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1.
Morales M Arancibia J Lemus M Silva J Gentina JC Aroca G 《Biotechnology letters》2011,33(11):2141-2145
Sulfolobus metallicus is a hyperthermophilic and chemolithoautotrophic archaeon that uses elemental sulfur as an energy source. Its ability to
oxidize H2S was measured either in the presence or absence of elemental sulphur, showing its ability for using both as an energy source.
A biotrickling filter was set up and a biofilm of S. metallicus was established over the support. The maximum removal capacity of the biotrickling filter reached at 55°C was 40 g S/m3h for input loads higher than 70 g S/m3h. Thus, S. metallicus can be used in a biofiltration system for the treatment of waste gas emissions at high temperatures contaminated with H2S. 相似文献
2.
Settled zoospores of the green macroalga Enteromorpha intestinalis were subjected to several different freezing and storing
treatments at both cryogenic and non-cryogenic temperatures after which their viability was assessed using a spore germination
bioassay. Three different cooling rates were tested: slow cooling at –1°C min−1 and –0.5°C min−1 to end temperatures in the range –20°C to –40°C, and a two-step procedure whereby the spores were frozen to –30°C at a rate
of –1°C min−1 prior to immersion in liquid nitrogen at –196°C. Spore viability was also investigated using the cryoprotectants glycerol
and dimethyl suphoxide (DMSO), a reduced saline medium and various storage times. In the majority of experiments, the use
of a cryoprotectant during the freezing process significantly increased the viability of the spores, with DMSO affording slightly
greater protection than glycerol. All treatments produced high viabilities (ranging from 75.3–100.0%) after 5-min storage
at the different end temperatures. However, progressively longer storage up to 7 days generally resulted in a marked reduction
in viability. This was with the exception of spores frozen in a reduced saline medium; a medium of 75% seawater and either
5 or 10% DMSO greatly increased spore viability, with values of > 40% recorded for spores stored at –20°C for up to 5 weeks.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
A. V. Bryanskaya Z. B. Namsaraev O. M. Kalashnikova D. D. Barkhutova B. B. Namsaraev V. M. Gorlenko 《Microbiology》2006,75(5):611-620
The structure and production characteristics of microbial communities from the Urinskii alkaline hot spring (Buryat Republic, Russia) have been investigated. A distinctive characteristic of this hot spring is the lack of sulfide in the issuing water. The water temperature near the spring vents ranged from 69 to 38.5°C and pH values ranged from 8.8 to 9.2. The total mineralization of water was less than 0.1 g/liter. Temperature has a profound effect on the species composition and biogeochemical processes occurring in the algal-bacterial mats of the Urinskii hot spring. The maximum diversity of the phototrophic community was observed at the temperatures 40 and 46°C. A total of 12 species of cyanobacteria, 4 species of diatoms, and one species of thermophilic anoxygenic phototrophic bacteria, Chloroflexus aurantiacus, have been isolated from mat samples. At temperatures above 40°C, the filamentous cyanobacterium Phormidium laminosum was predominant; its cell number and biomass concentration comprised 95.1 and 63.9%, respectively. At lower temperatures, the biomass concentrations of the cyanobacterium Oscillatoria limosa and diatoms increased (50.2 and 36.4%, respectively). The cyanobacterium Mastigocladus laminosus, which is normally found in neutral or slightly acidic hydrothermal systems, was detected in microbial communities. As the diatom concentration increases, so does the dry matter concentration in mats, while the content of organic matter decreases. The concentrations of proteins and carbohydrates reached their maximum levels at 45–50°C. The maximum average rate of oxygenic photosynthesis [2.1 g C/(m2 day)], chlorophyll a content (343.4 mg/m2), and cell number of phototrophic microorganisms were observed at temperatures from 45 to 50°C. The peak mass of bacterial mats (56.75 g/m2) occurred at a temperature of 65–60°C. The maximum biomass concentration of phototrophs (414.63 × 10?6 g/ml) and the peak rate of anoxygenic photosynthesis [0.42 g C/(m2 day)] were observed at a temperature of 35–40°C. 相似文献
4.
