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1.
《Geoderma》2005,124(3-4):349-361
We tested termite mound materials belonging to different feeding groups: Cubitermes (soil-feeder), Trinervitermes (grass-feeder) and Macrotermes (litter-feeder), as natural microbial inoculum to promote plant growth and increase nutrient supplies from soil organic matter and inorganic amendments (rock phosphate), through their effects on soil microorganisms (functional diversity of soil microflora, arbuscular mycorrhizal fungi, rhizobia, fluorescent pseudomonads, actinomycetes and saprophytic fungi). Experiments were made in a pot experiment with Acacia seyal, a leguminous tree abundant in West Africa, with a sandy soil amended or not with rock phosphate. Results indicated a stimulation of plant growth with Cubitermes and Trinervitermes mound powder (plant height and shoot biomass), similar to what was obtained with rock phosphate alone. Leaf content in N was also increased in the termite treatments (except in Macrotermes soil), whereas mycorrhizal colonization was inhibited as compared to the control. The development of saprophytic fungi was significantly higher in the soils amended with rock phosphate and this effect was hypothesized to be related to the production of large quantities of oxalic acid by fungal populations. The fluorescent pseudomonad populations notably increased in the soils dually amended with mound powders and rock phosphate, and this could be due to the fact that some species of this bacterial group are able to dissolve rock phosphate. The organic and inorganic amendments decreased the soil catabolic evenness in all the mound powder treatments. Among the mound materials tested, Cubitermes mound powder had the most promising effect, especially on SIR response to oxalate. It is concluded that soils amended both with rock phosphate and Cubitermes mound soil could promote the development of microbial communities, which could help to metabolize this compound and consequently enhance plant growth.  相似文献   

2.
Interactions between Rhizobium and soil rhizosphere microorganisms on agar were examined using the giant-colony and the streak methods. The interactions between microorganisms often varied when the test method was changed. Soil and rhizosphere microorganisms produced greater stimulation or inhibition of Rhizobium when the Rhizobium was suspended within the agar. Giantcolonies of Rhizobium were limited in their effects upon soil microorganisms. When microorganisms were streaked at right angles to each other, interaction occurred only between those streaked 3 days apart and not between those streaked on the same day. Inhibition effects were very pronounced and stimulation was less evident with the streak method. Toxin production was implicated with selfinhibition of rhizobia and soil microorganisms. Stimulatory, inhibitory and lytic activity of soil microorganisms were confirmed with sterile broth extracts of 2 and 5 day old cultures. pH changes in the media as a result of microbial activity were not considered responsible for the interactions observed.  相似文献   

3.
根际微生物的代谢作用, 直接促进或抑制根的营养吸收和生长, 也影响根际土壤中的物质转化, 雷公藤根系发达且多与其他树种混交栽培, 其根际微生物活性对雷公藤的生长和土壤肥力均有不可忽视的影响。以福建省泰宁县3 种不同栽培模式雷公藤林(野生雷公藤林、杉木雷公藤混交林、厚朴雷公藤混交林)为研究对象, 通过稀释平板法测定3 种不同雷公藤林分根际土壤和非根际土壤中细菌、真菌、放线菌的数量。结果表明: 根际土的微生物数量大于非根际土的微生物数量; 3 种林分, 无论是在根际土壤中, 还是在非根际土壤中, 均表现为细菌数量＞放线菌数量＞真菌数量; 根际微生物(R)比非根际微生物(S)更活跃, 3 种林分的3 大类微生物的R/S 数量比值均大于1; 3 种林分的微生物活性表现为厚朴雷公藤混交林＞杉木雷公藤混交林＞野生雷公藤林, 表明混交方式可促进雷公藤根际微生物活性。  相似文献   

