Phospholipid Fatty Acid Pattern Research Articles

Assessing the effects of Cu and pH on microorganisms in highly acidic vineyard soils

Because of the use of agricultural land for wine production and the frequent use of copper (Cu)‐based fungicides, Cu concentration has been increasing in soils in many parts of the world. In vineyards with acid parent materials, low soil pH may also encourage Cu toxicity, but it is common to use lime in order to increase the soil pH and improve crop yields. Thus, vineyard soils may have large variations in pH, which will affect the microbial communities, making it difficult to isolate possible toxic effects of Cu on soil microbes. Here, analyses of phospholipid fatty acid (PLFA) patterns and pollution‐induced community tolerance (PICT, using leucine incorporation) were used to study the effect of Cu accumulation at small to medium concentrations in acid soils (pH 4.0–5.8) in vineyards with different land‐use history (young, old and abandoned vineyards). The results suggested that soil pH played a dominant role in determining the composition of the microbial community of the soils. Only a small effect of soil Cu could be detected and the effect on microbial community composition was much less than the pH effect. PICT analysis suggested that bacterial communities in old vineyards were more tolerant of Cu than those in the abandoned vineyards. However, increased PICT (Cu tolerance of the bacterial community) was not directly correlated with Cu concentration in the soils. Instead, the estimated Cu tolerance was significantly correlated with soil pH.

Incorporation of 13C-labelled rice rhizodeposition carbon into soil microbial communities under different water status

The overall processes by which carbon is fixed by plants in photosynthesis then released into the soil by rhizodeposition and subsequently utilized by soil micro-organisms, links the atmospheric and soil carbon pools. The objective of this study was to determine the plant derived 13C incorporated into the phospholipid fatty acid (PLFA) pattern in paddy soil, to test whether utilization of rice rhizodeposition carbon by soil micro-organisms is affected by soil water status. This is essential to understand the importance of flooded conditions in regulating soil microbial community structure and activity in wetland rice systems. Rice plants were grown in soil derived from a paddy system under controlled irrigation (CI), or with continuous waterlogging (CW). Most of the 13C-labelled rice rhizodeposition carbon was distributed into the PLFAs 16:0, 18:1ω7 and 18:1ω9 in both the CW and CI treatments. The bacterial PLFAs i15:0 and a15:0, both indicative of gram positive bacteria, were relatively more abundant in the treatments without rice plants. When rice plants were present rates of 13C-incorporation into i15:0 and a15:0 was slow; the microbes containing these PLFAs may derive most of their carbon from more recalcitrant C (soil organic matter). PLFAs, 18:1ω7 and 16:1ω7c, indicative of gram negative bacteria showed a greater amount incorporation of labelled plant derived carbon in the CW treatment. In contrast, 18:2ω6,9 indicative of fungi and 18:1ω9 indicative of aerobes but also potentially fungi and plant roots had greater incorporation in the CI treatment. The greater root mass concomitant with lower incorporation of 13C into the total PLFA pool in the CW treatment suggests that the microbial communities in wetland rice soil are limited by factors other than substrate availability in flooded conditions. In this study differing soil microbial communities were established through manipulating the water status of paddy soils. Steady state 13C labelling enabled us to determine that the microbial community utilizing plant derived carbon was also affected by water status.

Rhizosphere isoflavones (daidzein and genistein) levels and their relation to the microbial community structure of mono-cropped soybean soil in field and controlled conditions

Despite an increase in the understanding of the soybean isoflavones involved in root-colonizing symbioses, relatively little is known about their levels in the rhizosphere and their interactions with the soil microbial community. Based on a 13-year experiment of continuous soybean monocultures, in the present study we quantified isoflavones in the soybean rhizosphere and analyzed the soil microbial community structure by examining its phospholipid fatty acid (PLFA) profile. Two isoflavones, daidzein (7, 4′-dihydroxyisoflavone) and genistein (5,7,4′- trihydroxyisoflavone), were detected in the rhizosphere soil of soybean plants, with the concentrations in the field varying with duration of mono-cropping. Genistein concentrations ranged from 0.4 to 1.2 μg g −1 dry soil over different years, while daidzein concentrations rarely exceeded 0.6 μg g −1 dry soil. PLFA profiling showed that the signature lipid biomarkers of bacteria and fungi varied throughout the years of the study, particularly in mono-cropping year 2, and mono-cropping years 6–8. Principal component analysis clearly identified differences in the composition of PLFA during different years under mono-cropping. There was a positive correlation between the daidzein concentrations and soil fungi, whereas the genistein concentration showed a correlation with the total PLFA, fungi, bacteria, Gram (+) bacteria and aerobic bacteria in the soil microbial community. Both isoflavones were easily degraded in soil, resulting in short half-lives. Concentrations as small as 1 μg g −1 dry soil were sufficient to elicit changes in microbial community structure. A discriminant analysis of PLFA patterns showed that changes in microbial community structures were induced by both the addition of daidzein or genistein and incubation time. We conclude that daidzein and genistein released into the soybean rhizosphere may act as allelochemicals in the interactions between root and soil microbial community in a long-term mono-cropped soybean field.