Summary. Heat shock proteins (HSPs) are synthesised by cells subsequent to a stress exposure and are known to confer protection to
the cell in response to a second challenge. HSP induction and decay are correlated to thermotolerance and may therefore be
used as a biomarker of thermal history. The current study tested the temperature-dependent nature of the heat shock response
and characterised its time profile of induction. Whole blood from 6 healthy males (Age: 26 ± (SD) 2 yrs; Body mass 74.2 ±
3.8 kgs; VO2max: 49.1 ± 4.0 ml·kg−1·min−1) were isolated and exposed to in vitro heat shock (HS) at 37, 38, 39, 40, and 41 °C for a period of 90 min. After HS the
temperature was returned to 37 °C and intracellular HSP70 was quantified from the leukocytes at 0, 2, 4, and 6 h after heat
treatment. The concentration of HSP70 was not different between temperatures (P > 0.05), but the time-profile of HSP70 synthesis appeared temperature-dependent. At control (37 °C) and lower temperatures
(38–39 °C) the mean HSP70 concentration increased up to 4 h post HS (P < 0.05) and then returned towards baseline values by 6 h post HS. With in vitro hyperthermic conditions (40–41 °C), the time-profile
was characterised by a sharp rise in HSP70 levels immediately after treatment (P < 0.05 for 40 °C at 0 h), followed by a progressive decline over time. The results suggest a temperature-dependent time-profile
of HSP70 synthesis. In addition, the temperature at which HSP70 is inducted might be lower than 37 °C. 相似文献
5.
Biofilms growing on ice and benthic mats are among the most conspicuous biological communities in Antarctic landscapes and
harbour a high diversity of organisms. These communities are consortia that make important contributions to carbon and nitrogen
input in non-marine Antarctic ecosystems. Here, we study the effect of increasing temperatures on the carbon and nitrogen
metabolism of two benthic communities on Byers Peninsula (Livingston Island, Maritime Antarctica): a biofilm dominated by
green algae growing on seasonal ice, and a land-based microbial mat composed mainly of cyanobacteria. Inorganic carbon photoassimilation,
urea and nitrate uptake and N2-fixation (acetylene reduction activity) rates were determined in situ in parallel at five different temperatures (0, 5, 10,
15, 25°C) using thermostatic baths. The results for the cyanobacterial mat showed that photosynthesis and N2-fixation responded positively to increased temperatures, but urea and NO3− uptake rates did not show a significant variation related to temperature. This microbial mat exhibits relatively low activity
at 0°C whereas at higher temperatures (up to 15°C), N2-fixation rate increased significantly. Similarly, the maximum photosynthetic activity increased in parallel with temperature
and showed no saturation up to 25°C. In contrast, the ice biofilm displayed higher photosynthetic activity at 0°C than at
the other temperatures assayed, and it showed elevated photoinhibition at warmer temperatures. 相似文献
6.
S. K. Schmidt D. R. Nemergut A. E. Miller K. R. Freeman A. J. King A. Seimon 《Extremophiles : life under extreme conditions》2009,13(5):807-816
High-elevation periglacial soils are among the most extreme soil systems on Earth and may be good analogs for the polar regions
of Mars where oligotrophic mineral soils abut with polar ice caps. Here we report on preliminary studies carried out during
an expedition to an area where recent glacial retreat has exposed porous mineral soils to extreme, daily freeze–thaw cycles
and high UV fluxes. We used in situ methods to show that inorganic nitrogen (NO3
− and NH4
+) was being actively cycled even during a period when diurnal soil temperatures (5 cm depth) ranged from −12 to 27°C and when
sub-zero, soil cooling rates reached 1.8°C h−1 (the most rapid soil cooling rates recorded to date). Furthermore, phylogenetic analyses of microbial phylotypes present
at our highest sites (5410 m above sea level) showed the presence of nitrifying bacteria of the genus Nitrospira and newly discovered nitrite-oxidizing Betaproteobacteria. These soils were overwhelmingly dominated (>70% of phylotypes)
by photosynthetic bacteria that were related to novel cyanobacteria previously found almost exclusively in other plant-free,
high-elevation soils. We also demonstrated that soils from our highest sites had higher potential for mineralizing glutamate
and higher microbial biomass than lower elevation soils that had been more recently covered by ice. Overall, our findings
indicate that a diverse and robustly functioning microbial ecosystem is present in these previously unstudied high-elevation
soils. 相似文献
7.
