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1.
The aims of this study were to investigate soil microbial community characteristics and their interrelationships with soil geochemistry under different farmlands in Shouguang, China. The traditional dilution plate counts, BIOLOG system, and fatty acid methyl ester (FAME) analyses were used to assess microbial populations, substrate utilization, and fatty acid profiles. The number of aerobic heterotrophic bacteria varied significantly among untilled land, maize, and mungbean fields. The amounts of actinomycetes, fungal fatty acids, and Gram-positive/Gram-negative bacteria ratios varied greatly among celery, tomato, and aubergine fields. In the tomato field, the soil microbial community characteristics were significantly different from other fields. Principal component analysis of BIOLOG and FAME data revealed differences in the catabolic capability and fatty acid profiles of soil microbial communities among different farmlands. Spearman correlation analyses showed that in these sand clay soils of Shouguang, microbial communities in different farmlands were closely correlated with soil geochemical elements, moisture, and organic matter.  相似文献   

2.
黄河三角洲退化湿地微生物群落特性研究   总被引:4,自引:0,他引:4  
Five different sites with a soluble salt gradient of 3.0--17.7 g kg-1 dry soil from the coast to the inland were selected, and the microbial population size, activity and diversity in the rhizospheres of five common plant species and the adjacent bulk soils (non-rhizosphere) were compared in a degraded wetland of the Yellow River Delta, Shandong Province, China to study the effects of soil environment (salinity, seasonality, depth, and rhizosphere) on microbial communities and the wetland’s ecological function, thus providing basic data for the bioremediation of degraded wetlands. There was a significant negative linear relationship between the salinity and the total number of microorganisms, overall microbial activity, or culturable microbial diversity. Salinity adversely affected the microbial community, and higher salinity levels resulted in smaller and less active microbial communities. Seasonal changes were observed in microbial activity but did not occur in the size and diversity. The microbial size, activity and diversity decreased with increasing soil depth. The size, activity and diversity of culturable microorganisms increased in the rhizospheres. All rhizospheres had positive effects on the microbial communities, and common seepweed had the highest rhizosphere effect. Three halophilic bacteria (Pseudomonas mendocina, Burkholderia glumae, and Acinetobacter johnsonii) were separated through BIOLOG identification, and common seepweed could be recommended for bioremediation of degraded wetlands in the Yellow River Delta.  相似文献   

3.
High arsenic (As) and chromium (Cr) concentrations are currently receiving attention because of their negative effects on the environment and human health. Microorganisms inhabiting contaminated environments have developed resistance mechanisms against the toxicity of these pollutants. Indeed, members of the bacterial genus Micrococcus have been isolated from different toxic metal-contaminated environments; however, knowledge concerning its resistance mechanisms to As and Cr toxicity remains lim...  相似文献   

4.
The phylogenetic diversity of phosphate solubilizing bacteria(PSB)distributed in P-rich soils in the Dianchi Lake drainage area of China was characterized,and the tricalcium phosphate(TCP)solubilizing activities of isolated PSB were determined.Among 1 328 bacteria isolated from 100 P-rich soil samples,377 isolates(28.39%of the total)that exhibited TCP solubilization activity were taken as PSB.These PSB showed different abilities to solubilize TCP,with the concentrations of solubilized P in bacterial cultures varying from 33.48 to 69.63 mg L-1.A total of 123 PSB isolates,with relatively high TCP solubilization activity(>54.00 mg L-1),were submitted for restriction fragment length polymorphism(RFLP)analysis,which revealed 32 unique RFLP patterns.Based on these patterns,62 representative isolates,one to three from each RFLP pattern,were seffected for 16S rRNA sequencing.Phylogenetic analysis placed the 123 PSB into three bacterial phyla,namely Proteobacteria,Actinobacteria and Firmicutes.Members of Proteobacteria were the dominant PSB,where 107 isolates represented by 26 RFLP patterns were associated with the genera of Burkholderia,Pseudomonas,Acinetobacter,Enterobacter,Pantoea,Serratia,Klebsiella,Leclercia,Raoultella and Cedecea.Firmicutes were the subdominant group,in which 13 isolates were affiliated with the genera of Bacillus and Brevibacterium.The remaining 3 isolates were identified as three species of the genus Arthrobacter.This research extends the knowledge on PSB in P-rich soils and broadens the spectrum of PSB for the development of environmentally friendly biophosphate fertilizers.  相似文献   

