首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 593 毫秒
1.
《Soil biology & biochemistry》2001,33(12-13):1817-1826
A selection of soil bacteria was screened for their ability to interfere with carpogenic germination of Sclerotinia sclerotiorum. Nine out of 300 bacterial isolates were found to significantly suppress apothecial formation. One of these isolates, identified as a strain of Serratia plymuthica, was highly effective in inducing complete suppression of apothecial formation at high concentrations, and also strongly inhibited the germination of ascospores as well as hyphal growth of S. sclerotiorum. A bioassay-guided purification procedure starting with the cell-free supernatant of the bacterial culture led to the identification of a chlorinated macrolide as an active compound able to induce the observed inhibition. Spectroscopic data showed the compound to be identical to haterumalide A. The data presented show the ability of this compound to inhibit apothecial formation and ascospore germination. Other possible mechanisms involved in inhibition of apothecial formation and mycelial and hyphal growth of S. sclerotiorum by the same isolate are discussed. The relevance of our observations to natural systems will be the subject of further research.  相似文献   

2.
A microbiological examination of manganese concretions which were found in an alfisol soil of West Peloponnese, Greece, is presented. Two new Mn2+ oxidizing bacteria identified as Pseudomonas sp. nov. (E1) and Citrobacter freundii (E4) were isolated from the core of the concretions. The Mn2+ oxidizing activity of the isolates was demonstrated on solidified media. The quantitative determination of Mn2+ precipitation was performed by activation analysis and atomic absorption spectrophotometry. The mechanism of Mn2+ precipitation was studied using whole cell, and cell-free extracts of both bacteria; a precipitation of 50% and 70%, respectively, occurred without any change in the pH. The precipitation of Mn2+ depended on the concentration of the whole cells and of the cell-free extracts and was independent of the presence of Mn during the growth of the cultures. The activity of cell-free extracts is heat sensitive and inhibited by HgCl2.The porosity of the concretions and the presence of amorphous manganese oxides in them, together with the morphology and physiology of the bacteria isolated from the core of them, present good evidence that those bacteria play an important role in the formation of the examined concretions.  相似文献   

3.
Plant growth promotion by Azospirillum brasilense SM has been attributed to its indole-3-acetic acid (IAA) production. Analysis of IAA biosynthesis by this strain under nutrient stresses, likely environmental fluctuations and long-term batch cultures suggested that they significantly influenced this function, with some conditions (fluctuations in temperature) triggering IAA accumulation. In long-term batch cultures (of 30 days), the bacterial population was maintained at a specific cell density and produced IAA even after a sharp decline in population size, albeit fluctuations were observed in both the parameters. Long-term bacterial cultures under nitrogen starvation showed the same trend in cell viability; however, a continuous increase in IAA accumulation was seen over time. This study has shown that A. brasilense strain SM has the potential to be a competent rhizospheric bacterium as it can beneficially influence the growth of sorghum. Further, it also has the ability to promote the growth of a number of other plants like mung bean, maize, and wheat. The benefit of this characteristic of strain SM can be directly accrued to a range of plants with which it may associate so as to improve their yield.  相似文献   

4.
With the aim to explore the possible role of mineral phosphate-solubilizing bacteria (PSB) in phosphorus (P) cycling in iron-rich, acidic soils, we conducted a survey of PSB naturally colonizing a limonitic crust in the south-east region of Venezuela (Bolívar State). A total of 130 heterotrophic bacterial isolates showing different degrees of mineral tri-calcium phosphate (Ca3(PO4)2)-solubilizing activities were isolated from NBRIP plates. In contrast, no isolates showing iron phosphate (FePO4)- or aluminum phosphate (AlPO4)-solubilizing activities were detected by this experimental approach. The 10 best Ca3(PO4)2-solubilizers were selected for further characterization. These isolates were shown to belong to the genera Burkholderia, Serratia, Ralstonia and Pantoea by partial sequencing analysis of their respective 16S rRNA genes. All the PSB isolates were able to mediate almost complete solubilization of Ca3(PO4)2 in liquid cultures; in contrast, the PSB isolates were less effective when solubilizing FePO4. Two groups of PSB isolates were clearly differentiated on the basis of their Ca3(PO4)2 solubilization kinetics. Acidification of culture supernatants seemed to be the main mechanism for P solubilization. Indeed, gluconic acid was shown to be present in the supernatant of five isolates. Furthermore, detection of genes involved in the production of this organic acid was possible in three isolates by means of a PCR protocol.  相似文献   