In this study, the kinetic behaviors between n-butyl acetate and composite bead were investigated. Both microbial growth rate and biochemical reaction rate would be inhibited with increasing average inlet concentration. The order of the inhibitive effect, which resulted from increased average inlet concentration for four operation temperatures, was 30>35>40>25 °C. Both microbial growth rate and biochemical reaction rate would be enhanced and inhibited with increasing operation temperature in the operation temperature ranges of 25 to 30 and 30 to 40 °C, respectively. The enhancing and inhibitive effects resulting from increased operation temperature were the most pronounced at the average inlet concentration of 200 ppm. The values of maximum reaction rate V
m and half-saturation constant K
s ranged from 0.011 to 0.047 g C h−1 kg−1 packed material and from 19.30 to 62.40 ppm, respectively. The zero-order kinetic with the diffusion rate limitation could be regarded as the most adequate biochemical reaction kinetic model. The values of maximum elimination capacity ranged from 0.51 to 0.20 g C h−1 kg−1 packed material, and the optimal maximum elimination capacity of biofilter occurred at the operation temperature of 30 °C. 相似文献
8.
G. Selvakumar S. Kundu Piyush Joshi Sehar Nazim A. D. Gupta H. S. Gupta 《Indian journal of microbiology》2010,50(1):50-56
Exiguobacterium acetylicum strain 1P (MTCC 8707) is a gram-positive, rod-shaped, yellow pigmented bacterium isolated from soil on nutrient agar plates
at 4°C. The identity of the bacterium was arrived on the basis of the biochemical characterization, BIOLOG sugar utilization
pattern and sequencing of the 16S rRNA gene. It grew at temperatures ranging from 4 to 42°C, with temperature optima at 30°C.
It expressed multiple plant growth promotion attributes such as phosphate solubilization, indole acetic acid (IAA), siderophore
and hydrogen cyanide (HCN) production, differentially at suboptimal growth temperatures (15 and 4°C). At 15°C it solubilized
phosphate (21.1 μg of P ml−1 day−1), and produced IAA (14.9 μg ml−1 day−1) in tryptophan amended media. Qualitative detection of siderophore production and HCN were possible at 15°C. At 4°C it retained
all the plant growth promotion attributes. Seed bacterization with the isolate, positively influenced the growth and nutrient
uptake parameters of wheat seedlings in glass house studies at suboptimal cold growing temperatures. 相似文献
9.