4.
Plant growth promoting microorganisms (PGPM) and biological control agents (BCA) are shown to possess secondary beneficial effects that would increase their usefulness as bio-inoculants, regardless of the need for their primary function. Indeed, PGPM, such as Rhizobium and Glomus spp., can promote plant growth and productivity (primary effect) but have now been shown to also play a role in reducing disease (secondary effect). Conversely, BCA, such as Trichoderma and Pseudomonas spp., can control disease (primary effect) but have recently demonstrated stimulation of plant growth (secondary effect) in the absence of a pathogen. Further work shedding light onto the precise mode of action and ecophysiology of these microorganisms would assist with their timely and appropriate use and potentially unleash their full promise as beneficial rhizosphere bio-inoculants for improved growth and health of plants. The potential increased use of these microorganisms afforded by their multifaceted beneficial effects may further help in reducing problems associated with the use of synthetic chemicals in agriculture.  相似文献   

5.
Sugar beet waste has potential value as a soil amendment and this work studied whether fermentation of the waste by Aspergillus niger would influence the growth and P uptake of arbuscular mycorrhizal (AM) fungi. Plants were grown in compartmentalised growth units, each with a root compartment (RC) and two lateral root-free compartments (RFC). One RFC contained untreated soil while the other RFC contained soil, which was uniformly mixed with sugar beet waste, either untreated (SB) or degraded by A. niger (ASB) in a rock phosphate (RP)-supplied medium. The soil in each pair of RFC was labelled with 33P and 32P in order to measure P uptake by the AM fungal mycelium, of which length density was also measured. Whole cell fatty acid (WCFA) signatures were used as biomarkers of the AM fungal mycelium and other soil microorganisms. The amount of biomarkers of saprotrophic fungi and both Gram-positive and Gram-negative bacteria was higher in SB than in ASB treatments. Whilst ASB increased growth and activity of AM mycelium, SB had the opposite effect. Moreover, shoot P content was increased by the addition of ASB, and by inoculation with AM fungi. Modification of soil microbial structure and production of exudates by A. niger, as a consequence of fermentation process of sugar beet waste, could possibly explain the increase of AM growth in ASB treatments. On the other hand, the highest P uptake was a result of the solubilisation of rock phosphate by A. niger during the fermentation.  相似文献   

6.
The influence of the Gumigel bacterial-humus preparation on the biological activity of soils was investigated. The activity was assessed by the respiration intensity of the soil microorganisms, the total number of bacteria, and the structure of the saprotrophic bacterial complex. It was demonstrated that the microorganisms were preserved in the preparation for a long time. As this preparation was kept at 4°C, the number of microorganisms was preserved at a permanent level during no less than half a year. The preparation did not have a significant effect on the biological activity of the unpolluted soil, but it intensified the biological activity in the case of the polluted soil, which was seen from an increase in the number of microorganisms and their respiration intensity.  相似文献   

7.

Purpose

The effect of pollutants in soil microorganisms is an important issue in order to understand their toxic effects in the environment, as well as for developing adequate bioremediation strategies. In this sense, the main objective of this study was to assess the involvement of the indigenous microbiota of an acidic forest Mediterranean soil by artificial pollution with heavy metals, and to detect and isolate resistant microorganisms that could be useful for bioremediation.

Materials and methods

Samples from a previously unpolluted acidic forest soil were amended with Cr(VI), Cd(II) or Pb(II) at total amounts ranging from 0.1 to 5,000 mg?kg?1. These soil microcosms were incubated under controlled laboratory conditions for 28 days. Soluble fractions of metals were determined from aqueous extracts. Both activity and composition of the microbial community were assessed, respectively, by respirometric assays and molecular analysis (polymerase chain reaction denaturing gradient gel electrophoresis). The isolation of metal-resistant microorganisms was attempted by culture plating from microcosms incubated with high concentrations of metals. Isolated strains were tested in cultures with minimal medium to check for their metal resistance and their capacity to reduce the presence of toxic Cr(VI).

