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1.
Seung-Hoon Lee Inyoung Jang Namyi Chae Taejin Choi Hojeong Kang 《Microbial ecology》2013,65(2):405-414
Tundra ecosystem is of importance for its high accumulation of organic carbon and vulnerability to future climate change. Microorganisms play a key role in carbon dynamics of the tundra ecosystem by mineralizing organic carbon. We assessed both ecosystem process rates and community structure of Bacteria, Archaea, and Fungi in different soil layers (surface organic layer and subsurface mineral soil) in an Arctic soil ecosystem located at Spitsbergen, Svalbard during the summer of 2008 by using biochemical and molecular analyses, such as enzymatic assay, terminal restriction fragment length polymorphism (T-RFLP), quantitative polymerase chain reaction (qPCR), and pyrosequencing. Activity of hydrolytic enzymes showed difference according to soil type. For all three microbial communities, the average gene copy number did not significantly differ between soil types. However, archaeal diversities appeared to differ according to soil type, whereas bacterial and fungal diversity indices did not show any variation. Correlation analysis between biogeochemical and microbial parameters exhibited a discriminating pattern according to microbial or soil types. Analysis of the microbial community structure showed that bacterial and archaeal communities have different profiles with unique phylotypes in terms of soil types. Water content and hydrolytic enzymes were found to be related with the structure of bacterial and archaeal communities, whereas soil organic matter (SOM) and total organic carbon (TOC) were related with bacterial communities. The overall results of this study indicate that microbial enzyme activity were generally higher in the organic layer than in mineral soils and that bacterial and archaeal communities differed between the organic layer and mineral soils in the Arctic region. Compared to mineral soil, peat-covered organic layer may represent a hotspot for secondary productivity and nutrient cycling in this ecosystem. 相似文献
2.
J.C. YUSTE J. PEÑUELAS M. ESTIARTE J. GARCIA‐MAS S. MATTANA R. OGAYA M. PUJOL J. SARDANS 《Global Change Biology》2011,17(3):1475-1486
Microbial‐mediated decomposition of soil organic matter (SOM) ultimately makes a considerable contribution to soil respiration, which is typically the main source of CO2 arising from terrestrial ecosystems. Despite this central role in the decomposition of SOM, few studies have been conducted on how climate change may affect the soil microbial community and, furthermore, on how possible climate‐change induced alterations in the ecology of microbial communities may affect soil CO2 emissions. Here we present the results of a seasonal study on soil microbial community structure, SOM decomposition and its temperature sensitivity in two representative Mediterranean ecosystems where precipitation/throughfall exclusion has taken place during the last 10 years. Bacterial and fungal diversity was estimated using the terminal restriction fragment length polymorphism technique. Our results show that fungal diversity was less sensitive to seasonal changes in moisture, temperature and plant activity than bacterial diversity. On the other hand, fungal communities showed the ability to dynamically adapt throughout the seasons. Fungi also coped better with the 10 years of precipitation/throughfall exclusion compared with bacteria. The high resistance of fungal diversity to changes with respect to bacteria may open the controversy as to whether future ‘drier conditions’ for Mediterranean regions might favor fungal dominated microbial communities. Finally, our results indicate that the fungal community exerted a strong influence over the temporal and spatial variability of SOM decomposition and its sensitivity to temperature. The results, therefore, highlight the important role of fungi in the decomposition of terrestrial SOM, especially under the harsh environmental conditions of Mediterranean ecosystems, for which models predict even drier conditions in the future. 相似文献
3.
Drying and rewetting is a frequent physiological stress for soil microbial communities; a stress that is predicted to grow
more influential with future climate change. We investigated the effect of repeated drying–rewetting cycles on bacterial (leucine
incorporation) and fungal (acetate in ergosterol incorporation) growth, on the biomass concentration and composition (PLFA),
and on the soil respiration. Using different plant material amendments, we generated soils with different initial fungal:bacterial
compositions that we exposed to 6–10 repetitions of a drying–rewetting cycle. Drying–rewetting decreased bacterial growth
while fungal growth remained unaffected, resulting in an elevated fungal:bacterial growth ratio. This effect was found irrespective
of the initial fungal:bacterial biomass ratio. Many drying–rewetting cycles did not, however, affect the fungal:bacterial
growth ratio compared to few cycles. The biomass response of the microbial community differed from the growth response, with
fungal and total biomass only being slightly negatively affected by the repeated drying–rewetting. The discrepancy between
growth- and biomass-based assessments underscores that microbial responses to perturbations might previously have been misrepresented
with biomass-based assessments. In light of this, many aspects of environmental microbial ecology may need to be revisited
with attention to what measure of the microbial community is relevant to study. 相似文献
4.