Exponential growth of “snow molds” at sub-zero temperatures: an explanation for high beneath-snow respiration rates and Q
10 values 总被引:2,自引:0,他引:2
Numerous studies have demonstrated exceptionally high temperature sensitivity of the beneath-snow respiratory flux in cold-winter
ecosystems. The most common, but still untested, explanation for this high sensitivity is a physical one based on the observation
that water availability in soils increases exponentially as soils warm from −3 to 0°C. Here, we present evidence for a biological
hypothesis to explain exponential kinetics and high Q
10 values as beneath-snow soils warm from −3 to 0°C during the early spring in a high-elevation subalpine forest. First, we
show that some of the dominant organisms of the beneath-snow microbial community, “snow molds”, exhibit robust exponential
growth at temperatures from −3 to −0.3°C. Second, Q
10 values based on growth rates across the temperature range of −2 to −0.3°C for these snow molds vary from 22 to 330. Third,
we derive an analytical equation that combines the relative contributions of microbial growth and microbial metabolism to
the temperature sensitivity of respiration. Finally, we use this equation to show that with only moderate snow mold growth
(several generations), the combined sensitivities of growth and metabolism to small changes in beneath-snow soil temperature,
create a double exponential in the Q
10 function that may explain the extremely high (~1 × 106) Q
10 values observed in past studies. Our biological explanation for high Q
10 levels is supported by several independent studies that have demonstrated build up of microbial biomass under the snow as
temperatures warm from −2 to 0°C. 相似文献
10.
Summary A laboratory study was conducted to find out the effect of temperatures on rice seedling emergence under different levels
of bulk density. The temperatures ranging from 10 to 40°C in increments of 5°C were maintained constant with ±1°C accuracy.
The bulk density levels were 1.3, 1.5, 1.7, and 1.9 g cm−3. Aluminum cylinders with top open and bottom provided with a removable 20-mesh brass screen, were used as soil containers.
The moisture content in soil was always above field capacity which could be accomplished by placing the cylinders in a tray
in which water level was maintained constant to 5 cm depth.
Seedling emergence counts were taken till the 10th day of seeding. At the end of the experiment, observations on root and
shoot elongations were recorded. Emergence was maximum at 25 and 30°C under 1.3 and 1.5 g cm−3, and decreased at 35, 20, and 15°C. As compared to the lower bulk densities, the reduction in emergence under 1.7 g cm−3 was smaller at 25 and 30°C than at 35°C. This was ascribed to greater seedling vigour at 25 and 30°C, as could be inferred
from larger root and shoot elongation. The reduction in emergence at lower temperatures (20 and 15°C) might be due to delay
in time of germination as well as less seedling vigour. The soil under 1.9 g cm−3 was sufficiently dense that the seedlings could not emerge except a few ones at 25 and 30°C. 相似文献
11.
Biodegradation of nonylphenol in a continuous bioreactor at low temperatures and effects on the microbial population 总被引:6,自引:0,他引:6
A packed-bed bioreactor inoculated with a mixed culture obtained from a contaminated site was used to continuously treat a
saturated solution of nonylphenol. The reactor was operated at feeding rates of 13–112 ml h−1 and temperatures of 5.5, 10, and 15°C. Optimal bioreactor performance was achieved at 10°C and at a feeding rate of 84 ml
h−1 (with a removal rate of 43 mg l−1 day−1 of nonylphenol). No endocrine activity was observed in the effluent of the bioreactor at any of the temperatures tested,
and the only metabolic products found were branched carboxylic acids and alkanes (lacking an aromatic ring). The study of
the microbial populations in the biofilm at the three temperatures tested using fluorescence in situ hybridization showed
that all the bacterial species that could be identified belonged to the phylum Proteobacteria. The most abundant class identified at all three temperatures was β-Proteobacteria. The proportions of bacteria that bound to the specific probes among the total population, identified with the bacterial
probe EUB338MIX, were 60, 43, and 24% at 15, 10, and 5.5°C, respectively. 相似文献
12.