Effects of soil frost on growth, composition and respiration of the soil microbial decomposer community

Most climate change scenarios predict that the variability of weather conditions will increase in coming decades. Hence, the frequency and intensity of freeze-thaw cycles in high-latitude regions are likely to increase, with concomitant effect on soil carbon biogeochemistry and associated microbial processes. To address this issue we sampled riparian soil from a Swedish boreal forest and applied treatments with variations in four factors related to soil freezing (temperature, treatment duration, soil water content and frequency of freeze-thaw cycles), at three levels in a laboratory experiment, using a Central Composite Face-centred (CCF) experimental design. We then measured bacterial (leucine incorporation) and fungal (acetate in ergosterol incorporation) growth, basal respiration, soil microbial phospholipid fatty acid (PLFA) composition, and concentration of dissolved organic carbon (DOC). Fungal growth was higher in soil exposed to freeze-thawing perturbations and freezing temperatures of −6 °C and −12 °C, than under more constant conditions (steady 0 °C). The opposite pattern was found for bacteria, resulting in an increasing fungal-to-bacterial growth ratio following more intensive winter conditions. Soil respiration increased with water content, decreased with treatment duration and appeared to mainly be driven by treatment-induced changes in the DOC concentration. There was a clear shift in the PLFA composition at 0 °C, compared with the two lower temperatures, with PLFA markers associated with fungi as well as a number of unsaturated PLFAs being relatively more common at 0 °C. Shifts in the PLFA pattern were consistent with those expected for phenotypic plasticity of the cell membrane to low temperatures. There were small declines in PLFA concentrations after freeze-thawing and with longer durations. However, the number of freeze-thaw events had no effect on the microbiological variables. The findings suggest that the higher frequency of freeze-thaw events predicted to follow the global warming will likely have a limited impact on soil microorganisms.

A grape polyphenol extract modulates muscle membrane fatty acid composition and lipid metabolism in high-fat–high-sucrose diet-fed rats

Accumulation of muscle TAG content and modification of muscle phospholipid fatty acid pattern may have an impact on lipid metabolism, increasing the risk of developing diabetes. Some polyphenols have been reported to modulate lipid metabolism, in particular those issued from red grapes. The present study was designed to determine whether a grape polyphenol extract (PPE) modulates skeletal muscle TAG content and phospholipid fatty acid composition in high-fat-high-sucrose (HFHS) diet-fed rats. Muscle plasmalemmal and mitochondrial fatty acid transporters, GLUT4 and lipid metabolism pathways were also explored. The PPE decreased muscle TAG content in HFHS/PPE diet-fed rats compared with HFHS diet-fed rats and induced higher proportions of n-3 PUFA in phospholipids. The PPE significantly up-regulated GLUT4 mRNA expression. Gene and protein expression of muscle fatty acid transporter cluster of differentiation 36 (CD36) was increased in HFHS diet-fed rats but returned to control values in HFHS/PPE diet-fed rats. Carnitine palmitoyltransferase 1 protein expression was decreased with the PPE. Mitochondrial β-hydroxyacyl CoA dehydrogenase was increased in HFHS diet-fed rats and returned to control values with PPE supplementation. Lipogenesis, mitochondrial biogenesis and mitochondrial activity were not affected by the PPE. In conclusion, the PPE modulated membrane phospholipid fatty acid composition and decreased muscle TAG content in HFHS diet-fed rats. The PPE lowered CD36 gene and protein expression, probably decreasing fatty acid transport and lipid accumulation within skeletal muscle, and increased muscle GLUT4 expression. These effects of the PPE are in favour of a better insulin sensibility.

