Role Of Soil Fungi Research Articles

Microbial pathways account for the pH effect on soil N2O production

Clarifying the responses of different N2O production pathways to pH change is helpful to better understand the effect of pH on N2O emission from soils. A15N tracing study was carried out on subtropical forest (SF) and cropland (SC) soil in 30-day pH manipulation treatments to quantify the effect of pH on autotrophic nitrification, heterotrophic nitrification and denitrification-derived N2O. Gene abundances of autotrophic nitrification (AOA-amoA, AOB-amoA) and denitrification (nirK, nirS, nosZ) -related N2O production were determined to identify the microbial mechanism behind the pH effect on N2O production. The results showed that the total N2O production rate (N2Ot) of the SF soil was 4.56 and 4.86 μg N kg−1 day−1 at pH 3.5 and 4.5, respectively, which was significantly higher than the other treatments. Similarly, the highest N2Ot of the SC soil was also observed in pH 3.5 treatment (7.15 μg N kg−1 day−1). Both N2O production rate via denitrification (N2Od) and heterotrophic nitrification (N2Oh) markedly increased, while the N2O production rate via autotrophic nitrification (N2Oa) markedly decreased by decreasing pH in both the SF and SC soil. Thus, denitrification and heterotrophic nitrification were responsible for the high N2O production under strongly acidic conditions. The abundance of nosZ gene was significantly and negatively correlated with N2Od (P < 0.05), and the abundance of AOB-amoA was significantly and positively correlated with N2Oa (P < 0.01). The results of the structural equation modeling (SEM) analysis revealed that soil pH generated a more direct effect on the denitrifying and ammonia-oxidizing gene abundance, in turn, affected N2Od and N2Oa, respectively. In addition, soil pH exerted a significant effect on both the bacterial 16S rRNA and fungal ITS rDNA gene abundance (P < 0.05). However, the role of soil fungi and bacteria on N2Oh could not be determined in this study.

The Role of Soil Fungi in K+ Plant Nutrition

K+ is an essential cation and the most abundant in plant cells. After N, its corresponding element, K, is the nutrient required in the largest amounts by plants. Despite the numerous roles of K in crop production, improvements in the uptake and efficiency of use of K have not been major focuses in conventional or transgenic breeding studies in the past. In research on the mineral nutrition of plants in general, and K in particular, this nutrient has been shown to be essential to soil-dwelling-microorganisms (fungi, bacteria, protozoa, nematodes, etc.) that form mutualistic associations and that can influence the availability of mineral nutrients for plants. Therefore, this article aims to provide an overview of the role of soil microorganisms in supplying K+ to plants, considering both the potassium-solubilizing microorganisms and the potassium-facilitating microorganisms that are in close contact with the roots of plants. These microorganisms can influence the active transporter-mediated transfer of K+. Regarding the latter group of microorganisms, special focus is placed on the role of endophytic fungus. This review also includes a discussion on productivity through sustainable agriculture.

The Characterization of the Selected Trees Damaged During Severe Weather Episode on the Mountain Avala (Serbia) Using IR Thermography, ICP-OES, and Microbiological Analysis

Selected plants of white fir and lime, damaged during severe weather episode on the mountain Avala (Serbia) in summer 2014, were analyzed and characterized (including their spatial soil samples) by inductively coupled plasma optical emission spectroscopy (ICP-OES), infrared (IR) thermography, and microbiological method such as enumeration of cultivable microorganisms. The results obtained from chemical and microbiological analyses provided valuable information on possible biotic and abiotic stressors such as soil fungi and heavy metals, which could affect the health status of trees, while IR thermography visualized this status in a very specific and effective way. The results of ICP-OES analysis clearly showed that the investigated heavy metals (Cu, Zn, Pb, As, Cd, and Ni) were less likely crucial factors responsible for ruined health status of damaged trees. The role of soil fungi was not clear, since the results of microbiological analysis only provided evidence that their amounts in all investigated soil samples were within normal ranges as well as that their amounts in the corresponding samples of the uprooted trees were much greater than in the case of snapped trees. Therefore, further molecular characterization of microorganisms should be performed to identify if pathogenic species are present and clarify their role. Nevertheless, all used methods, especially IR thermal imaging as a totally non-invasive, fast and very comfortable technique, can be recommended as very useful in preventive screening of the trees’ health status and for early detection of tissue decay that usually hamper trees survival or resistance to extreme weather events.

Fungal and Bacterial Diversity Isolated from Aquilaria malaccensis Tree and Soil, Induces Agarospirol Formation within 3 Months after Artificial Infection.