A study of heat effects was performed in thylakoids and photosystem II (PSII)-enriched membranes isolated from spinach in
relation to Cl−-induced activation of PSII catalyzed oxygen evolution and the retention of Cl− in the PSII complex. For this, Cl−-sufficient membranes and low-Cl− membranes were used. The presence of Cl− in the reaction medium did accelerate oxygen evolution, which remained unaffected by heat treatment up to 40°C in PSII membranes
and up to 42.5°C in thylakoids. Heat resistance of Cl−-induced activation of oxygen evolution was found to be independent of the presence of ‘bound Cl−’ in the preparations. However, the functional stability of the PSII complex during heat treatment showed a marked dependence
on the presence of bound Cl− in PSII. Electron paramagnetic resonance study of manganese (Mn) release per reaction center/YD+ showed that there was little loss of Mn2+ up to 42°C in our preparations, although the PSII activity was significantly lowered. These observations together with data
from steady state chlorophyll a fluorescence imply that the site of action of Cl− causing direct activation of oxygen evolution was different from the site of primary heat damage. A differential response
of chloride binding sites to heat stress was observed. The high-affinity (tightly bound, slow exchanging) site of chloride
is affected earlier (∼37°C) while low-affinity (loosely bound, fast exchanging) site gets affected at higher temperatures
(42.5°C in thylakoids and 40°C in the case of PSII-enriched membranes).
Prasanna Mohanty is an INSA Honorary Scientist and Professor on Courtesy, DAVV, Indore. 相似文献
13.
Rosa Martínez 《Polar Biology》1996,16(7):483-489
The activity of the respiratory Electron Transfer System (ETS) was measured in total microplankton (<200-μm size fraction)
and nanoplankton (<20-μm size fraction) from the Bransfield Strait, during the ECOANTAR 1993–1994 cruise of the Spanish B.I.O.
Hespérides in January 1994. Activity variation in response to temperature was measured at three stations belonging to three different
water masses that showed in situ temperatures ranging from −0.57 to 1.30°C. Subsamples from each station were assayed for ETS activity at 11 temperatures in the −3 to 20°C range. The results showed a bimodal activity-temperature variation in plankton from the lower in situ temperatures, with
a peak in activity at 0°C, and a minimum at 3°C, with subsequent continuous increase up to absolute maxima at 15°C. The water mass with higher than 0°C temperature did not show the 0°C activity peak. The results suggest the existence, in water masses with in situ temperature near or below 0°C, of psychrophilic microbial populations with a narrow temperature range of respiratory enzyme activity, coexisting with
more numerous and widespread psychrotrophs, or cold-tolerant populations, whose ETSs showed a continuous increase in activity
in the −3 to 15°C temperature range. Arrhenius activation energies (Ea) of total microplankton ranged from 3 to 17 kcal mole-1, and the Q10 from 1.2 to 3.5. These facts point to the existence of differentiated biochemical adaptations and acclimations to low temperature
in polar plankton, an issue that has been much discussed in the recent past.
Received: 20 July 1995/Accepted: 28 October 1995 相似文献
14.
Meenakshi Banerjee R. Craig Everroad Richard W. Castenholz 《Extremophiles : life under extreme conditions》2009,13(4):707-716
Cyanobacteria that grow above seawater salinity at temperatures above 45°C have rarely been studied. Cyanobacteria of this
type of thermo-halophilic extremophile were isolated from siliceous crusts at 40–45°C in a geothermal seawater lagoon in southwest
Iceland. Iceland Clone 2e, a Leptolyngbya morphotype, was selected for further study. This culture grew only at 45–50°C, in medium ranging from 28 to 94 g L−1 TDS, It showed 3 doublings 24 h−1 under continuous illumination. This rate at 54°C was somewhat reduced, and death occurred at 58°C. A comparison of the 16S
rDNA sequence with all others in the NCBI database revealed 2 related Leptolyngbya isolates from a Greenland hot spring (13–16 g L−1 TDS). Three other similar sequences were from Leptolyngbya isolates from dry, endolithic habitats in Yellowstone National Park. All 6 formed a phylogenetic clade, suggesting common
ancestry. These strains shared many similarities to Iceland Clone 2e with respect to temperature and salinity ranges and optima. Two endolithic Leptolyngbya isolates, grown previously at 23°C in freshwater medium, grew well at 50°C but only in saline medium. This study shows that
limited genotypic similarity may reveal some salient phenotypic similarities, even when the related cyanobacteria are from
vastly different and remote habitats. 相似文献
15.