Biochemical properties and microbial community structure of five different soils after atrazine addition

Atrazine is one of the most used herbicides worldwide; however, consequences of its long-term agricultural use are still unknown. A laboratory study was performed to examine changes in microbial properties following ethylamino-N-15-atrazine addition, at recommended agronomic dose, to five acidic soils from Galicia (NW Spain) showing different physico-chemical characteristics, as well as atrazine application history. Net N mineralization was observed in all soils, with nitrate being the predominant substance formed. The highest values were detected in soils with low atrazine application history. From 2% to 23% of the atrazine-N-15 was found in the soil inorganic-N pool, the highest values being detected after 9 weeks in soils with longer atrazine application history and lower indigenous soil N mineralization. The application of atrazine slightly reduced the amount of soil N mineralized and microbial biomass at short term. Soluble carbohydrates and beta-glucosidase and urease activity decreased with incubation time, but were not significantly affected by the single application of atrazine. Microbial community structure changed as consequence of both soil type and incubation time, but no changes in the phospholipid fatty acid (PLFA) pattern were detected due to recent atrazine addition at normal doses. The saturated 17- to 20-carbon fatty acids had higher relative abundance in soils with a longer atrazine history and fungal biomass, as indicated by the PLFA 18:2 omega 6,9, decreased with the incubation time. The results suggested that the PLFA pattern and soil N dynamics can detect the long-term impact of repeated atrazine application to agricultural soils.

Soil microbial recolonisation after a fire in a Mediterranean forest

The capacity of different microbial groups to recolonise soil after a fire event will be decisive in determining the microbial community after the fire. Microbial recovery after a wildfire that occurred in Sierra la Grana (Alicante province, southeast Spain) was tracked for 32 months after the fire. Colony forming units (CFUs) of different microbial groups, microbial biomass, soil respiration, bacterial growth (leucine incorporation) and changes in the microbial community structure (phospholipid fatty acid (PLFA) analysis) were determined directly after the fire and four times during the recovery period. Direct effects were reflected by low values of most microbiological variables measured immediately after the fire. Microbial biomass increased during the first year after the fire but was below the unburned reference site 32 months after the fire. Bacterial activity and soil respiration showed the highest values immediately after the fire, but decreased to values similar to that of the unburned reference site or even lower (respiration) 32 months after the fire. Colony forming units of bacterial groups estimated by the plate count method peaked 8 months after the fire, but then decreased, showing values similar to the unburned reference site at the end of the study, with the exception of spore formers, which were 20 times higher than the reference site 32 months after the fire. Fungal CFUs were more sensitive to the fire and recovered more slowly than bacteria. Fungi recovering less rapidly than bacteria were also indicated by the PLFA pattern, with PLFAs indicative of fungi being less common after the fire. The recovery of microbial biomass and activity was mirrored by the initially very high levels of dissolved organic carbon being consumed and decreasing within 8 months after the fire. The wildfire event had thus resulted in a decrease in microbial biomass, with a more bacteria-dominated microbial community.

Use and misuse of PLFA measurements in soils

The determination of the phospholipid fatty acid (PLFA) pattern of soil organisms has become one of the most commonly used methods to study microbial community structure. Here we recapitulate the background of our work applying the PLFA method to soil in the early 1990s. We also stress that although the PLFA method was, and still is, a rapid and sensitive method to detect changes in the microbial community in soil, as with all popular methods it can be misused. We discuss problems in PLFA interpretation, the extent of turn-over of PLFAs in soil, and the flawed use of diversity indices to evaluate PLFA patterns.

