abundance (standard coefficient = 0.385) and richness (standard coefficient = 0.689) of soil saprophytic fungi by promoting soil nitrogen content (standard coefficient = 0.574). Altitude directly increased soil symbiotic fungi (standard coefficient = 0.811), while nitrate nitrogen content promoted the richness and abundance of plant fungal pathogens. Our results shed light on drivers of soil fungi community composition and the distribution of different ecological groups along an altitudinal gradient in an alpine meadow.

Soil functional responses to drought under range-expanding and native plant communities.

Current climate warming enables plant species and soil organisms to expand their range to higher latitudes and altitudes. At the same time, climate change increases the incidence of extreme weather events such as drought. While it is expected that plants and soil organisms originating from the south are better able to cope with drought, little is known about the consequences of their range shifts on soil functioning under drought events.Here, we test how range‐expanding plant species and soil communities may influence soil functioning under drought. We performed a full‐factorial outdoor mesocosm experiment with plant communities of range expanders or related natives, with soil inocula from the novel or the original range, with or without summer drought. We measured litter decomposition, carbon mineralization and enzyme activities, substrate‐induced respiration and the relative abundance of soil saprophytic fungi immediately after drought and at 6 and 12 weeks after rewetting.Drought decreased all soil functions regardless of plant and soil origin except one; soil respiration was less reduced in soils of range‐expanding plant communities, suggesting stronger resistance to drought. After rewetting, soil functioning responses depended on plant and soil origin. Soils of native plant communities with a history of drought had more litter mass loss and higher relative abundance of saprophytic fungi than soils without drought and soils of range expanders. Functions of soil from range expanders recovered in a more conservative manner than soils of natives, as litter mass loss did not exceed the control rates. At the end of the experiment, after rewetting, most soil functions in mesocosms with drought history did not differ anymore from the control.We conclude that functional consequences of range‐expanding plants and soil biota may interact with effects of drought and that these effects are most prominent during the first weeks after rewetting of the soil. A free http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.13453/suppinfo can be found within the Supporting Information of this article.

Effect of mixing soil saprophytic fungi with organic residues on the response of Solanum lycopersicum to arbuscular mycorrhizal fungi

AbstractThe effect of the dual inoculation with arbuscular mycorrhizal (AM) and saprophytic fungi and a combination of wheat straw and sewage sludge residues were studied by determining their effect on dry weight of tomato and on chemical and biochemical properties of soil. Incubation of organic residue (sewage sludge combined with wheat straw) with saprophytic fungi and plant inoculation with mycorrhizal fungi was essential to study plant growth promotion. Soil application of organic residues increased the dry weight of tomato inoculated with Rhizophagus irregularis. The greatest shoot dry mass was obtained when the organic residues were incubated with Trichoderma harzianum and applied to AM plants. However, the greatest percentage of root length colonized with AM in the presence of the organic residues was obtained with inoculation with Coriolopsis rigida. The relative chlorophyll was greatest in mycorrhizal plants regardless of the presence of either saprophytic fungus. The presence of the saprophytic fungi increased soil pH as the incubation time increased. Soil nitrogen and phosphorus contents and acid phosphatase were stimulated by the addition of organic residues, and contents of N and P. Total N and P content in soil increased when the organic residue was incubated with saprobe fungi, but this effect decreased as the incubation period of the residue with saprobe fungi increased. The same trend was observed for soil β‐glucosidase and fluorescein diacetate activities. The application of organic residues in the presence of AM and saprophytic fungi seems to be an interesting option as a biofertilizer to improve plant growth and biochemical parameters of soils.

Exploitation of for the Heterologous Production of Cellulases and Hemicellulases

Filamentous fungi of the group are native soil saprophytic fungi. Industrial strains of this group have been extensively used for the production of plant degrading enzymes for the food and beverage, animal feed and paper-and-pulp industries. Recombinant DNA technology allows for the overproduction of these enzymes in copious amounts. The advantages and limitations of A. niger as recombinant host for enzyme production are briefly discussed. Specific attention is devoted to the overproduction of several cellulases and hemicellulases to high homogeneity in the protease-deficient strain A. niger D15. The size, temperature and pH optima of the heterologous enzymes were shown to be similar to that of their natively produced counter parts. The optimization of enzyme production in dilute sugar cane molasses, using a recombinant strain producing the xylanase II of Trichoderma reesei as example, was also demonstrated.