5.
Mixed populations of microorganisms growing in a recycling soil percolator produced N-nitrosoiminodiacetate (NIDA) after 30 days growth using sodium nitrilotriacetate (NTA), a detergent additive, and NaNO3 as C and N source respectively. Control experiments using autoclaved soil or substituting either acetate (C source) or NH+4 (N source) did not show any N-nitroso derivative production. Five distinct strains of microorganisms were isolated which could grow on an NTA/NO?3 minimal medium but none produced NIDA in pure culture. Mixed cultures of two strains of Pseudomonas produced NIDA after 4 days percolation, using glass beads as a support. Cell-free extracts of the mixed cultures synthesized NIDA after 30 min incubation at 30°C with an activity of 27 μmoles NIDA produced/mg protein h?1. Physical separation of the two organisms and the cell-free extracts by a dialysis membrane in a chamber determined that only one of the two organisms was responsible for the synthesis of NIDA, but the production was dependent upon the presence of the other organism. The possible relationship between the two organisms is discussed.  相似文献   

6.
Microorganisms are frequently exposed to flowing fluid, thus to investigate bacterial characteristics under different hydrodynamic conditions is of great importance in microbial ecology. This study characterized bacterial growth and phenol biodegradation of three strains, i.e., Microbacterium oxydans (rod-shaped, non-motile), Alcaligenes faecalis (rod-shaped, motile), and Staphylococcus haemolyticus (spherical, non-motile) in shake-flask cultures at various rotating speeds. For all the strains, a higher rotating speed always resulted in a shorter lag phase, indicating that the strains showed a superior adaptability under higher hydrodynamic conditions. The maximum specific growth rate of M. oxydans, A. faecalis, and S. haemolyticus increased rapidly with the increase of energy dissipation rate till the highest value of 0.386, 0.240, and 0.323 1/h and then decreased as the rotating speed further increased. The phenol biodegradation rate was also dependent on rotating speed, and the trends were consistent with the growth rate variations. A predictive model similar to Haldane model was proposed and was fitted well (R2?>?0.913) with bacterial growth under different hydrodynamic conditions. According to the predictive model, the optimum hydrodynamic conditions for the growth of M. oxydans, A. faecalis, and S. haemolyticus were 3.099, 2.197, and 2.289 m2/s3, respectively. The results suggested that non-motile and rod-shaped bacteria were more dependent on hydrodynamic conditions than motile and spherical ones, which could be attributed to the discrepancies in bacterial morphology and motility. The results provide a better understanding on bacterial responses to various hydrodynamic conditions and could be further applied in the bioremediation of contaminated water.  相似文献   

7.
 The production of auxins [indoleacetic acid (IAA) and related compounds] by Azospirillum brasilense and Klebsiella pneumoniae in culture media supplemented with tryptophan was investigated. Extracts from the supernatants of cultures incubated for different periods of time were partitioned into two fractions and each fraction was analysed separately by using HPLC. The chromatography was performed by using different optimized mobile phases and corresponding standards. Both N-fixing strains produced high quantities of extracellular IAA and tryptophol. The production of both compounds increased during the stationary phase of the culture. However, very low levels of indoleacetaldehyde and indolepyruvate produced by K. pneumoniae in the exponential phase of the culture, were only recorded when the samples were analysed immediately after the extraction. In addition, the effect of different concentrations of filter-sterilized culture supernatants of both strains on the development of rice roots grown in hydroponic culture medium was studied. Addition of the optimum concentrations (6–8%) of bacterial supernatants to such hydroponic cultures increased root elongation, root surface area, root dry matter and development of lateral roots and root hairs compared to untreated roots. On the other hand, the addition of high concentrations of the supernatant (more than 10%) strongly inhibited root elongation, lateral root development, and caused root outgrowths, i.e. round nodule-like tumours. Received: 7 January 1998  相似文献   

8.
In well-aerated culture solutions Ca-montmorillonite at 0.25% concentration markedly accelerated and increased growth, glucose consumption and CO2 evolution by various Streptomyces, Micromonospora and Nocardia species. The montmorillonite was a little more active than Ca-humate and was usually still but somewhat less effective when confined to dialysis tubing. Ca-exchange resin, Na2SiO3 and finely powdered CaCO3 exerted very little or no effect. In many cultures the relation of glucose consumption to biomass formation indicated a more efficient use of the glucose C for cell synthesis in the presence of clay. In other cultures the greater biomass formation was associated with a more rapid and complete utilization of the glucose present.  相似文献   