The microbial community composition changes rapidly in the early stages of decomposition of wheat residue

Abstract It is generally accepted that during the early stages of residue decomposition, easily available compounds are decomposed, leading to a relative increase in more recalcitrant compounds in the later stages of decomposition and that these changes in substrate availability are associated with changes in microbial community composition. However most studies on residue decomposition are conducted over several weeks or months; little is known about the changes in microbial community composition in the first weeks of decomposition. To address this knowledge gap, we incubated wheat residues inoculated with a microbial suspension in mesh bags buried in sand for 30 days, with sampling on days 0, 2, 4, 6, 8, 10, 15, 20, 25 and 30. Of the C added with the residues, 10, 18 and 25% had been respired on days 10, 20 and 30, respectively. The sum of PLFAs (phospholipid fatty acids), as an indicator of microbial biomass, increased strongly in the first 4 days and then decreased. The concentration of bacterial fatty acids was maximal on days 2 and 4, whereas the concentration of fungal fatty acids peaked on day 15. Microbial community composition (based on PLFA patterns) changed rapidly, with significant changes in the first 8 days and from day 8 to day 20. There were no significant changes in microbial community composition after day 20. The concentration of water-soluble C decreased strongly in the first 8 days, suggesting that the rapid changes in microbial community in this period are related to the changes in water-soluble C. Residue C chemistry, assessed by 13C NMR spectroscopy, changed little during the incubation period. This study showed that microbial community composition in decomposing residues changes rapidly in the first 1–2 weeks, which is, at least partly, the result of competition for the easily available compounds in the water-soluble fraction. After depletion of the water-soluble compounds, the microbial community composition changes more slowly.

2,4-Dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA) and 6-Methoxy-benzoxazolin-2-one (MBOA) Levels in the Wheat Rhizosphere and Their Effect on the Soil Microbial Community Structure

Despite increasing knowledge of 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA) and 6-methoxy-benzoxazolin-2-one (MBOA) as allelochemicals involved in the defense of wheat against pests, relatively little is known about their levels in the rhizosphere and interactions with the soil microbial community. This study quantified DIMBOA and MBOA in the wheat rhizosphere and analyzed the soil microbial community structure. MBOA rather than DIMBAO was found in the wheat rhizosphere, and its concentration varied with cultivars, plant densities, and growth conditions. Wheat could detect the presence of competing weeds and respond by increased MBOA in the rhizosphere. There was a linear positive relationship between the MBOA level in the wheat rhizosphere and soil fungi/bacteria. When DIMBOA was applied to soil, yielding MBOA increased soil fungi. There were different phospholipid fatty acid (PLFA) patterns in soil incubated with DIMBOA and MBOA. These results suggested that DIMBOA and MBOA could affect the soil microbial community structure to their advantage through the change in fungi populations.

Effects of sulfadiazine-contaminated fresh and stored manure on a soil microbial community

The response of soil microorganisms to manure contaminated by veterinary antibiotics is not well understood. Therefore, a 57-d incubation experiment was performed to investigate effects of sulfadiazine (SDZ) contaminated manure on soil microorganisms. Manure was either obtained directly from medicated pigs or subsequently stored for six month. We hypothesized that SDZ-contaminated manure changes functions and structural composition of soil microorganisms and that manure storage reduces antibiotic effects. Rates of potential nitrification and N mineralization as well as PLFA (phospholipid fatty acid) patterns were determined. Addition of uncontaminated manure to soil affected N cycle processes and the microbial community structure, and effects differed between fresh and stored manure. The rates of potential nitrification, ammonification and N mineralization and ratios of bacteria/fungi and gram-negative/gram-positive bacteria derived from PLFA were lower in soil treated with stored compared to fresh, uncontaminated manure. SDZ-contaminated manure affected N cycle processes with slight differences due to manure storage, whereas PLFA tot and the derived bacteria/fungi ratio were only reduced by stored, contaminated manure. SDZ reduced rates of nitrification and N mineralization, while ammonification increased. Effects of SDZ on soil microorganisms were significant although the bioavailable SDZ fraction (CaCl 2-extractable) rapidly declined. We conclude that conventional manure storage is unsuited to reduce risks from sulfonamide antibiotics in the soil environment.

Influence of benomyl and prometryn on the soil microbial activities and community structures in pasture grasslands of Slovakia