Effects of elevated temperature on bacterial community structure and function in bioreactors treating a synthetic wastewater 总被引:1,自引:0,他引:1
T M LaPara A Konopka C H Nakatsu J E Alleman 《Journal of industrial microbiology & biotechnology》2000,24(2):140-145
The impact of elevated temperature on bacterial community structure and function during aerobic biological wastewater treatment
was investigated. Continuous cultures, fed a complex growth medium containing gelatin and α-lactose as the principal carbon
and energy sources, supported mixed bacterial consortia at temperatures ranging from 25–65°C. These temperature- and substrate-acclimated
organisms were then used as inocula for batch growth experiments in which the kinetics of microbial growth and substrate utilization,
efficiency of substrate removal, and mechanism of substrate removal were compared as functions of temperature. Bacterial community
analysis by denaturing gradient gel electrophoresis (DGGE) revealed that distinct bacterial consortia were supported at each
temperature. The efficiency of substrate removal declined at elevated temperatures. Maximum specific growth rates and the
growth yield increased with temperature from 25–45°C, but then decreased with further elevations in temperature. Thus, maximum
specific substrate utilization rates did not vary significantly over the 40°C temperature range (0.64 ± 0.04 mg COD mg−1 dry cell mass h−1). A comparison of the degradation of the protein and carbohydrate portions of the feed medium revealed a lag in α-lactose
uptake at 55°C, whereas both components were utilized simultaneously at 25°C. Journal of Industrial Microbiology & Biotechnology (2000) 24, 140–145.
Received 09 August 1999/ Accepted in revised form 12 November 1999 相似文献
16.
We aimed to assess the potential effects of fumigation by methyl salicylate (MeSA) on plant monoterpene production and emissions.
We evaluated monoterpene production and emissions both by chromatographic and proton transfer reaction mass spectrometry at
the whole plant-and leaf-scales, in MeSa-fumigated (ca. 60 mm3 m−3 in air) and control (without MeSa fumigation) holm oak (Quercus ilex L.) plants exposed to temperatures ranging from 25 to 50 °C. The MeSa-fumigated plants showed ca. 3–4-fold greater leaf monoterpene concentrations and emission rates than the control plants between the temperatures of 25
to 45 °C. 相似文献
17.
Linking isoprene with plant thermotolerance, antioxidants and monoterpene emissions 总被引:10,自引:1,他引:10
The purpose of the present study was to test the possible plant thermotolerance role of isoprene and to study its relationship with non-enzymatic antioxidants and terpene emissions. The gas exchange, chlorophyll fluorescence, extent of photo- and oxidative stress, leaf damage, mechanisms of photo- and antioxidant protection, and terpene emission were measured in leaves of Quercus ilex seedlings exposed to a ramp of temperatures of 5 °C steps from 25 to 50 °C growing with and without isoprene (10 µL L−1) fumigation. The results showed that isoprene actually conferred thermotolerance (shifted the decrease of net photosynthetic rates from 35 to 45 °C, increased Fv/Fm at 50 °C from 0.38 to 0.65, and decreased the leaf area damaged from 27 to 15%), that it precluded or delayed the enhancement of the antioxidant non-enzymatic defence conferred by α-tocopherol, ascorbic acid or β-carotene consumption in response to increasing temperatures, and that it decreased by approximately 70% the emissions of monoterpenes at the highest temperatures. This suggests that there are inducible mechanisms triggered by the initial stages of thermal damage that up-regulate these antioxidant compounds at high temperatures and that these mechanisms are somehow suppressed in the presence of exogenous isoprene, which seems to already exert an antioxidant-like behaviour. 相似文献
18.
Polar-desert plants experience low average air temperatures during their short growing season (4–8 °C mean July temperature).