9.
Polycyclic aromatic hydrocarbons (PAH) are ubiquitous pollutants that are toxic and recalcitrant to degradation by bacteria. This research evaluated the toxicity of different concentrations [10, 20, 40, 60, 80 and 100 μg mL−1] of phenanthrene (PHE) or benzo[a]pyrene (BaP) on the growth of Rhizobium tropici CIAT899 under in vitro conditions as well as the potential degradation of PHE and BaP by this bacterium. At 24 h, a 40% decrease in Rhizobium growth was observed when exposed to 40 μg mL−1 of either PHE or BaP. Furthermore, bacterial growth was completely inhibited by PHE or BaP applied in 80 and 100 μg mL−1. After 96 h, the growth of R. tropici at 40 μg PHE mL−1 or 60 μg BaP mL−1 was similar to those treatments without PAH. To evaluate R. tropici degrading capabilities, supernatants of cultures with 40 μg PHE mL−1 or 60 μg BaP mL−1 were analyzed by gas chromatography coupled to mass spectrophotometer (GC–MS). R. tropici was able to degrade either PHE or BaP diminishing its concentration in 20% and 25% during the first 24 h, degradation obtained at 120 h was 50% and 45% for PHE or BaP, respectively. This research shows for the first time that R. tropici CIAT 899 grows in liquid culture medium contaminated with PAH, and moreover is able to growth and to degrade either PHE or BaP.  相似文献   

10.
The current study aimed to compare lindane degradation by pure and mixed cultures of Streptomyces sp. Cell-free extracts were assayed for potentiating dechlorinase activity and, based on these results, consortia of two to six microorganisms were assayed for their growth on and degradation of lindane. Furthermore, the role of bacterial consortia of lindane-degrading strains was examined in lindane decontamination soil assays. Four actinobacteria, previously isolated from a pesticide-contaminated area, were selected because of their tolerance to lindane and their ability to use the pesticide as sole carbon source. These strains as well as Streptomyces sp. M7 and Streptomyces coelicolor A3 were used to study specific dechlorinase activity (SDA) and lindane removal in mixed cultures. Pure cultures presented SDA in the presence of 1.66 mg L-1 lindane as carbon source. SDA was improved by certain mixed cultures until 12 times compared with pure cultures. Mixed cultures with two, three, and four strains showed maximum lindane removal of 46% to 68%, whereas combinations of five and six strains did not efficiently remove the pesticide from the culture medium. The Streptomyces sp. A2, A5, M7, and A11 consortium presented the lowest ratio between residual lindane concentration and SDA and could be a promising tool for lindane biodegradation.  相似文献   

11.
The effect of bacteria represented by indigenous soil microflora or a mixture of soil bacteria Pseudomonas aeruginosa and Rhodococcus erythropolis on fungal growth, extracellular enzyme production and polycyclic aromatic hydrocarbons (PAHs) biodegradation efficiency in soil of white-rot fungi Trametes versicolor and Irpex lacteus was investigated. Both fungi were able to colonize soil. The growth yields measured by ergosterol were about two-fold in I. lacteus after 10 weeks. Laccase was produced in T. versicolor cultures in the presence or absence of bacteria but live bacteria reduced the laccase levels in soil about 5 times. Manganese-dependent peroxidase (MnP) was not detected in T. versicolor cultures. The amounts of MnP and laccase in I. lacteus cultures were not affected by the presence of bacteria. T. versicolor was more efficient in PAH removal for all PAHs tested although its capacity to colonize soil was lower. The removal rates of PAHs by T. versicolor in sterile soil were 1.5-fold, 5.8-fold and 1.8-fold for 2-3-ring, 4-ring and 5-6-ring PAHs, compared to I. lacteus, respectively. I. lacteus showed a low efficiency of removal of pyrene, benzo[a]anthracene and benzo[k]fluoranthene, compared to T. versicolor, whereas chrysene and benzo[b]fluoranthene were degraded by neither fungus. The main effect of the presence of the indigenous microflora or R. erythropolis and P. aeruginosa was a significant decrease of degradation of total PAHs by both T. versicolor and I. lacteus. Weak fungal/bacterial synergistic effects were observed in the case of removal of acenapthylene, benzo[a]pyrene, dibenzo[a,h]anthracene and benzo[g,h,i]perylene by I. lacteus and acenapthylene by T. versicolor. However, the bacterial effects were different in the two fungi. PAH abiotic losses represented 15 and 21% of the total PAHs after 5 and 10 weeks, respectively; naphthalene and acenaphthene were removed from the soil due to volatilization.  相似文献   