Decomposition rate of organic substrates in relation to the species diversity of soil saprophytic fungi.

Despite the great interest concerning the relationship between species diversity and ecosystem functioning, there is virtually no knowledge as to how the diversity of decomposer microbes influences the decomposition rate of soil organic matter. We established a microcosm study in which the number of soil fungi was investigated in relation to the system's ability to (i) degrade raw coniferous forest humus, and (ii) use resources that were either added to the systems or released into the soils after a disturbance (drought). With the exception of the most diverse treatment, in each of the six replicates of each of the six diversity treatments (1, 3, 6, 12, 24 or 43 taxa), fungal taxa were randomly chosen from a pool of 43 commonly isolated fungal species of raw humus. Two months after initiation of the study CO2 production increased as fungal diversity increased, but in the species-poor end of the diversity gradient only. Addition of various energy resources to the microcosms generally increased the level of soil respiration but did not affect the shape of the diversity-CO2-production curve. Rewetting the soil after severe drought resulted in a rapid flush of CO2, particularly in the most diverse communities. The biomass of the fungi in the non-disturbed soils, and soil NH4-N concentration and soil pH in both disturbed and non-disturbed systems were slightly but significantly higher in the diverse than in the simple systems. Fungal species richness had no influence on the organic matter content of the humus at the end of the experiment. The results suggest that the functional efficiency of fungal communities can increase with the number of fungal taxa. This diversity effect was, however, significant at the species-poor end of the diversity gradient only, which implies considerable functional equivalency (redundancy) among the decomposer fungi.

Tracking the fates of exotic and local VA mycorrhizal fungi: methods and patterns

Vesicular-arbuscular (VA) mycorrhizal fungi are an abundant component of the soil biota in most terrestrial ecosystems, and represent a distinct trophic group (biotrophic) from most of the rest of the soil microbial biomass (saprotrophic). Vesicular-arbuscular mycorrhizal fungi are comprised of a wide diversity of species and are often transplanted between habitats to increase plant growth. We tested the use of polyclonal antibodies on field and pot samples that might allow us both to differentiate VA mycorrhizal fungi from soil saprophytic fungi, and between introduced and native VA mycorrhizal fungi. The immunofluorescent antibody technique is advantageous in that it is easy and relatively inexpensive. In addition, fluorescent antibodies allowed for rapid differentiation of our introduced VA mycorrhizal fungus from indigenous saprophytic extramatrical hyphae. However, the specificity is not high against other VA mycorrhizal hyphae of similar taxonomic status, but is applicable clearly when the exotic VA mycorrhizal fungus is a different genus from the local fungi. This ability to differentiate an introduced fungus by its positively fluorescing external hyphae allows the researcher to undertake survival and developmental studies that are not limited by the constraints of infrequent or patchy sporulation. Using this technique, we determined that exotic VA mycorrhizal fungi can survive for up to 2 years even with competition from the local endophytes, and that the vertical placement of the inoculum can affect the survival of the exotic fungi at our sagebrush steppe research site in south-western Wyoming.

THE BIOLOGY OF MYCORRHIZA IN THE ERICACEAE

SummaryYoung mycorrhizal plants of Vaccinium macrocarpon could utilize amino acids as a nitrogen source as readily as ammonium whereas aseptically grown plants and plants inoculated with common soil saprophytic fungi were unable to utilize the organic nitrogen compounds. Seedlings of Festuca ovina grown as controls in the sterile condition and in the presence of the ericaceous endophyte also failed to utilize the amino compounds. The capacity of the ericaceous plant to exploit these compounds is therefore dependent upon mycorrhizal infection. In contrast to cultures of Marasmius oreades, the endophyte failed to grow on complex nitrogenous humic and fulvic acids extracted from soils under ericaceous plants. The capacity to utilize simple organic nitrogen compounds could be of importance for mycorrhizal ericaceous plants in mor‐humus soils which are characterized by slow rates of nitrogen mineralization.