In addition, low availability of inorganic nitrogen in the soil may also limit plant growth. Our goals were to elucidate which
N sources can be acquired by polar-desert plants, and how growth and N-uptake are affected by low growth temperatures. We
compared rates of N-uptake and increases in mass and leaf area of two polar-desert species (Cerastium alpinum L. and Saxifraga caespitosa L.) over a period of 3 weeks when grown at two temperatures (6 °C vs. 15 °C) and supplied with either glycine, NH4
+ or NO3
−. At 15 °C, plants at least doubled their leaf area, whereas there was no change in leaf area at 6 °C. Measured mean N-uptake
rates varied between 0.5 nmol g−1 root DM s−1 on glycine at 15 °C and 7.5 nmol g−1 root DM s−1 on NH4
+ at 15 °C. Uptake rates based upon increases in mass and tissue N concentrations showed that plants had a lower N-uptake rate
at 6 °C, regardless of N source or species. We conclude that these polar-desert plants can use all three N sources to increase
their leaf area and support flowering when grown at 15 °C. Based upon short-term (8 h) uptake experiments, we also conclude
that the short-term capacity to take up inorganic or organic N is not reduced by low temperature (6 °C). However, net N-uptake
integrated over a three-week period is severely reduced at 6 °C.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
19.
Jeong Seok Oh Hee Ho Park Tai Hyun Park 《Biotechnology and Bioprocess Engineering》2008,13(4):470-475
In a two-phase operation, E. coli containing λSNNU1 (Q
−
S
−) in the chromosome is typically cultured at 33°C and cloned gene expression is induced by elevating the temperature. At least
40°C is necessary for complete induction of cloned gene expression; however, temperatures above 40°C have been shown to inhibit
cloned gene expression. This suggests that a three-phase operation, which has an induction phase between the growth and production
phases, may result in higher gene expression. In this study, optimal temperature management strategies were investigated for
the three-phase operation of cloned gene expression in thermally inducible E. coli/bacteriophage systems. The optimal temperature for the induction phase was determined to be 40°C. When the temperature of
the production stage was 33°C, the optimal time period for the induction phase at 40°C was determined to be 60 min. In contrast,
when the temperature of the production phase was 37°C, the optimal period for the induction phase at 40°C was 20∼30 min. When
the three-phase temperature and temporal profile were set at a growth phase of 33°C, an induction phase at 40°C for 30 min,
and a production phase at 37°C, the highest level of cloned gene expression was achieved. 相似文献
20.
Root exudate components change litter decomposition in a simulated rhizosphere depending on temperature 总被引:3,自引:0,他引:3
The release of root exudates into the rhizosphere is known to enhance soil biological activity and alter microbial community structure. To assess whether root exudates also stimulated litter decomposition, in a rhizosphere model system we continuously injected solutions of glucose, malate or glutamate through porous Rhizon® soil solution samplers into the soil at rhizosphere concentrations. The effect of these substances on the decomposition of 14C-labelled Lolium perenne shoot residues present in the soil was evaluated by monitoring 14CO2 evolution at either 15°C or 25°C. The incorporation of the 14C into the microbial biomass and appearance in the dissolved organic matter (DOM) pool was estimated after 32 d incubation. The presence of malate and glutamate increased the mineralization of L. perenne residues by approximately 20% relative to the soil without their addition at 15°C, however, no significant effects on residue decomposition were observed at 25°C. The incorporation of the 14C-label into the microbial biomass and DOM pool was not affected by the addition of either glucose, malate or glutamate. Although nearly the same amount of L. perenne residues were mineralized at either temperature after 32 d, less 14C was recovered in the microbial biomass and DOM pools at 25°C compared to 15°C. Alongside other results, this suggests that the rate of microbial turnover is greater at 25°C compared to 15°C. We conclude that the addition of labile root exudate components to the rhizosphere induced a small but significant increase on litter decomposition but that the magnitude of this effect was regulated by temperature. 相似文献