Aquilaria malaccensis Lam, commonly known as Agarwood, is a highly valuable species used in production of agar oil from its infected wood, which is utilized in pharmaceutical and perfumery industry. Agar oil formation in agarwood takes years through the natural process which is induced by natural or artificial injury or microbial infection. The role of soil fungi and bacteria in artificial induction is still an unexplored area. In the present study, we isolated the fungal and bacterial community residing inside the stem of A. malaccensis tree and circumventing soil, samples collected from 21 different sites of the north-eastern state Assam of India and explored their potential in induction of Agarospirol (2-(6,10-Dimethylspiro[4,5]dec-6-en-2-yl)-2-propanol) production by artificially infecting the trees with these microorganisms. A total 340 fungi and 131 bacteria were isolated from 50 stem samples, and 188 fungi and 148 bacteria were isolated from 50 soil samples. Highest Shannon (H′ = 2.43) and Fisher (α = 5.57) diversity index was observed in the stem isolates. The dominant fungal genus was Trichoderma in stem with Pi value of 0.18; while in soil, Aspergillus showed dominance with Pi value 0.73. In bacteria, Bacillus genera showed dominance in both stem and soil samples with Pi = 0.62 and 0.51, respectively. Forty fungal and bacterial isolates were used to assess their potential to induce formation of agarwood in A. malaccensis by artificial infection method. Gas chromatography mass spectroscopy (GC-MS) analysis confirmed development of Agarwood by the presence of Agarospirol compound in samples collected after 3 months of the artificial infection. Only 31% of bacterial and 23% of fungal isolates showed their ability in production of Agarospirol by artificial infection method. Bacteria Pantoea dispersa and fungi Penicillium polonicum showed the highest production in comparison to other isolates.

The role of soil fungi and bacteria in plant litter decomposition and macroaggregate formation determined using phospholipid fatty acids

Although microbial-derived carbon (C) inputs to soil are increasingly acknowledged as an important source of soil organic matter (SOM), the contribution of different microbial compounds to soil C transformation and their role in aggregation remain poorly understood. This study assessed the contribution of soil fungi and bacteria to the decomposition of maize residues by means of extracted phospholipid fatty acids (PLFAs) and 13C in specific PLFAs and investigated the importance of soil fungi in the formation of macroaggregates. Sieved soil (<250μm) was incubated for 28 days with and without addition of maize residues and fungicide. Our results show a significant relation between the amount of fungal PLFA 18:2ω6 and the amount of macroaggregates. Further, the amount of macroaggregates was higher in the treatment with the higher amount of maize-derived C in fungal PLFA, suggesting that fungal activity is important for macroaggregate formation. Based on an increased incorporation of maize-derived C into actinomycetes in fungicide treatments, we suggest that actinomycetes may take over the role of soil fungi in the decomposition of SOM. Our study underpins the important role of soil fungi in the decomposition of organic matter and structure formation in the soil, and shows that during inhibition of soil fungi other soil microorganisms are promoted and adopt their function in the soil food web.

Biodegradation of lindane pesticide by non white- rots soil fungus Fusarium sp.

Lindane or γ- hexachlorocyclohexane (γ-HCH) is a chlorinated pesticide and its toxic effects on biota necessitate its removal. Microbial degradation is an important process for pesticide bioremediation and the role of soil fungi in recycling of organic matter prompted us to study the biodegradation of lindane using fungi. This study aims at enrichment, isolation and screening of soil fungi capable of metabolizing lindane. Two Fusarium species (F. poae and F. solani) isolated from the pesticide contaminated soil showed better growth on the plates supplemented with lindane as a sole carbon source, when compared with the growth performance of other fungal isolates from the same contaminated soil. However, ANOVA revealed a significant difference in fungal biomass production in both F. poae (F = 22.02; N = 15; P < 0.001) and F. solani (F = 268.75; N = 15; P < 0.001) across different lindane concentrations (0–600 μg ml−1). Growth of both Fusarium sp. was maximum at a lindane concentration of 100 μg ml−1, while minimum at 600 μg ml−1 concentrations. Results on the time dependent release of chlorine by the Fusarium strains in the presence of various concentration of lindane showed the highest mineralization of the pesticide on 10th day of incubation. Time dependent variations in the release of chlorine from 1st to 10th day by both the selected fungal strains were found to be statistically significant. A significant positive relationship exists between fungal biomass increase and chlorine release existed for both F. solani (R² = 0.960) and F. poae (R² = 0.628). The results of gas chromatograph analysis of γ- HCH confirmed the biodegradation and utilization of γ- HCH by F. poae and F. solani. The data on lindane degradation by the two fungal strains demonstrated that the biodegradation of lindane by F. solani (59.4%) was slightly higher than that by the F. poae (56.7%).