The effects of pesticides (a herbicide and a fungicide) on the microbial community structure and their activity were analyzed in soil from four alpine pasture grasslands in Slovakia. Specifically, the effects of the herbicide, Gesagard (prometryn active ingredient), and fungicide, Fundazol 50 WP (benomyl active ingredient), on the microbial respiration activity (CO2 production), the numbers of selective microbial physiological groups (CFU.g−1) and the structure (relative abundance) of soil microbial communities [(phospholipid fatty acid (PLFA)] were analyzed under controlled laboratory conditions. All treatments including the treatments with pesticides increased (statistically significantly) the production of CO2 in all fields during 21 days of incubation and posed a statistically insignificant negative influence on the numbers of the observed physiological groups of microorganisms. The significantly negative influence was evaluated only in the numbers of two physiological groups; spores of bacteria utilizing organic nitrogen and bacteria, and their spores utilizing inorganic nitrogen. A shift in the microbial composition was evident when the PLFA patterns of samples from different sites and treatments were compared by the Principal Component Analysis (PCA). According to the second component PCA 2 (15.95 %) the locations were grouped into two clusters. The first one involved the Donovaly and Dubakovo sites and the second one contained the Velka Fatra and Mala Fatra locations. The PLFA composition of the soils showed important changes after the treatment with pesticides according to PCA 1 (66.06 %). Other treatments had not had a significant effect on the soil microbial community with the exception of the population of fungi. The lower relative abundance (significant effect) of Gram-positive bacteria, actinomycetes and general group of bacteria were determined in samples treated by the herbicide Gesagard. The application of fungicide Fundazol decreased (statistically significantly) the relative abundance of actinomycetes and general group of bacteria and paradoxically increased the population of fungi.

Microbial community structure of vineyard soils with different pH and copper content

The phospholipid fatty acid (PLFA) pattern of vineyard soils from the Northwest of the Iberian Peninsula was studied to identify soil factors determining the microbial community structure, with special emphasis on effects of Cu pollution and pH. A wide range of soil samples, collected from six winegrowing regions (Rías Baixas, Ribeiro, Ribeira Sacra, Monterrei, Valdeorras and Vinhos Verdes) was analyzed. Physico-chemical properties, including total Cu content, five different Cu fractions and available Cu, were also determined. Total Cu varied between 33 and 1120 mg kg −1 and pH water between 4.3 and 7.3. Soil pH rather than Cu content was most important in determining the composition of the microbial community. An increase in the relative concentrations of the monounsaturated PLFAs 16:1ω5, 16:1ω7c, 17:1ω8 and 18:1ω7 and a decrease of br18:0, i17:0, 17:0 and cy19:0 was correlated to an increase in pH. A significant effect of Cu was also found, with an increase in the branched fatty acids 10Me17:0, i16:0, 10Me18:0, a17:0 and br17:0 as consequence of Cu pollution. This change in the PLFA pattern was correlated to both the total and available fractions of Cu. Although the PLFA pattern was a useful tool to assess factors affecting the microbial composition, it is difficult to differentiate between these factors.

Responses of nitrogen transformation and microbial community composition to nitrogen enrichment patch

Fertilization produces many nutrient patches that have been confirmed to affect root growth. However, it is not clear how nutrient transformation and microbial community composition are affected in an inorganic nutrient patch. In this experiment, a nitrogen enrichment patch was formed by the diffusion of a urea fertilizer layer in a specially-designed container. Responses of nitrogen transformation and microbial community composition to the nitrogen enrichment patch were investigated at different incubation times. Results showed that nitrogen status and microbial community composition were slightly affected in the control patch (CK patch). In the nitrogen enrichment patch, however, soil pH was significantly increased in most soil layers close to the urea fertilizer layer; NO2−–N was the predominant form of mineral N, and its transformation to NO3−–N was delayed. Microbial community composition shifted significantly, especially before day 28 of incubation. Principal components analysis (PCA) of phospholipid fatty acids (PLFAs) patterns showed that the microbial community presented different sensitivity to high nitrogen concentration. Fungi (18:2ω6,9) showed the least sensitivity to high concentrations of NO2−–N and NO3−–N. Gram-positive bacteria showed the most sensitivity to NO2−–N. Gram-negative bacteria (cy17:0, cy19:0, 18:1ω9, and 18:1ω7) and actinomycetes (10Me17:0 and 10Me18:0) presented similar responses to NO2−–N and NO3−–N. Results of this study indicate that changes in nitrogen transformation and microbial community composition are likely to occur in nitrogen enrichment patches, but the extent of those changes depend on the microbial species and the distance of soil layers from the urea layer.