Junxi Hu Meilin Du Jun Chen Liehua Tie Shixing Zhou Kate M. Buckeridge J. Hans C. Cornelissen Congde Huang Yakov Kuzyakov 《Global Change Biology》2023,29(12):3503-3515
Microbial necromass is an important source and component of soil organic matter (SOM), especially within the most stable pools. Global change factors such as anthropogenic nitrogen (N), phosphorus (P), and potassium (K) inputs, climate warming, elevated atmospheric carbon dioxide (eCO2), and periodic precipitation reduction (drought) strongly affect soil microorganisms and consequently, influence microbial necromass formation. The impacts of these global change factors on microbial necromass are poorly understood despite their critical role in the cycling and sequestration of soil carbon (C) and nutrients. Here, we conducted a meta-analysis to reveal general patterns of the effects of nutrient addition, warming, eCO2, and drought on amino sugars (biomarkers of microbial necromass) in soils under croplands, forests, and grasslands. Nitrogen addition combined with P and K increased the content of fungal (+21%), bacterial (+22%), and total amino sugars (+9%), consequently leading to increased SOM formation. Nitrogen addition alone increased solely bacterial necromass (+10%) because the decrease of N limitation stimulated bacterial more than fungal growth. Warming increased bacterial necromass, because bacteria have competitive advantages at high temperatures compared to fungi. Other global change factors (P and NP addition, eCO2, and drought) had minor effects on microbial necromass because of: (i) compensation of the impacts by opposite processes, and (ii) the short duration of experiments compared to the slow microbial necromass turnover. Future studies should focus on: (i) the stronger response of bacterial necromass to N addition and warming compared to that of fungi, and (ii) the increased microbial necromass contribution to SOM accumulation and stability under NPK fertilization, and thereby for negative feedback to climate warming. 相似文献
5.
Mycorrhizal Hyphal Turnover as a Dominant Process for Carbon Input into Soil Organic Matter 总被引:1,自引:0,他引:1
Douglas L. Godbold Marcel R. Hoosbeek Martin Lukac M. Francesca Cotrufo Ivan A. Janssens Reinhart Ceulemans Andrea Polle Eef J. Velthorst Giuseppe Scarascia-Mugnozza Paolo De Angelis Franco Miglietta Alessandro Peressotti 《Plant and Soil》2006,281(1-2):15-24
The atmospheric concentration of CO2 is predicted to reach double current levels by 2075. Detritus from aboveground and belowground plant parts constitutes the
primary source of C for soil organic matter (SOM), and accumulation of SOM in forests may provide a significant mechanism
to mitigate increasing atmospheric CO2 concentrations. In a poplar (three species) plantation exposed to ambient (380 ppm) and elevated (580 ppm) atmospheric CO2 concentrations using a Free Air Carbon Dioxide Enrichment (FACE) system, the relative importance of leaf litter decomposition,
fine root and fungal turnover for C incorporation into SOM was investigated. A technique using cores of soil in which a C4 crop has been grown (δ13C −18.1‰) inserted into the plantation and detritus from C3 trees (δ13C −27 to −30‰) was used to distinguish between old (native soil) and new (tree derived) soil C. In-growth cores using a fine
mesh (39 μm) to prevent in-growth of roots, but allow in-growth of fungal hyphae were used to assess contribution of fine
roots and the mycorrhizal external mycelium to soil C during a period of three growing seasons (1999–2001). Across all species
and treatments, the mycorrhizal external mycelium was the dominant pathway (62%) through which carbon entered the SOM pool,
exceeding the input via leaf litter and fine root turnover. The input via the mycorrhizal external mycelium was not influenced
by elevated CO2, but elevated atmospheric CO2 enhanced soil C inputs via fine root turnover. The turnover of the mycorrhizal external mycelium may be a fundamental mechanism
for the transfer of root-derived C to SOM. 相似文献
6.