Results and discussion

A decrease in the soil respirometric activity and changes in the microbial community composition were detected from 10/100 mg?kg?1 Cr and 1,000 mg?kg?1 Cd and Pb. Presumably resistant bacterial and fungal populations developed in most of these polluted microcosms; however, the microbiota was severely impaired at the highest additions of Cr. Even though Cr was the most damaging metal in soil microcosms, if the soluble fractions of metals are considered instead of their total added amounts, the comparison among their toxic effects suggests a similar potential toxicity of Cr and Pb. Isolated multiresistant microorganisms were related mainly to Actinobacteria, Firmicutes and Ascomycota. Some of them showed the capacity to reduce Cr(VI) concentrations between 54 % and 70 % of the initial value. These strains were affiliated to several species of Streptomyces and Bacillus.

Conclusions

The combination of respirometric assays with molecular methods has been useful to assess the effect of metals on the soil microbial community, which can greatly be explained by their differential bioavailability. Cultivation-dependent and -independent approaches have proved the presence and development of multiresistant microorganisms in a previously unpolluted soil. Due to their properties, some of the isolated strains are potentially useful for soil bioremediation.  相似文献   

8.
Interactions between the biocontrol fungus Clonostachys rosea IK 726 and a tomato/Glomus intraradices BEG87 symbiosis were examined with and without wheat bran, which served as a food base for C. rosea. In soil without wheat bran amendment, inoculation with C. rosea increased plant growth and altered shoot nutrient content resulting in an increase and decrease in P and N content, respectively. Inoculation with G. intraradices had no effect on plant growth, but increased the shoot P content. Dual inoculation with G. intraradices and C. rosea followed the pattern of C. rosea in terms of plant growth and nutrient content. Wheat bran amendment resulted in marked plant growth depressions, which were counteracted by both inoculants and dual inoculation increased plant growth synergistically. Amendment with wheat bran increased the population density of C. rosea and reduced mycorrhizal fungus colonisation of roots. The inoculants were mutually inhibitory, which was shown by a reduction in root colonisation with G. intraradices in treatments with C. rosea and a reduction in colony-forming units (cfu) of C. rosea in treatments with G. intraradices, irrespective of wheat bran amendment. Moreover, both inoculants markedly influenced soil microbial communities examined with biomarker fatty acids. Inoculation with G. intraradices increased most groups of microorganisms irrespective of wheat bran amendment, whereas the influence of C. rosea on other soil microorganisms was affected by wheat bran amendment. Overall, inoculation with C. rosea increased and decreased most groups of microorganisms without and with wheat bran amendment, respectively. In conclusion, despite mutual inhibition between the two inoculants this interaction did not impair their observed plant growth promotion. Both inoculants also markedly influenced other soil microorganisms, which should be further studied in relation to their plant growth-promoting features.  相似文献   

9.
An understanding of the types of interactions that take place between plant pathogens and other microorganisms in the natural environment is crucial in order to identify new potential biocontrol agents. The use of microorganisms labelled with stable isotopes is a potentially useful method for studying direct parasitisation of a given pathogen or assimilation of the pathogen's metabolites by microorganisms. A microorganism labelled with a stable isotope can be monitored in the environment and isotope ratio mass spectrometry can detect whether it is directly parasitised or its metabolites are used by other microorganisms. In this study, we isolated 158 different species of fungi and bacteria from soil and assayed their biocontrol potential against a plant pathogen (Armillaria mellea) by coupling a dual-culture test with mass spectrometry analysis of the 13C isotope in the microorganisms in presence of 13C-labelled A. mellea. The microorganisms affected the pathogen by means of antibiosis phenomena (total or partial inhibition of pathogen growth, alteration of its morphology) and by antagonism, probably resulting from competition for space and nutrients or from mycoparasitism. Isotope ratio mass spectrometry was used to identify direct trophic interactions between microorganisms and the pathogen as in dual cultures as in soil microcosms. Six fungi and one bacterium were found to display the best active trophic behaviour against the pathogenin dual cultures; three microorganisms were discarded due to their plant pathogen potential. Trichoderma harzianum, Pseudomonas fluorescens and Rhodosporidium babjevae were selected to carry out the experiments. T. harzianum inhibited pathogen development (rate of inhibition 80 ± 0.19%) and its δ 13C values increased (244.03 ± 36.70‰) in contact with 13C-labelled A. mellea. Lower levels of antagonism and correspondingly lower assimilation of 13C were detected in P. fluorescens and R. babjevae. Only T. harzianum maintained mycoparasitic activity in the soil microcosm, showing a δ 13C value of 1.97 ± 2.24‰ after one month in co-presence with the labelled pathogen. This study provides support for the use of isotope ratio mass spectrometry as an additional tool in screening for potential biocontrol agents.  相似文献   