The impact of farming practice on soil microorganisms and arbuscular mycorrhizal fungi: Crop type versus long-term mineral and organic fertilization

This study investigates an arable field soil with long-term (27 and 28 years) mineral (NPK) and organic (cattle manure, cattle manure with biodynamic preparations) fertilizer amendments at low, medium and high amounts. Arbuscular mycorrhizal (AM) fungi host plant wheat was cultivated in the first vegetation period and non-host amaranth in the second. Phospholipid fatty acids (PLFA) were used to assess soil microbial biomass and community structure. AM fungi were quantified using the marker fatty acid 16:1ω5, with its occurrence in soil PLFAs representing hyphae and in neutral lipid fatty acid (NLFA) spores. Soil microbial biomass was enhanced by the addition of manure and at higher amounts for both fertilizers. AM fungal hyphae and spore biomass responded positively to manure application. The soil microbial community under both crops was dominated by bacteria. The ratio of fungal to bacterial (f/b) PLFAs increased with higher fertilizer amounts but decreased in amaranth plots with the application of manure. Meanwhile the ratio of Gram+/Gram− bacteria indicating environmental conditions (e.g. pH, temperature) was higher in amaranth plots with the addition of manure as compared to wheat plots. Soil PLFA revealed distinct effect of crop type displayed by changes in the occurrence of saturated fatty acids and biomarkers for Gram-negative bacteria and saprotrophic fungi. The latter additionally accounted for the dissimilarity between fertilizer treatments. In sum, the soil PLFA pattern distinctively separated wheat from amaranth plots at 0–5 cm soil depth, indicating a stronger effect of crop rotation and crop identity on soil microorganisms than long-term fertilizer practice.

Nitrifier denitrification can be a source of N2O from soil: a revised approach to the dual‐isotope labelling method

Nitrifier denitrification (i.e. nitrite reduction by ammonia oxidizers) is one of the biochemical pathways of nitrous oxide (N2O) production. It is increasingly suggested that this pathway may contribute substantially to N2O production in soil, the major source of this greenhouse gas. However, although monoculture studies recognize its potential, methodological drawbacks prohibit conclusive proof that nitrifier denitrification occurs in actual soils. Here we suggest and apply a new isotopic approach to identify its presence in soil. In incubation experiments with 12 soils, N2O production was studied using oxygen (O) and nitrogen (N) isotope tracing, accounting for O exchange. Microbial biomass C and N and phospholipid fatty acid (PLFA) patterns were analysed to explain potential differences in N2O production pathways. We found that in at least five of the soils nitrifier denitrification must have contributed to N2O production. Moreover, it may even have been responsible for all NH4+‐derived N2O in most soils. In contrast, N2O as a by‐product of ammonia oxidation contributed very little to total production. Microbial biomass C and N and PLFA‐distinguished microbial community composition were not indicative of differences in N2O production pathways. Overall, we show that combined O and N isotope tracing may still provide a powerful tool to understand N2O production pathways, provided that O exchange is accounted for. We conclude that nitrifier denitrification can indeed occur in soils, and may in fact be responsible for the greater proportion of total nitrifier‐induced N2O production.

Impact of imazethapyr on the microbial community structure in agricultural soils

Large amounts of imazethapyr were applied for weed control in cultivation fields in China, but their effects on the soil microbial community remains unclear. In this study, two agricultural soils, a silty loam (HS) and a loamy soil (QL), were spiked with imazethapyr (CK, 0.1, 1 and 10 mg kg −1) and incubated for 1, 15, 30, 60, 90 and 120 d. In addition, untreated controls received only water. The soil microbial community structures were characterized by investigating the phospholipid fatty acids (PLFA) and microbial biomass C. Soil microbial biomass C and total concentration of PLFA were variable with incubation time, which were also reduced by the addition of imazethapyr. Imazethapyr addition also decreased the ratios of GN/GP and fungi/bacteria. A larger stress level, measured as the ratio of PLFA (cyc17:0 + cyc19:0)/(16:1 ω7c + 18:1 ω7c), was found in the high concentration (1 and 10 mg kg −1) herbicide treatment groups. The effects of imazethapyr at the field application on soil microbial biomass and microbial community were minor. Principal component analysis (PCA) of the PLFA clearly separated the treatments and incubation times. Both soils showed different total PLFA concentrations and ratios of GN/GP and fungi/bacteria, but similar changes in the PLFA pattern upon soil treatment. The soil microbial community structure was shifted by the addition of imazethapyr, which recovered after 60 d. In addition, the dissipation of imazethapyr was slow in both soils. Our results demonstrated that the addition of imazethapyr shifted the microbial community structure, but that it recovered after a period of incubation.