Long-Term Phosphorus Fertilization Impacts Soil Fungal and Bacterial Diversity but not AM Fungal Community in Alfalfa 总被引:8,自引:0,他引:8
Soil function may be affected by cropping practices impacting the soil microbial community. The effect of different phosphorus
(P) fertilization rates (0, 20, or 40 kg P2O5 ha−1) on soil microbial diversity was studied in 8-year-old alfalfa monocultures. The hypothesis that P fertilization modifies
soil microbial community was tested using denaturing gradient gel electrophoresis and phospholipids fatty acid (PLFA) profiling
to describe soil bacteria, fungi, and arbuscular mycorrhizal (AM) fungi diversity. Soil parameters related to fertility (soil
phosphate flux, soluble P, moisture, phosphatase and dehydrogenase assays, and carbon and nitrogen content of the light fraction
of soil organic matter) were also monitored and related to soil microbial ribotype profiles. Change in soil P fertility with
the application of fertilizer had no effect on crop yield in 8 years, but on the year of this study was associated with shifts
in the composition of fungal and bacterial communities without affecting their richness, as evidenced by the absence of effect
on the average number of ribotypes detected. However, variation in soil P level created by a history of differential fertilization
did not significantly influence AM fungi ribotype assemblages nor AM fungi biomass measured with the PLFA 16:1ω5. Fertilization
increased P flux and soil soluble P level but reduced soil moisture and soil microbial activity, as revealed by dehydrogenase
assay. Results suggest that soil P fertility management could influence soil processes involving soil microorganisms. Seasonal
variations were also recorded in microbial activity, soil soluble P level as well as in the abundance of specific bacterial
and fungal PLFA indicators of soil microbial biomass. 相似文献
7.
The sedimentary layer deposited at the surface of stormwater infiltration basins is highly organic and multicontaminated.
It undergoes considerable moisture content fluctuations due to the drying and inundation cycles (called hydric dynamics) of
these basins. Little is known about the microflora of the sediments and its dynamics; hence, the purpose of this study is
to describe the physicochemical and biological characteristics of the sediments at different hydric statuses of the infiltration
basin. Sediments were sampled at five time points following rain events and dry periods. They were characterized by physical
(aggregation), chemical (nutrients and heavy metals), and biological (total, bacterial and fungal biomasses, and genotypic
fingerprints of total bacterial and fungal communities) parameters. Data were processed using statistical analyses which indicated
that heavy metal (1,841 μg/g dry weight (DW)) and organic matter (11%) remained stable through time. By contrast, aggregation,
nutrient content (NH4+, 53–717 μg/g DW), pH (6.9–7.4), and biological parameters were shown to vary with sediment water content and sediment biomass,
and were higher consecutive to stormwater flows into the basin (up to 7 mg C/g DW) than during dry periods (0.6 mg C/g DW).
Coinertia analysis revealed that the structure of the bacterial communities is driven by the hydric dynamics of the infiltration
basin, although no such trend was found for fungal communities. Hydric dynamics more than rain events appear to be more relevant
for explaining variations of aggregation, microbial biomass, and shift in the microbial community composition. We concluded
that the hydric dynamics of stormwater infiltration basins greatly affects the structural stability of the sedimentary layer,
the biomass of the microbial community living in it and its dynamics. The decrease in aggregation consecutive to rewetting
probably enhances access to organic matter (OM), explaining the consecutive release of NH4+, the bloom of the microbial biomass, and the change in structure of the bacterial community. These results open new perspectives
for basin management since the risk of OM and pollutant transfer to the aquifer is greatly affected by alternating dry and
flood periods. 相似文献
8.
Elevated Atmospheric CO2 Alters Soil Microbial Communities Associated with Trembling Aspen (Populus tremuloides) Roots 总被引:4,自引:0,他引:4
Global atmospheric CO2 levels are expected to double within the next 50 years. To assess the effects of increased atmospheric CO2 on soil ecosystems, cloned trembling aspen (Populus tremuloides) seedlings were grown individually in 1 m3 open bottom root boxes under either elevated (720 ppm, ELEV) or ambient CO2 (360 ppm, AMB). After 5 years, soil cores (40 cm depth) were collected from the root boxes and divided into 0–20 cm and 20–40
cm fractions. ELEV treatment resulted in significant decreases in both soil nitrate and total soil nitrogen in both the 0–20
cm and 20–40 cm soil fractions, with a 47% decrease in soil nitrate and a 50% decrease in total soil nitrogen occurring in
the 0–20 cm fraction. ELEV treatment did not result in a significant change in the amount of soil microbial biomass. However,
analysis of indicator phospholipid fatty acids (PLFA) indicated that ELEV treatment did result in significant increases in
PLFA indicators for fungi and Gram-negative bacteria in the 0–20 cm fraction. Terminal restriction fragment length polymorphism
(T-RFLP) analysis was used to analyze the composition of the soil bacterial communities (using primers targeting the 16SrRNA
gene) and the soil fungal communities (using primers targeting the intergenic transcribed spacer region). T-RFLP analysis
revealed shifts in both bacterial and fungal community structure, as well as increases in both bacterial and fungal species
richness with ELEV treatment. These results indicated that increased atmospheric CO2 had significant effects on both soil nutrient availability and the community composition of soil microbes associated with
aspen roots. 相似文献
9.