12.
The ability of Pleurotus eryngii, Pleurotus ostreatus, Pleurotus pulmonarius and Pleurotus sajor-caju to degrade the aromatic pollutants 2,4-dichorophenol (2,4-DCP) and benzo(a)pyrene [B(a)P] in liquid culture and microcosm (using wheat straw as growth substrate and sea sand as a xenobiotic carrier) was investigated by HPLC and 14CO2 release from labeled pollutants. We found that 100 μM 2,4-DCP was very quickly transformed by the four fungi, disappearing 24 h after its addition to the liquid cultures. However, a 2-week incubation period was required to transform 100 μM B(a)P up to 75% by P. eryngii and P. pulmonarius. Whereas the fungi were able to begin degradation of the two pollutants with high transformation rates, their complete degradation (mineralization) rates were very low. Mineralization of B(a)P in liquid cultures was only observed with P. eryngii and P. pulmonarius, although the four Pleurotus species studied were able to mineralize this compound in solid state fermentation (SSF). The ligninolytic enzymes laccase and versatile peroxidase (VP), together with aryl-alcohol oxidase (AAO) providing extracellular H2O2, were found in liquid cultures. Except AAO, these enzymes were also detected in SSF experiments. In order to investigate the role of ligninolytic enzymes in the process, their action on both pollutants (50 μM) was studied in vitro in the absence and presence of redox mediators. As observed with the fungal cultures, 2,4-DCP was oxidized faster than B(a)P by both laccase (60% transformation after 6 h) and VP (100% transformation after 1 h). Moreover, laccase oxidation was strongly increased (up to 90% transformation after 3 h), by the presence of the mediators 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) or 1-hydroxybenzotriazole (HBT). In the case of B(a)P, the presence of ABTS or HBT was strictly required for oxidation by laccase (25% transformation after 8 h). Degradation of B(a)P was also observed in reactions with VP (40% transformation after 6 h). The results obtained suggest that Pleurotus species can be used in applications focused to the degradation of aromatic pollutants using wheat straw as a growth substrate, and provide the first evidence on the direct transformation of recalcitrant aromatic pollutants by VP.  相似文献   

13.
The l-lactic acid obtained from a whey waste valorization process decreased pH and increased phosphate solubilization of a Plagic Antrosol soil. This behavior was reversible due to the complete and rapid degradation of lactic acid by soil microorganisms, leading to a strong soil biological stimulation. Both dehydrogenase (DHA) and acid phosphomonoesterase (APA) activities were also significantly stimulated, due to the stimulation of microbial activity, whereas the β-glucosidase activity was unaffected. There was also a shift in bacterial biodiversity with growth of bacterial strains using lactic acid as a C source. The bacteria enriched belonged to the plant growth-promoting bacteria (PGPb), such as Rhizobium and Azotobacter genus, involved in N2 fixation, and Pseudomonas and Bacillus genera, involved in phosphorous bioavailability. We conclude that lactic acid application improves fertility parameters on soils. Further research at field scale is needed to confirm these results.  相似文献   

14.
The biodegradability of dissolved organic carbon (DOC) in different fractions from the forest floor was studied. Soil leachate (SL, the soil solution in macropores which is freely drained from forest floor after rainfall), the soil matrix solution (SMS, the soil solution in meso-/micropores of the soil matrix), and soil water extracts (SWE) from two different beech forest floors were compared. Zero-tension and tension lysimeters were used to collect SL and SMS, respectively. Loss of DOC (during 21 days) and respiration of CO2-C (during 7 days) were used as conventional measures of the availability of DOC. Bacterial production, measured using the leucine incorporation technique, and bacterial growth efficiency were also estimated. All methods were used to study differences in biodegradability between plots with and without ground flora (Deschampsia flexuosa or Anemone nemorosa) and different type of forest floor (with an organic (O) horizon or a mull (A) horizon). There were no differences in bioavailability of DOC from soil solutions extracted from plots with and without ground flora. The bioavailability of DOC in the different collected soil solutions varied, however. DOC in SWE was the most available, with a mean of 39% of DOC-loss in 21 days, and 18% of DOC being respired in 7 days. DOC in soil matrix solution was the least available of the soil solutions (7% respired), significantly less than DOC in soil leachate (11% respired). The methods measuring biodegradation of DOC, DOC-loss and CO2-C respiration gave similar results and were comparable to bacterial production and bacterial growth efficiency, with the exception of SWE from the O-horizon at the D. flexuosa site, which had low bacterial production and bacterial growth efficiency, indicating a limitation of the bacterial growth. This study is one of the first to use bacterial production and bacterial growth efficiency for measuring bioavailability in terrestrial environments, giving an extra dimension for the process of biodegradation of DOC.  相似文献   

15.