5.
To identify plant growth promotion ability of phosphorus-solubilizing native bacteria, we have examined a collection of isolates representing the diversity of culturable phosphate-solubilizing bacteria from acid soils of the northeast of Argentina. Assays in growth medium supplemented with tricalcium phosphate revealed different phosphorus solubilization activity and temporal patterns of solubilization. Acidification of the broth medium coincided with phosphorus solubilization. The isolates were grouped according to their Rep fingerprinting profiles and phylogenetically classified by 16S rDNA and biochemical analyses. These isolates were assigned to the genera Enterobacter, Pantoea, Pseudomonas, Acinetobacter, Burkholderia, and Exiguobacterium. Four isolates showing high phosphorus solubilizing activity in in vitro assays were inoculated on common beans (Phaseolus vulgaris); some of them promoted plant growth and increased photosynthesis and the P and N content of leaves. The results indicated that the ability to in vitro solubilize P is not necessarily associated to the promotion of plant growth.  相似文献   

6.
Myxobacter strain 8 is one component of a sequence of three predatory bacteria that develop in soil when Micrococcus luteus host cells are added to the soil. The survival of strain 8 in the presence and absence of added host cells in natural soil not allowed to dry out was examined. Strain 8 vegetative cells died relatively rapidly in unamended soil. Death was faster and occurred to a greater extent in acidic than in neutral pH soil. However, in both cases death was accompanied by formation of sonication-resistant myxospores so that they comprised the ultimate population. These myxospores survived for prolonged periods in both acidic and neutral pH soils.Vegetative cells added in high numbers to soil did not multiply under any of the conditions tested. They did multiply, however, when they were added in low numbers to soil (including acidic soil) receiving sequential (additive) amendments of heart infusion broth or living M. luteus cells. This multiplication produced strain 8 cell numbers approximating those in the above experiments receiving high strain 8 cell number inoculations. Possibly, this represents a maximum vegetative cell number for soil.Germination of the myxospores in soil, followed by growth, seemed to require an approximately neutral pH and the presence of a proper host organism. Germination occurred with M. luteus as host, but not with Escherichia coli. A delayed germination occurred when sequential amendments of heart infusion broth, instead of M. luteus host cells, were made, but this could reflect a growth response by some indigenous components of the soil microflora that then served as host cells for germination.  相似文献   

7.
Differences in the culturable fractions of total and metal-tolerant bacteria inhabiting bulk soil of a metal-mine spoil heap and the rhizosphere of silver birch (Betula pendula) or bushgrass (Calamagrostis epigejos), completed with changes in total microbial community structure in the soil, were assessed by MIDI-FAME (fatty acid methyl ester) profiling of whole-cell fatty acids. In addition, the abundance of metal-tolerant populations among the culturable bacterial communities and their identity and the metal-tolerance patterns were determined. The high proportions of Cu- and Zn-tolerant bacteria that ranged from 60.6% to 94.8% were ascertained in the heap sites. Within 31 bacterial isolates obtained, 24 strains were Gram-positive and Arthrobacter, Bacillus, Rathayibacter, Brochothrix, and Staphylococcus represented those identified. Minimum inhibitory concentration (MIC) data indicated that several strains developed multi-metal tolerance, and the highest tolerance to Cu (10 mM) and Zn (12 mM) was found for Pseudomonas putida TP3 and three isolated strains (BS3, TP12, and SL16), respectively. The analysis of FAME profiles obtained from the culturable bacterial communities showed that Gram-positive bacteria predominated in bulk soil of all heap sites. In contrast, the rhizosphere communities showed a lower proportion of the Gram-positive group, especially for silver birch. For the total microbial community, mostly Gram-negative bacteria (e.g., Pseudomonas) inhabited the heap sites. The results suggest that the quantitative and qualitative development of heterotrophic microbiota in the soil of the metal-mine spoil heap seems to be site-dependent (i.e., rhizosphere vs. bulk soil), according to differences in the site characteristics (e.g., enrichment of nutrients and total metal concentrations) and impact of plant species.  相似文献   