We used sugar maple litter double-labeled with 13C and 15N to quantify fluxes of carbon (C) and nitrogen (N) between litter and soil in a northern hardwood forest and the retention
of litter C and N in soil. Two cohorts of litter were compared, one in which the label was preferentially incorporated into
non-structural tissue and the other structural tissue. Loss of 13C from this litter generally followed dry mass and total C loss whereas loss of 15N (20–30% in 1 year) was accompanied by large increases of total N content of this decaying litter (26–32%). Enrichment of
13C and 15N was detected in soil down to 10–15 cm depth. After 6 months of decay (November–May) 36–43% of the 13C released from the litter was recovered in the soil, with no differences between the structural and non-structural labeled
litter. By October the percentage recovery of litter 13C in soil was much lower (16%). The C released from litter and remaining in soil organic matter (SOM) after 1 year represented
over 30 g C m−2 y−1 of SOM accumulation. Recovery of litter 15N in soil was much higher than for C (over 90%) and in May 15N was mostly in organic horizons whereas by October it was mostly in 0–10 cm mineral soil. A small proportion of this N was
recovered as inorganic N (2–6%). Recovery of 15N in microbial biomass was higher in May (13–15%) than in October (about 5%). The C:N ratio of the SOM and microbial biomass
derived from the labeled litter was much higher for the structural than the non-structural litter and for the forest floor
than mineral SOM, illustrating the interactive role of substrates and microbial activity in regulating the C:N stoichiometry
of forest SOM formation. These results for a forest ecosystem long exposed to chronically high atmospheric N deposition (ca.
10 kg N ha−1 y−1) suggest possible mechanisms of N retention in soil: increased organic N leaching from fresh litter and reduced fungal transport
of N from soil to decaying litter may promote N stabilization in mineral SOM even at a relatively low C:N ratio. 相似文献
10.
氮沉降增加情景下植物-土壤-微生物交互对自然生态系统土壤有机碳的调控研究进展 总被引:1,自引:0,他引:1
大气氮沉降增加倾向于促进受氮限制陆地生态系统地上生物量,但是对地下碳过程和土壤碳截存的影响结果迥异,导致陆地生态系统“氮促碳汇”的评估存在很大的不确定性。大气氮沉降输入直接影响微生物活性或间接影响底物质量,改变凋落物和土壤有机质(SOM)的分解速率和分解程度,进而影响土壤有机碳(SOC)的积累与损耗过程。过去相关研究主要集中在土壤碳转化过程和碳储量动态方面,缺乏植物-微生物-SOM交互作用的理解,对土壤碳截存调控的生物化学和微生物学机理尚不清楚。本文以地下碳循环过程为主线,分别综述了氮沉降增加对植物地下碳分配、SOC激发效应、微生物群落碳代谢过程的影响,深入分析SOM化学稳定性与微生物群落动态的关系。该领域研究的薄弱环节体现在:(1)增氮倾向于降低根系的生长和周转,对根际沉积碳分配(数量和格局)的影响及驱动因素不明确;(2)虽然认识到氮素有效性影响土壤激发效应的方向和强度,但是氧化态NO-3和还原态NH+4输入对有机质激发效应的差异性影响及潜在机理知之甚少;(3)微生物碳利用效率(CUE)是微生物群落碳代谢的关键表征,能够很好地解释土壤碳的积累与损耗过程;由于缺乏适宜的测定方法,难以准确量化土壤微生物的CUE及微生物生物量的周转时间;(4)增氮会抑制土壤真菌群落及其胞外酶活性,对细菌群落组成的影响尚未定论,有关SOM化学质量与土壤微生物群落活性、组成之间的耦合关系尚不清楚。未来研究应基于长期的氮添加控制实验平台,结合碳氧稳定性同位素示踪、有机质化学、分子生物学和宏基因组学等方法,深入分析植物同化碳的地下分配规律、微生物碳代谢和周转、有机质化学结构与功能微生物群落的耦合关系等关键环节。上述研究将有助于揭示植物-土壤-微生物交互作用对SOC动态的调控机制,完善陆地生态系统碳-氮耦合循环模型,有效降低区域陆地碳汇评估的不确定性,并可为陆地生态系统应对全球变化提供科学依据。 相似文献
11.