Biodegradation of organochlorine pesticide, endosulfan, by a fungal soil isolate, Aspergillus niger

Abstract Endosulfan is a chlorinated pesticide widely used in India for the protection of cotton, tea, sugarcane and vegetables. The persistence of endosulfan in environment and toxic effects on biota necessitate its removal. The role of soil fungi in recycling organic matter prompted us to attempt biodegradation of endosulfan using fungi. This study aims at enrichment, isolation and screening of fungi capable of metabolizing endosulfan. In all, 16 fungal isolates were obtained by enrichment of soil samples that had seems exposed to endosulfan before. Isolates were screened by a gradient plate assay, and results were confirmed by broth assay. On the basis of tolerance to endosulfan, an isolate, identified as Aspergillus niger was selected for further studies. The culture could tolerate 400 mg ml−1 of technical grade endosulfan. Complete disappearance of endosulfan was seen on 12 days of incubation. Evolution of carbon dioxide during endosulfan metabolism has indicated the complete mineralization of endosulfan. Change in pH of culture broth to acidic range supported the biological transformation. Thin layer chromography (TLC) analyses revealed the formation of various intermediates of endosulfan metabolism including endosulfan diol, endosulfan sulfate, and an unidentified metabolite. The toxic intermediate, endosulfan sulfate, was also metabolized, further resulting in complete mineralization of endosulfan. Direct desulfurization of endosulfan sulfate or a novel pathway could be the mechanism of endosulfan and endosulfan sulfate degradation in Aspergillus niger. The fungal strain isolated by us could prove valuable for bioremediation of endosulfan contaminated soils and waters.

Temperate Eucalypt Woodlands in Australia: Biology, Conservation, Management and Restoration

TEMPERATE Eucalypt Woodlands in Australia provides a comprehensive account of the biology, conservation and management and rehabilitation of one of the most important broad-vegetation types in Australia. The book is divided into four sections, the distribution and status of woodlands, threats, processes and management, regeneration and repair and finally socio-economic issues. Chapters cover a wide range of issues including tree decline, the role of soil fungi, the impacts and opportunities of fuel wood extraction and the attitude of landholders to environmental issues. The characteristics and current status of the temperate woodlands in each state are separately covered in individual chapters. Contributions are included from many different authors and from sources across Australia and for the first time students, researchers or the general public can access information on this fascinating subject. Extensive bibliographies attached to each chapter will enable the reader to pursue topics in greater detail.

Rhizosphere and root-infecting fungi and the design of ecological field experiments.

As part of a wider study into the role of soil fungi in the ecology of the winter annual grass, Vulpia ciliata ssp. ambigua (Le Gall) Stace & Auquier, we applied the fungicides benomyl and prochloraz to three natural populations of the grass growing in East anglia, United Kingdom. The rhizosphere and rootinfecting fungi associated with the three populations were analysed each month between February and May 1992 when plants set seed. There were marked differences between the fungal floras associated with each of the three populations of V. ciliata, despite the fact that associated plant species and soil nutrient status were broadly similar between sites. This was attributed to wide differences in soil pH between the three populations. Prochloraz did not affect fungal abundance, but benomyl decreased the isolation frequencies of Fusarium oxysporum from roots and the frequencies of Penicillium and Trichoderma spp. isolated from rhizosphere soil, and increased the frequency of isolation of Mucor hiemalis from the rhizosphere of V. ciliata. There were also significant increases in the isolation frequencies of F. oxysporum from roots and M. hiemalis, Trichoderma spp. and Phoma fimeti from the rhizosphere of V. ciliata as plants matured. The significance of these results for the design of ecological field experiments are discussed in light of a previous study which has shown that asymptomatic root-infecting fungi can affect plant fecundity and hence abundance in natural populations of V. ciliata. We propose that differences in microbial communities between sites, controlled in part by soil chemistry, are a major factor determining plant performance under field conditions.