Purpose

The purpose of this study was to determine the first-order rate constants and half-lives of aerobic and anaerobic biomineralization of atrazine in soil samples from an agricultural farm site that had been previously used for mixing pesticide formulations and washing application equipment. Atrazine catabolic genes and atrazine-degrading bacteria in the soil samples were analyzed by molecular methods.

Materials and methods

Biomineralization of atrazine was measured in soil samples with a [U-ring-14C]-atrazine biometer technique in soil samples. Enrichment cultures growing with atrazine were derived from soil samples and they were analyzed for bacterial diversity by constructing 16S rDNA clone libraries and sequencing. Bacterial isolates were also obtained and they were screened for atrazine catabolic genes.

Results and discussion

The soils contained active atrazine-metabolizing microbial communities and both aerobic and anaerobic biomineralization of [U-ring-14C]-atrazine to 14CO2 was demonstrated. In contrast to aerobic incubations, anaerobic biometers displayed considerable differences in the kinetics of atrazine mineralization between duplicates. Sequence analysis of 16S rDNA clone libraries constructed from the enrichment cultures revealed a preponderance of Variovorax spp. (51 %) and Schlesneria (16 %). Analysis of 16S rRNA gene sequences from pure cultures (n?=?12) isolated from enrichment cultures yielded almost exclusively Arthrobacter spp. (83 %; 10/12 isolates). PCR screening of pure culture isolates for atrazine catabolic genes detected atzB, atzC, trzD, trzN, and possibly atzA. The presence of a complete metabolic pathway was not demonstrated by the amplification of catabolic genes among these isolates.

Conclusions

The soils contained active atrazine-metabolizing microbial communities. The anaerobic biometer data showed variable response of atrazine biomineralization to external electron acceptor conditions. Partial pathways are inevitable in soil microbial communities, with metabolites linking into other catabolic and assimilative pathways of carbon and nitrogen. There was no evidence for the complete set of functional genes of the known pathways of atrazine biomineralization among the isolates.
  相似文献   

16.
Environmentally friendly control measures are needed for the soil-borne pathogen, Pythium ultimum. This pathogen can cause severe losses to field- and greenhouse-grown cucumber and other cucurbits. Live cells and ethanol extracts of cultures of the bacterium Serratia marcescens N4-5 provided significant suppression of damping-off of cucumber caused by P. ultimum when applied as a seed treatment. Live cells of this bacterium also suppressed damping-off caused by P. ultimum on cantaloupe, muskmelon, and pumpkin. Culture filtrates from strain N4-5 contained chitinase and protease activities while ethanol extracts contained the antibiotic prodigiosin, the surfactant serrawettin W1, and possibly other unidentified surfactants. Production of prodigiosin and serrawettin W1 was temperature-dependent, both compounds being detected in extracts from N4-5 grown at 28 °C but not in extracts from N4-5 grown at 37 °C. Ethanol extracts from strain N4-5 grown at 28 °C inhibited germination of sporangia and mycelial growth by P. ultimum in in vitro experiments. There was no in vitro inhibition of P. ultimum associated with ethanol extracts of strain N4-5 grown at 37 °C. Prodigiosin, purified from two consecutive thin-layer chromatography runs using different solvent systems, inhibited germination of sporangia and mycelial growth of P. ultimum. Another unidentified compound(s) also inhibited germination of sporangia but did not inhibit mycelial growth. There was no in vitro inhibition associated with serrawettin W1. These results demonstrate that live cells and cell-free extracts of S. marcescens N4-5 are effective for suppression of damping-off of cucumber caused by P. ultimum possibly due in part to the production of the antibiotic prodigiosin.  相似文献   