Soil Microbial Community Response to Drought and Precipitation Variability in the Chihuahuan Desert 总被引:2,自引:0,他引:2
Jeb S. Clark James H. Campbell Heath Grizzle Veronica Acosta-Martìnez John C. Zak 《Microbial ecology》2009,57(2):248-260
Increases in the magnitude and variability of precipitation events have been predicted for the Chihuahuan Desert region of
West Texas. As patterns of moisture inputs and amounts change, soil microbial communities will respond to these alterations
in soil moisture windows. In this study, we examined the soil microbial community structure within three vegetation zones
along the Pine Canyon Watershed, an elevation and vegetation gradient in Big Bend National Park, Chihuahuan Desert. Soil samples
at each site were obtained in mid-winter (January) and in mid-summer (August) for 2 years to capture a component of the variability
in soil temperature and moisture that can occur seasonally and between years along this watershed. Precipitation patterns
and amounts differed substantially between years with a drought characterizing most of the second year. Soils were collected
during the drought period and following a large rainfall event and compared to soil samples collected during a relatively
average season. Structural changes within microbial community in response to site, season, and precipitation patterns were
evaluated using fatty acid methyl ester (FAME) and polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE)
analyses. Fungal FAME amounts differed significantly across seasons and sites and greatly outweighed the quantity of bacterial
and actinomycete FAME levels for all sites and seasons. The highest fungal FAME levels were obtained in the low desert scrub
site and not from the high elevation oak–pine forests. Total bacterial and actinomycete FAME levels did not differ significantly
across season and year within any of the three locations along the watershed. Total bacterial and actinomycete FAME levels
in the low elevation desert-shrub and grassland sites were slightly higher in the winter than in the summer. Microbial community
structure at the high elevation oak–pine forest site was strongly correlated with levels of NH4
+–N, % soil moisture, and amounts of soil organic matter irrespective of season. Microbial community structure at the low elevation
desert scrub and sotol grasslands sites was most strongly related to soil pH with bacterial and actinobacterial FAME levels
accounting for site differences along the gradient. DGGE band counts of amplified soil bacterial DNA were found to differ
significantly across sites and season with the highest band counts found in the mid-elevation grassland site. The least number
of bands was observed in the high elevation oak–pine forest following the large summer-rain event that occurred after a prolonged
drought. Microbial responses to changes in precipitation frequency and amount due to climate change will differ among vegetation
zones along this Chihuahuan Desert watershed gradient. Soil bacterial communities at the mid-elevation grasslands site are
the most vulnerable to changes in precipitation frequency and timing, while fungal community structure is most vulnerable
in the low desert scrub site. The differential susceptibility of the microbial communities to changes in precipitation amounts
along the elevation gradient reflects the interactive effects of the soil moisture window duration following a precipitation
event and differences in soil heat loads. Amounts and types of carbon inputs may not be as important in regulating microbial
structure among vegetation zones within in an arid environment as is the seasonal pattern of soil moisture and the soil heat
load profile that characterizes the location. 相似文献
12.
Guomo Zhou Shunyao Zhuang Qiufang Xu Hua Qin Minghung Wong Zhihong Cao 《The Botanical review》2011,77(3):296-303
Area of bamboo forest (Phyllostachys praecox) has rapidly increased in southern China during the last 20 years due to its high economic value. Aims of this study were
to analyse the temporal and spatial variations of soil organic matter (SOM) in heavily winter mulched bamboo stands and to
estimate potential for carbon sequestration. Total of 60 soil profiles with 0–15 years of bamboo plantation were sampled from
three towns in Lin’an County. Results showed that with increased plantation years, SOM decreased slightly at the beginning
(1–5 years), and then rose up steadily. Based on the average of the three locations, the highest SOM content of 75.82 g/kg
was the surface layer (0–10 cm) of the 15 years. As plantation year increased, the variation of SOM in the surface layer (0–10 cm)
was represented by a parabolic shape, and in the second layer (10–20 cm), it was a similar mode, but less vigorous. Soil organic
carbon (SOC) storage significantly increased during 5 to 15 years after it reached full production, and the calculated annual
SOC increment in 0–40 cm soil profile was about 6.3 t C/ha/year. Therefore, extended Phyllostachys praecox forests can be considered as one option for countering CO2 emissions and regional climate change. 相似文献
13.
Whole soil samples, extracted humic substances, the corresponding fulvic (FA) and humic acids (HA) and the extraction residues
(humins) from long-term, agricultural test plots were investigated by in-source pyrolysis-field ionization mass spectrometry
(Py-FIMS). For the soils distinct differences in the chemical composition of the organic matter in differently managed fields
were observed. The FI mass spectra of the extracted humic substances gave complementary chemical information, as they cover
a larger mass range compared to the whole soil spectra. The chemical, structural information of the conventional alkaline
extraction residues was demonstrated by Py-FIMS spectra to be similar to that of the related soil samples.