10.
Arbuscular mycorrhizal (AM) development in different soil types, and the influence of AM fungal hyphae on their original soil were investigated. Plantago lanceolata, which can grow in soils of a very wide pH range, was grown in two closely related limestone soils and an acid soil from rock habitats. Plants were colonised by the indigenous AM fungal community. The use of compartmented systems allowed us to compare soil with and without mycorrhizal hyphae. Root colonisation of P. lanceolata was markedly higher in the limestone soils (30-60%) than in the acid soil (5-20%), both in the original habitat and in the experimental study. Growth of extraradical AM fungal hyphae was detected in the limestone soils, but not in the acid soil, using the signature fatty acid 16:1ω5 as biomass indicator. Analysis of signature fatty acids demonstrated an increased microbial biomass in the presence of AM fungal hyphae as judged for example from an increased amount of NLFA 16:0 with 30 nmol g−1 in one of the limestone soils. Bacterial activity, but not soil phosphatase activity, was increased by around 25% in the presence of mycorrhizal hyphae in the first harvest of limestone soils. AM fungal hyphae can thus stimulate microorganisms. However, no effect of AM hyphae was observed on the soil pH or organic matter content in the limestone soils and the available P was not depleted.  相似文献   

11.
基于高通量测序技术的燕窝罐头腐败嗜热菌分析   总被引：2，自引：2，他引：0  
为了研究燕窝罐头生产过程微生物结构的变化,同时筛查出造成燕窝罐头安全隐患的嗜热微生物,该研究通过16S rRNA高通量测序技术结合传统培养分离方法研究燕窝生产中燕窝原料、冰糖原料、蒸煮锅糖液、灌装车间毛巾、灌装口糖液、挑毛车间毛巾、汽蒸后燕窝、灌装后产品的微生物组成.Alpha多样性研究结果表明灌装工序是微生物可能显著...  相似文献   

12.
Analysis of published data revealed that there was no correlation between propagule size and longevity among 66 species of microorganisms. The correlation coefficient was —0.204 which was not significantly different from zero at P = 0.05. However, there was an inverse relationship between propagule size and number of propagules produced per unit area of nutrient media among 43 identified species of microorganisms tested. The total volumes (volume x number) of propagules produced per unit area were fairly constant and were not correlated with propagule size. Similar correlations were obtained with propagules produced on diseased fruits by 6 pathogenic fungi. There was a good correlation (r = 0.974) between reproductive capacity and relative abundance in soil among selected microorganisms. It is, therefore, postulated that the higher reproductive capacity of smaller microorganisms, as compared to large microorganisms, is an important factor leading to the inverse size-number relationship among microorganisms in nature.  相似文献   