17.
Endophytic microbial communities can have strong influence on the growth of their host plants. The present study reports a diazotrophic endophytic bacterial species that colonizes predominantly Pennisetum glaucum (pearl millet) and remains stabilized throughout the latter's various growth stages under field conditions. Qualitative and quantitative changes in the endophytic bacterial population structure were examined during the plant growth period at regular intervals of 7 days up to harvesting. DNA fingerprinting (ERIC-PCR) was used as a biomarker to track the identity of various isolates obtained at different time intervals. Identification of representative bacterial species corresponding to different ERIC types was made on the basis of 16S rRNA gene sequence analysis. Based on the colony forming unit (cfu) count of bacterial isolates observed at various growth stages, Pseudomonas aeruginosa PM389 was found to be the dominant diazotrophic species among the cultivable endophytes colonizing pearl millet. The population of P. aeruginosa was detected in the host 21 days after sowing (DAS), indicating its entry in plant roots from soil and suggesting its non-vertical transfer in pearl millet. Moreover, an upward migration of this dominant diazotrophic bacterial species to shoots was observed with the plant growth. Further evaluation of P. aeruginosa PM389 revealed its various plant growth promoting properties viz. nitrogen fixation, mineral phosphate solubilization, siderophore production and antagonistic properties.  相似文献   

18.

Purpose

This work was conducted to determine whether Nickel-resistant rhizosphere bacteria (NiRRB) affected the Ni uptake and hyperaccumulation by Noccaea caerulescens.

Material and methods

Ni-resistant bacterial strains (10 mM Ni), Bacillus pumilus and Micrococcus spp., were originally isolated from the rhizosphere of N. caerulescens (Brassicaceae) collected from serpentine Ni-rich soil in the Vosges mountains (France). They served to inoculate axenic seeds of N. caerulescens, which were then sown aseptically into sterile soil Magenta boxes and cultured under controlled conditions.

Results and discussion

Cultures inoculated with NiRRB showed a disappearance of chlorosis signs and a significant increase of the aerial biomass compared to the axenic control (1.5-fold higher). Despite the drastic decrease of the water-extractable Ni in the soil (80 %) at the end of the growth, there was no significant effect on Ni accumulation by N. caerulescens compared to the axenic control. A highly significant promoting effect on plant growth (fourfold higher) and an increase of Ni accumulation (65-fold higher) by N. caerulescens were shown in cultures with native microorganisms (nonsterile control) compared to the axenic control.

Conclusions

The NiRRB strains used in this study reduced Ni bioavailability in the soil and did not improve the Ni uptake by N. caerulescens. Nevertheless, they induced promoting effects on the growth of this plant. They could serve as an effective metal-immobilizing and growth-promoting bioinoculant for plants in Ni-stressed soils. Optimal growth and Ni uptake by N. caerulescens requires the presence of native microbial community.  相似文献   

19.
Thirty-nine endophytic bacterial strains were isolated from the nodule of Lespedeza sp. grown in two different locations of South Korea. All strains were checked for their plant growth promoting (PGP) abilities under in vitro conditions. Most of the isolates showed multiple PGP activity, i.e., indole acetic acid production, ACC deaminase activity, siderophore production, and phosphate solubilization. The strains were identified by using 16S rRNA gene sequence analysis as belonging to Alphaproteobacteria, Betaproteobacteria, Actinobacteria, and Firmicutes phylum with nine different genera Arthrobacter, Bacillus, Bradyrhizobium, Burkholderia, Dyella, Methylobacterium, Microbacterium, Rhizobium, and Staphylococcus. Gene nodA amplification showed positive results only for strains from Bradyrhizobium and Rhizobium genera. The strains from Bradyrhizobium and Rhizobium genera enhanced plant growth, nodulation, and acetylene reduction activity when inoculated on Vigna unguiculata L. (cowpea), whereas other strains did not induce nodule formation but enhanced plant growth. Herbaceous legume Lespedeza sp. formed root nodules with diverse bacterial group, and probably, these bacteria can be used for stimulating plant growth.  相似文献   

20.
Microbial ferric iron reduction, with organic carbon or hydrogen as the electron donor, is one of the most important biogeochemical processes in anoxic paddy soils; however, the diversity and community structure of hydrogen-dependent dissimilatory iron-reducers remain unknown. Potential H2-dependent Fe(III)-reducing bacteria in paddy soils were explored using enrichment cultures with ferrihydrite or goethite as the electron acceptor and hydrogen as the electron donor. Terminal restriction fragment length polymorphism (T-RFLP) analysis and cloning/sequencing were conducted to reveal bacterial community structure. Results showed that Geobacter and Clostridium were the dominant bacteria in the enrichment cultures. Fe(III) oxide mineral phases showed a strong effect on the community structure; Geobacter and Clostridium were dominant in the ferrihydrite treatment, while Clostridium spp. were dominant in the goethite treatment. These suggested that H2-dependent Fe(III)-reducing bacteria might be widely distributed in paddy soils and that besides Geobacter, Clostridium spp. might also be an important group of H2-dependent Fe(III)-reducing microorganisms.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号