Influences of mineral matrix to organic matter ratios were studied on mixtures of extracted humic substances with defined
mineral components such as quartz, basalt, iron oxide (Fe2O3), Ca-montmorillonite, kaolinite and illite. It was shown that in these mixtures the number of mass signals detected and the
covered mass range decreased, when organic carbon concentrations (Corg) in this synthetic mineral matrix dropped below 2% (w/w). Limitations in the direct application of Py-FIMS might arise in
the case of natural soil samples with Corg concentrations below 0.5% (w/w), high contents of swelling clay minerals and iron oxides. ei]{gnR}{fnMerckx} 相似文献
14.
土壤有机质概念和分组技术研究进展 总被引:63,自引:2,他引:63
土壤有机质一直是土壤学研究领域的重点,在过去的50年里,对土壤质量可持续性观念的增强和寻找快速判断人为因素对土壤质量影响方向指标的强烈愿望导致了土壤有机质的研究重点发生了急剧变化:对农业措施反映慢的土壤腐殖质类物质的研究正在退出土壤有机质研究领域,而侧重点逐渐转向了土壤中未受微生物作用或正在受微生物降解的有机残体;也出现了新的土壤有机质研究概念和对应测试手段:土壤有机质的比重分组、与有机质结合的土壤颗粒大小分组、土壤团聚体中的POM和iPOM以及土壤水溶性有机质和微生物体C等概念和测试手段被相继提了出来,土壤有机质的研究重点正在从土壤微生物的作用产物(腐殖质)向土壤微生物作用前的、具有部分生物活性的有机质(轻组有机质、砂粒组和粗粉砂粒组中的有机质、POM和iPOM)和完全具有生物活性的有机质(微生物体C和水溶性有机质)转移,这一过程与土壤有机质概念的拓展密不可分。 相似文献
15.
Microbial Protein in Soil: Influence of Extraction Method and C Amendment on Extraction and Recovery
The capacity to study the content and resolve the dynamics of the proteome of diverse microbial communities would help to
revolutionize the way microbiologists study the function and activity of microorganisms in soil. To better understand the
limitations of a proteomic approach to studying soil microbial communities, we characterized extractable soil microbial proteins
using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Two methods were utilized to extract proteins
from microorganisms residing in a Quitman and Benfield soil: (1) direct extraction of bulk protein from soil and (2) separation
of the microorganisms from soil using density gradient centrifugation and subsequent extraction (DGC–EXT) of microbial protein.
In addition, glucose and toluene amendments to soil were used to stimulate the growth of a subset of the microbial community.
A bacterial culture and bovine serum albumin (BSA) were added to the soil to qualitatively assess their recovery following
extraction. Direct extraction and resolution of microbial proteins using SDS-PAGE generally resulted in smeared and unresolved
banding patterns on gels. DGC–EXT of microbial protein from soil followed by separation using SDS-PAGE, however, did resolve
six to 10 bands in the Benfield but not the Quitman soil. DGC–EXT of microbial protein, but not direct extraction following
the addition of glucose and toluene, markedly increased the number of bands (~40) on the gels in both Benfield and Quitman
soils. Low recoveries of added culture and BSA proteins using the direct extraction method suggest that proteins either bind
to soil organic matter and mineral particles or that partial degradation takes place during extraction. Interestingly, DGC
may have been preferentially selected for actively growing cells, as gauged by the 10–100× lower cy19:0/18:1ω7 ratio of the
fatty acid methyl esters in the isolated community compared to that for the whole soil. DGC can be used to isolate soil communities
and provide microbial protein that can be characterized using PAGE. 相似文献
16.