Potential role of fungi and bacteria in Chinese fir replant soil

The role of soil fungi and Bacillus in the Chinese fir (Cunninghamia lanceolata) replant problem was investigated. Several pathogenic fungi isolated were more abundant in replant than in non-replant woodland soil, but the species composition of soil bacteria showed no significant differences. Fumigation of replant soils with methyl bromide significantly increased the growth of Chinese fir compared with nonfumigated soils. Inoculation of steam-sterilized soil with the pathogenic fungi caused significant reduction of growth of Chinese fir seedlings, while amendment with bacteria from the soil had no effect on seedling growth. However, the combination of pathogenic fungi and bacteria greatly reduced plant growth and increased root rot compared with pathogenic fungi or bacteria alone. It is suggested that fungi alone or in combination with bacteria may be important biotic factors in the Chinese fir replant problem. Key words: fungi, bacteria, Chinese fir, replanted soil, seedling growth.

Citrus replant problem in Iraq I. Possible role of soil fungi and nematodes

The role of soil fungi and nematodes in citrus replant problems was investigated. Several pathogenic and non-pathogenic fungi and the nematodeTylenchulus semipenetrans were isolated in about equal abundance from soils which displayed or did not display replant problems. However, in almost all trees showing evidence of decline, infection by the fungusPhytophthora citrophthora had advanced through the roots until it had reached the tree crown. Fumigation of old citrus soil with methyl bromide greatly increased the growth of sour organe. The application of Nemacure, Benomyl and Ridomil 5G confirmed the important role of pathogenic and non-pathogenic fungi and nematodes in the citrus replant problem. Inoculation of methyl bromide-treated soil with the pathogenic and non-pathogenic fungi separately or in combination further confirmed the previous experiments and also revealed an important role ofP. citrophthora andFusarium solani when replanting citrus in old citrus orchards.

Use of cotton strips to relate fungal community structure to cellulose decomposition rates in the field

Studies on the ecology of soil fungi have traditionally been concerned with the distribution of taxa in the soil, and the influence of the environment on community structure and composition. Relatively little emphasis has been placed on the role of the fungal community and the effects of community composition on decomposition processes, even though it is recognized that the decomposition of natural compounds is a major function of the fungal community. One approach to defining the role of soil fungi in the decomposition process is to take an inventory of the fungi in the soil, evaluate their enzymatic capacity under laboratory conditions and then use these data to make inferences about the role of the community in decomposition of natural substrates, as has been done by Flanagan and Scarborough (1974) and Gochenaur (1984). Using this approach, and comparing soils, Flanagan (198 1) concluded that “it appears that taxonomic differences in fungal communities between ecosystems do not significantly influence the decay rate of plant remains between sites. The biomass of fungi is related to quantity and quality of organic matter, and the decay rate of a given organic matter is controlled primarily by climates”. Although such studies provide useful information, they suffer from the fact that soil fungi are being tested under artificial conditions for their potential for decomposing specific substrates. To interpret the role of fungal community structure on actual decomposition rates, it would be better to examine fungi actually colonizing particular substrates, from the soil, and to monitor simultaneously the amount of decomposition that is taking place. An opportunity to do this arose as part of an ongoing study on the effects of amendments on the decomposition of cotton (cellulose) strips, buried in a Scottish moorland soil. Cotton strips of uniform weave, 1Ocm wide by 30 cm, were prepared (Latter and Howson, 1977) and inserted into an acid (pH 4.345) Scottish moorland soil near Banchory (Grid Ref. No. 637903). The general area of the study has been described in detail by Miles (1973). The top segments of the strips were placed in the old litter/F horizon, the side segments in the variable O/H/Ah horizon, and the bottom segments in the E/Es horizons (nomenclature according to Hodgson, 1974) using the method of French and Howson (1982). On 25 August 1981, five replicate strips were placed randomly in each of three plots that had been amended as follows: (i) N aDDlied as NH.NO, at a rate of 40 am-‘: (ii) P applied as KH;FCJ, at 60 gm-*, (iii) Ca applied& Ca;cb; at 100 g m-*. A further 5 strips were distributed between three plots treated with a 1: 1 mixture of glucose and potato starch: two in a plot treated at 4 g m-*, one in a plot treated at 16gm-* and the remaining two in a plot treated at 40 g m-*. Data from these three plots were combined as a single “carbohydrate” treatment. All amendments had been applied on three occasions during 1979; on 19 September, 15 October and 30 October. Five strips were also inserted in unamended control plots. The strips were removed on 8 December 198 1 and the side segments were cut, frayed and tested for tensile strength (Latter and Howson, 1977). Unburied control strips were simultaneously tested for tensile strength and the percent tensile strength loss for test strips was calculated as follows:

Biological and Mechanical Role of Soil Fungi

Biological and Mechanical Role of Soil Fungi