8.
Fifty-seven bacteria were isolated from soil suspensions incubated under pO2 of 1.5 or 159 mm Hg and their growth and generic characteristics were elucidated.The isolates were cultured under both high (159 mm Hg) and low (3 mm Hg) pO2. On the basis of their growth responses to the different pO2, the isolates were classified into two types; (A-type) the lag time, specific growth rate, and/or maximum growth depended on pO2, and (B-type) these three growth characteristics did not depend on pO2. B-types were found only among isolates from soil suspensions incubated under the low pO2. The respiration of some B-type isolates was inhibited by higher pO2. No A-type isolates were inhibited by high pO2.The isolates were classified into eight generic groups: Under 159 mm Hg O2, Groups I(Bacillus spp) and IV(Pseudomonas spp etc.) dominated the others; under 1.5 mm Hg O2, Group I, III(coryneform bacteria) and V(Alcaligenes spp etc.) dominated. Microaerophilic isolates (isolated only from the soil suspension incubated under 1.5 mm Hg O2) were classified into Group V. Isolates belonging to the B-type were classified into the coryneform and Group V bacteria.  相似文献   

9.
The influence of humic acids of different origins on the growth of bacterial cultures of different taxa isolated from the soil and the digestive tracts of earthworms (Aporrectodea caliginosa)—habitats with contrasting conditions—was studied. More than half of the soil and intestinal isolates from the 170 tested strains grew on the humic acid of brown coal as the only carbon source. The specific growth rate of the bacteria isolated from the intestines of the earthworms was higher than that of the soil bacteria. The use of humic acids by intestinal bacteria confirms the possibility of symbiotic digestion by earthworms with the participation of bacterial symbionts. Humic acids at a concentration of 0.1 g/l stimulated the growth of the soil and intestinal bacteria strains (66 strains out of 161) on Czapek’s medium with glucose (1 g/l), probably, acting as a regulator of the cell metabolism. On the medium with the humic acid, the intestinal bacteria grew faster than the soil isolates did. The most active growth of the intestinal isolates was observed by Paenibacillus sp., Pseudomonas putida, Delftia acidovorans, Microbacterium terregens, and Aeromonas sp.; among the soil ones were the representatives of the Pseudomonas genus. A response of the bacteria to the influence of humic acids was shown at the strain level using the example of Pseudomonas representatives. The Flexom humin preparation stimulated the growth of the hydrocarbon-oxidizing Acinetobacter sp. bacteria. This effect can be used for creating a new compound with the elevated activity of bacteria that are destroyers of oil and oil products.  相似文献   

10.
Diversity of denitrifying microflora and ability to reduce N2O in two soils   总被引:1,自引:0,他引:1  
 The ozone-depleting gas N2O is an intermediate in denitrification, the biological reduction of NO3 to the gaseous products N2O and N2 gas. The molar ratio of N2O produced (N2O/N2O+N2) varies temporally and spatially, and in some soils N2O may be the dominant end product of denitrification. The fraction of NO3 -N emitted as N2O may be due at least in part to the abundance and activity of denitrifying bacteria which possess N2O reductase. In this study, we enumerated NO3 -reducing and denitrifying bacteria, and compared and contrasted collections of denitrifying bacteria isolated from two agricultural soils, one (Auxonne, soil A) with N2O as the dominant product of denitrification, the other (Chalons, soil C) with N2 gas as the dominant product. Isolates were tested for the ability to reduce N2O, and the presence of the N2O reductase (nosZ)-like gene was evaluated by polymerase chain reaction (PCR) using specific primers coupled with DNA hybridization using a specific probe. The diversity and phylogenetic relationships of members of the collections were established by PCR/restriction fragment length polymorphism of 16s rDNA. The two soils had similar numbers of bacteria which used NO3 as a terminal electron acceptor anaerobically. However, the soil A had many more denitrifiers which reduced NO3 to gaseous products (N2O or N2) than did soil C. Collections of 258 and 281 bacteria able to grow anaerobically in the presence of NO3 were isolated from soil A and soil C, respectively. These two collections contained 66 and 12 denitrifying isolates, respectively, the others reducing NO3 only as far as NO2 . The presence of nosZ sequences was generally a poor predictor of N2O reducing ability: there was agreement between the occurrence of nosZ sequences and the N2O reducing ability for only 42% of the isolates; 35% of the isolates (found exclusively in soil A) without detectable nosZ sequences reduced N2O whereas 21% of the isolates carrying nosZ sequences did not reduce this gas under our assay conditions. Twenty-eight different 16S rDNA restriction patterns (using two restriction endonucleases) were distinguished among the 78 denitrifying isolates. Two types of patterns appeared to be common to both soils. Twenty-three and three types of patterns were found exclusively among bacteria isolated from soils A and C, respectively. The specific composition of denitrifying communities appeared to be different between the two soils studied. This may partly explain the differences in the behaviour of the soils concerning N2O reduction during denitrification. Received: 31 October 1997  相似文献   

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