William A. Argiroff Donald R. Zak Rima A. Upchurch Sydney O. Salley A. Stuart Grandy 《Global Change Biology》2019,25(12):4369-4382
Fine root litter is a primary source of soil organic matter (SOM), which is a globally important pool of C that is responsive to climate change. We previously established that ~20 years of experimental nitrogen (N) deposition has slowed fine root decay and increased the storage of soil carbon (C; +18%) across a widespread northern hardwood forest ecosystem. However, the microbial mechanisms that have directly slowed fine root decay are unknown. Here, we show that experimental N deposition has decreased the relative abundance of Agaricales fungi (?31%) and increased that of partially ligninolytic Actinobacteria (+24%) on decaying fine roots. Moreover, experimental N deposition has increased the relative abundance of lignin‐derived compounds residing in SOM (+53%), and this biochemical response is significantly related to shifts in both fungal and bacterial community composition. Specifically, the accumulation of lignin‐derived compounds in SOM is negatively related to the relative abundance of ligninolytic Mycena and Kuehneromyces fungi, and positively related to Microbacteriaceae. Our findings suggest that by altering the composition of microbial communities on decaying fine roots such that their capacity for lignin degradation is reduced, experimental N deposition has slowed fine root litter decay, and increased the contribution of lignin‐derived compounds from fine roots to SOM. The microbial responses we observed may explain widespread findings that anthropogenic N deposition increases soil C storage in terrestrial ecosystems. More broadly, our findings directly link composition to function in soil microbial communities, and implicate compositional shifts in mediating biogeochemical processes of global significance. 相似文献
17.
The ectomycorrhizal symbiosis alters the physicochemical and biological conditions in the surrounding soil, thus creating
a particular environment called ectomycorrhizosphere, which selects microbial communities suspected to play a role in gross
production and nutrient cycling. To assess the ectomycorrhizosphere effect on the structure of microbial communities potentially
involved in the mobilization of nutrients from the soil minerals in a poor-nutrient environment, we compared the functional
diversity of soil and ectomycorrhizosphere bacterial communities in a forest stand. Two hundred and sixty-four bacterial strains
and 107 fungal strains were isolated from the bulk soil of an oak (Quercus petraea) stand and from oak–Scleroderma citrinum ectomycorrhizosphere and ectomycorrhizae, in two soil organo-mineral horizons (0 to 3 cm and 5 to 10 cm). They were characterized
using two in vitro tests related to their capacities to mobilize iron and phosphorus. We demonstrated that the oak–S. citrinum ectomycorrhizosphere significantly structures the culturable bacterial communities in the two soil horizons by selecting
very efficient strains for phosphorus and iron mobilization. This effect was also observed on the diversity of the phosphate-solubilizing
fungal communities in the lower soil horizon. A previous study already demonstrated that Laccaria bicolor–Douglas fir ectomycorrhizosphere structures the functional diversity of Pseudomonas fluorescens population in a forest nursery soil. Comparing to it, our work highlights the consistency of the mycorrhizosphere effect
on the functional diversity of bacterial and fungal communities in relation to the mineral weathering process, no matter the
fungal symbiont, the age and species of the host tree, or the environment (nursery vs forest). We also demonstrated that the
intensity of phosphorus and iron mobilization by the ectomycorrhizosphere bacteria isolated from the lower soil horizon was
significantly higher compared to that which was isolated from the upper horizon. This reveals for the first time a stratification
of the functional diversity of the culturable soil bacterial communities as related to phosphorus and iron mobilization. 相似文献
18.
Soil Water Content and Organic Carbon Availability Are Major Determinants of Soil Microbial Community Composition 总被引:9,自引:0,他引:9
Exploration of environmental factors governing soil microbial community composition is long overdue and now possible with improved methods for characterizing microbial communities. Previously, we observed that rice soil microbial communities were distinctly different from tomato soil microbial communities, despite management and seasonal variations within soil type. Potential contributing factors included types and amounts of organic inputs, organic carbon content, and timing and amounts of water inputs. Of these, both soil water content and organic carbon availability were highly correlated with observed differences in composition. We examined how organic carbon amendment (compost, vetch, or no amendment) and water additions (from air dry to flooded) affect microbial community composition. Using canonical correspondence analysis of phospholipid fatty acid data, we determined flooded, carbon-amended (+C) microcosm samples were distinctly different from other +C samples and unamended (–C) samples. Although flooding without organic carbon addition influenced composition some, organic carbon addition was necessary to substantially alter community composition. Organic carbon availability had the same general effects on microbial communities regardless of whether it was compost or vetch in origin. In addition, flooded samples, regardless of organic carbon inputs, had significantly lower ratios of fungal to bacterial biomarkers, whereas under drier conditions and increased organic carbon availability the microbial communities had higher proportions of fungal biomass. When comparing field and microcosm soil, flooded +C microcosm samples were most similar to field-collected rice soil, whereas all other treatments were more similar to field-collected tomato soil. Overall, manipulating water and carbon content selected for microbial communities similar to those observed when the same factors were manipulated at the field scale. 相似文献
19.