13.
Natural low molecular weight organic acids (NLMWOA) have been shown to be useful in enhancing phytoextraction without a high leaching probability. Nevertheless, their efficiency has in many cases been unsatisfactory. The objective of this study was to investigate the reason for the inefficiency of three NLMWOAs (citric acid, oxalic acid and tartaric acid) in enhancing phytoextraction. In several experiments attention was directed not only to the biodegradation of the NLMWOAs, but also to the microorganisms involved, and their influence on the bioavailability of Cu. During a time period of 96 h the biodegradation of the NLMWOAs increased the natural pH-value of the soil by approximately 1 unit and decreased the bioavailability of Cu from 175 mg kg?1 to approximately 140 mg kg?1. As microorganisms were detected with polymerase chain reaction sequencing and with the aid of high performance liquid chromatography measurements, it can be deduced that the fungi, Cordyceps sp., Paecilomyces sp. and the bacteria Burkholderia sp. can degrade all three used NLMOWA. A successive application of the three NLMWOAs to increase the efficiency is therefore not feasible, because with each NLMWOA application the number of microorganisms which can degrade the NLMWOAs increases and thus the degradation is accelerated. These results combined with result from previous studies show that the NLMWOAs are unsuitable in enhancing phytoextraction of heavy metals from the soil.  相似文献   

14.
The effects of the interactions between higher plants and microorganisms and the addition of selected microorganisms on aggregation of sand from an embryo dune were examined. Addition of microorganisms to sand increased both plant growth and the amount of aggregation. Roots alone had little effect on aggregation but in association with microorganisms there was a noticeable increase. The number of microorganisms isolated from aggregates in four different treatments varied each month over the course of the experiment. Aggregates from a treatment receiving Penicillium spores were colonized by the greatest number of microorganisms, and the least colonized aggregates were from a treatment where the sand was initially sterile.  相似文献   

15.
The decline of over-hunted red-legged (Alectoris rufa) and rock (A. graeca) partridge populations has been contrasted with massive releases of captive-reared birds, often hybrids with non-indigenous A. chukar. Released interspecific hybrids raise the risks of introgressive hybridisation, and can contribute to further depress the fitness of native populations. Aiming to assess the extent of hybridisation, we genotyped the mtDNA control-region and eight nuclear microsatellites in 671 red-legged, rock and chukar partridges and hybrids, identified by phenotypic traits. Results reveal a diffuse occurrence of hybridisation: (1) 39 samples (6.2%) show mtDNA haplotypes discordant with their phenotypes, indicating red-legged and chukar mtDNA introgression in native rock partridges; (2) admixture analyses of the microsatellite genotypes identified 32 additional rock partridges (5.1%) hybridised mainly with chukars. We analysed also 39 samples collected from a presumed natural red-legged x rock partridge hybrid zone in the French Alps. Surprisingly, 28% birds showed typical chukar mtDNAs, indicating hybridisation with introduced chukars or hybrids. This hybrid zone led to an introgression cline of chukar alleles into neighbouring Alpine rock partridges detectable up to 100 km, which was shorter than expected by neutral genetic theory, and that suggested natural selection against hybrids. These findings indicate that introgressive hybridisation may disrupt local adaptations in natural red-legged partridge and rock partridge populations, and call for strict control of farming and restocking operations.  相似文献   

16.
Five bacteria (Pseudomonas fluorescens, P. fluorescens subgroup G strain 2, P. marginalis, P. putida subgroup B strain 1 and P. syringae strain 1) and three fungi (Penicillium brevicompactum, P. solitum strain 1 and Trichoderma atroviride) were evaluated to determine their promoting effect on the growth of mature healthy tomato plants grown under hydroponic conditions. P. putida and T. atroviride were shown to improve fruit yields in rockwool and in organic medium. The production or degradation of indole acetic acid (IAA) by the two microorganisms was investigated as possible mechanisms for plant growth stimulation. Both P. putida and T. atroviride were shown to produce IAA. The production of IAA by the two microorganisms was stimulated in vitro by the addition of l-tryptophan, tryptamine and tryptophol (200 μg ml−1) in the culture medium. P. putida and T. atroviride also increased the fresh weight of both the shoot and the roots of tomato seedlings grown in the presence of increasing concentrations of l-tryptophan (up to 0.75 mM). Both microorganisms showed partial degradation of IAA in vitro when grown in a minimal medium with or without sucrose. In addition, the capacity of these microorganisms to reduce the deleterious effect of exogenous IAA was investigated using tomato seedlings. The results showed that the roots of tomato seedlings grown in the presence of increasing concentrations of IAA (0-10 μg ml−1) were significantly longer when seeds were previously treated with P. putida or T. atroviride. The reduction in the detrimental effect of IAA on root elongation could be associated with a reduced ethylene production resulting from a decrease of its precursor 1-aminocyclopropane-1-carboxylic acid (ACC) by microbial degradation of IAA in the rhizosphere and/or by ACC deaminase activity present in both microorganisms.  相似文献   