Supplementation With Fatty Acids Influences the Airway Nitric Oxide and Inflammatory Markers in Patients With Cystic Fibrosis

To obtain a balance in the fatty acid (FA) metabolism is important for the inflammatory response and of special importance in cystic fibrosis (CF), which is characterized by impaired FA metabolism, chronic inflammation, and infection in the airways. Nitric oxide (NO) has antimicrobial properties and low nasal (nNO) and exhaled NO (FENO), commonly reported in CF that may affect bacterial status. The present study investigates the effect of different FA blends on nNO and FENO and immunological markers in patients with CF. Forty-three patients with CF and "severe" mutations were consecutively enrolled in a randomized double-blind placebo-controlled study with 3 FA blends containing mainly n-3 or n-6 FA or saturated FA acting as placebo. FENO, nNO, serum phospholipid concentrations of FA, and biomarkers of inflammation were measured before and after 3 months of supplementation. Thirty-five patients in clinically stable condition completed the study. The serum phospholipid FA pattern changed significantly in all 3 groups. An increase of the n-6 FA, arachidonic acid, was associated with a decrease of FENO and nNO. The inflammatory biomarkers, erythrocyte sedimentation rate, and interleukin-8 decreased after supplementation with n-3 FA and erythrocyte sedimentation rate increased after supplementation with n-6 FA. This small pilot study indicated that the composition of dietary n-3 and n-6 FA influenced the inflammatory markers in CF. FENO and nNO were influenced by changes in the arachidonic acid concentration, supporting previous studies suggesting that both the lipid abnormality and the colonization with Pseudomonas influenced NO in the airways.

Functional microbial community response to nutrient pulses by artificial groundwater recharge practice in surface soils and subsoils

Subsurface microorganisms are essential constituents of the soil purification processes associated with groundwater quality. In particular, soil enzyme activity determines the biodegradation of organic compounds passing through the soil profile. Transects from surface soil to a depth of 3.5 m were investigated for microbial and chemical soil characteristics at two groundwater recharge sites and one control site. The functional diversity of the microbial community was analyzed via the activity of eight enzymes. Acid phosphomonoesterase was dominant across sites and depths, followed by L-leucine aminopeptidase and beta-glucosidase. Structural [e.g. phospholipid fatty acid (PLFA) pattern] and functional microbial diversities were linked to each other at the nonwatered site, whereas amendment with nutrients (DOC, NO(3)(-)) by flooding uncoupled this relationship. Microbial biomass did not differ between sites, whereas microbial respiration was the highest at the watered sites. Hence, excess nutrients available due to artificial groundwater recharge could not compensate for the limitation by others (e.g. phosphorus as assigned by acid phosphomonoesterase activity). Instead, at a similar microbial biomass, waste respiration via overflow metabolism occurred. In summary, ample supply of carbon by flooding led to a separation of decomposition and microbial growth, which may play an important role in regulating purification processes during groundwater recharge.

Allantoin-induced changes of microbial diversity and community in rice soil

Rice (Oryza sativa L.) may release allantoin into paddy soil. Currently, little attention has been paid to the effects of allantoin on soil microbial diversity and community. In this study, the diversity indices for the microbial community in rice soil and the allantoin-induced shifts in the microbial community composition across moisture regimes versus incubation times were examined by looking at phospholipid fatty acid (PLFA) profiles and PCR-denaturing gradient gel electrophoresis (DGGE) patterns. The total PLFA concentration increased with the amount of allantoin applied during incubation. A similar trend occurred for microbial biomass carbon (MBC) and pH. Furthermore, applying allantoin resulted in an increased ratio of anaerobe: aerobe and bacteria: fungi but decreased the ratio of Gram-negative bacteria: Gram-positive bacteria (GN: GP) and fungal marker 18:2ω6,9c under flooded rice soil. A stepwise discriminant analysis of the PLFA pattern clearly separated allantoin-treated samples from non-treated samples. There was also a clear split between different incubation times. Moisture treatments differed in the ratios of anaerobe: aerobe and GN: GP but showed similar trends in total PLFA concentrations and the bacteria: fungi ratio during incubation. These results suggest that application of allantoin stimulates shifts in microbial community composition and increases microbial diversity as well as living microbial biomass in rice soil.