Long-term Effect of Municipal Solid Waste Amendment on Microbial Abundance and Humus-associated Enzyme Activities Under Semiarid Conditions 总被引:4,自引:0,他引:4
Microbial ecology is the key to understanding the function of soil biota for organic matter cycling after a single amendment
of organic waste in semiarid soils. Therefore, in this paper, the long-term effect (17 years) of adding different doses of
a solid municipal waste to an arid soil on humus–enzyme complexes, a very stable and long-lasting fraction of soil enzymes,
as well as on microbial and plant abundance, was studied. Humic substances were extracted by 0.1 M pH 7 sodium pyrophosphate
from soil samples collected in experimental plots amended with different doses of a solid municipal waste (0, 65, 130, 195,
and 260 t/ha) 17 years before. The activity of different hydrolases related with the C (β-glucosidase), N (urease), and P
(alkaline phosphatase) cycles and with the formation of humic substances (o-diphenol oxidase) were determined in this extract. The density and diversity of plant cover in the plots, as well as the
fungal and bacterial biomass (by analyzing phopholipid fatty acids) were also determined. In general, the amended plots showed
greater humic substance-related enzymatic activity than the unamended plots. This activity increased with the dose but only
up to a certain level, above which it leveled off or even diminished. Plant diversity and cover density followed the same
trend. Fungal and bacterial biomass also benefited in a dose-dependent manner. Different signature molecules representing
gram+ and gram− bacteria, and those corresponding to monounsaturated and saturated fatty acids showed a similar behavior.
The results demonstrate that organic amendment had a noticeable long-term effect on the vegetal development, humic substances-related
enzyme activity and on the development of bacteria and fungi in semiarid conditions. 相似文献
20.
Response of Oxidative Enzyme Activities to Nitrogen Deposition Affects Soil Concentrations of Dissolved Organic Carbon 总被引:10,自引:0,他引:10
Recent evidence suggests that atmospheric nitrate (NO
3
−
) deposition can alter soil carbon (C) storage by directly affecting the activity of lignin-degrading soil fungi. In a laboratory
experiment, we studied the direct influence of increasing soil NO
3
−
concentration on microbial C cycling in three different ecosystems: black oak–white oak (BOWO), sugar maple–red oak (SMRO),
and sugar maple–basswood (SMBW). These ecosystems span a broad range of litter biochemistry and recalcitrance; the BOWO ecosystem
contains the highest litter lignin content, SMRO had intermediate lignin content, and SMBW leaf litter has the lowest lignin
content. We hypothesized that increasing soil solution NO
3
−
would reduce lignolytic activity in the BOWO ecosystem, due to a high abundance of white-rot fungi and lignin-rich leaf litter.
Due to the low lignin content of litter in the SMBW, we further reasoned that the NO
3
−
repression of lignolytic activity would be less dramatic due to a lower relative abundance of white-rot basidiomycetes; the
response in the SMRO ecosystem should be intermediate. We increased soil solution NO
3
−
concentrations in a 73-day laboratory incubation and measured microbial respiration and soil solution dissolved organic carbon
(DOC) and phenolics concentrations. At the end of the incubation, we measured the activity of β-glucosidase, N-acetyl-glucosaminidase,
phenol oxidase, and peroxidase, which are extracellular enzymes involved with cellulose and lignin degradation. We quantified
the fungal biomass, and we also used fungal ribosomal intergenic spacer analysis (RISA) to gain insight into fungal community
composition. In the BOWO ecosystem, increasing NO
3
−
significantly decreased oxidative enzyme activities (−30% to −54%) and increased DOC (+32% upper limit) and phenolic (+77%
upper limit) concentrations. In the SMRO ecosystem, we observed a significant decrease in phenol oxidase activity (−73% lower
limit) and an increase in soluble phenolic concentrations (+57% upper limit) in response to increasing NO
3
−
in soil solution, but there was no significant change in DOC concentration. In contrast to these patterns, increasing soil
solution NO
3
−
in the SMBW soil resulted in significantly greater phenol oxidase activity (+700% upper limit) and a trend toward lower DOC
production (−52% lower limit). Nitrate concentration had no effect on microbial respiration or β-glucosidase or N-acetyl-glucosaminidase
activities. Fungal abundance and basidiomycete diversity tended to be highest in the BOWO soil and lowest in the SMBW, but
neither displayed a consistent response to NO
3
−
additions. Taken together, our results demonstrate that oxidative enzyme production by microbial communities responds directly
to NO
3
−
deposition, controlling extracellular enzyme activity and DOC flux. The regulation of oxidative enzymes by different microbial
communities in response to NO
3
−
deposition highlights the fact that the composition and function of soil microbial communities directly control ecosystem-level
responses to environmental change. 相似文献