17.
Qualitative distribution of microorganisms in rhizosphere soils under citrus trees (lemon and orange) was observed by the serial dilution-spread plate method. The maximally represented actinomycete genus was Streptomyces followed by Micromonospora and Nocardia. The streptomycete strains were classified in taxonomical groups by their characteristics. Several cultures produced antibacterial or antifungal antibiotics. Some of the antibiotics have been determined as beta-lactams, polyethers, nonpolyenic macrolides and azalomycin B. Other strains synthesized exoenzymes.  相似文献   

18.
The growth of Eisenia foetida (Savigny) (200–300 mg live weight) was measured on mixtures of inorganic salts, vitamins, and cellulose upon a base of ashed loam or sand. High concentrations of inorganic salts, exceeding an ionic conductivity of about 8mS cm?1 were detrimental, and lower concentrations failed to promote growth.Hatchlings (5 mg live wt) grew to 233 ± 14 mg (SE) on 22 species of bacteria (100 mg dry wt) at 24±1°C, in 8 weeks. There were no significant differences in growth on Gram-negative versus Gram-positive bacteria. Human pathogens were no less nutritive than non-pathogenic species.There was no growth on 6 of 19 species of fungi. Only 31% weight (70 ± 16 mg) was gained per unit weight of fungi as per unit weight of bacteria (100 mg dry microbial biomass).Worms grew as well (274 ± mg) on three species of protozoa as on 22 bacterial species. Growth on any microorganisms tested was less than on activated sludge.E. foetida doubled in weight on the fungus Coriolus hirsutus with the addition of sand or ashed loam. With either of these two forms of grit and microorganisms there was no growth. For growth, a combination of carbohydrate (cellulose), microorganisms and grit appeared necessary. Lyophilized microorganisms had to be washed free of ionic conductivity (and presumably organic residues) from their culture medium for earthworms to grow favorably.  相似文献   

19.
The high biological diversity and the high activity of microorganisms were determined in the extremely arid desert soils developing under very sparse vegetation during the period of rare rains. Green and diatomaceous algae, dinoflagellates, cyanobacteria, and iron bacteria were diagnosed in the edaphon. These microorganisms affect the geochemical processes in the soils, including the biogenic transformation of rock minerals. Amorphous compounds of Fe3+ and Mn3+ are concentrated around the cells of iron bacteria and produce specific iron and iron-manganic pedofeatures. The specific humus-accumulative process is also developed owing to the mineralization of the microbial biomass with the formation of organomineral coagulates in the zones of contact of the intraped mass with rock debris covered by iron films and in the biogenic films on the walls of vesicular pores.  相似文献   

20.
Specific features of the microbial population—the high number of all the groups of microorganisms (1.6 × 103–3.5 × 107) similar to their abundance in steppe soils of the Transbaikal region and the distribution of microorganisms along the soil profile (without a decrease in their number with depth)—were revealed in a cryogenic weakly solodized loamy sandy pale soil. Unlike the soils of the Transbaikal region and central Russia, where bacteria, as a rule, are accumulated in the litter and upper soil horizons, in the undisturbed and weakly disturbed soils of Yakutia, the number of microorganisms is rather high within the whole soil profile. In the strongly disturbed agropale soil of croplands, the distribution of microorganisms is the same as in the soils of the Transbaikal region and European Russia. In the cryogenic soils studied, actinomycetes predominated, and their number varied from 47 000 to 35 000 000 CFU/g of soil. The number of microorganisms positively (r = 1) correlated with the soil moisture.  相似文献   

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