Amino Sugar Content Research Articles

Amino sugars in arctic soils

Amino sugars in soils are assumed to be of microbial origin. Their levels in soil, can provide insights into the microbial contribution to soil organic matter (SOM) and might serve as an indicator of SOM quality. Four amino sugars, glucosamine, galactosamine, mannosamine, and muramic acid were determined by gas chromatography in five soils from the tundra Alaska before and after incubation for 4 months at 4 and 25°C. Glucosamine and muramic acid analyses were utilized to represent fungal biomass and bacterial biomass, respectively. Total amino sugar N represented 0.8 to 3.3% of the total soil N in these five tundra soils, and the proportion of soil N as amino sugars increased with depth. Total amino sugar and fungal glucosamine N increased or remained constant during incubation at 4 and 25°C (except site 3 Cf horizon which decreased after incubation at 4°C), suggesting that total microbial biomass and fungal biomass increased. Bacterial biomass had an increase after incubation at 4°C, and a relative decrease at 25°C (except for Cf horizon). Fungal glucosamine to muramic acid ratios demonstrated that fungal biomass increased faster than bacterial biomass at 25°C, and slower at 4°C, indicating that at higher temperature, fungi dominated the microbial biomass in the soils studied. The mechanisms involved in the accumulation and decomposition of amino sugars in soil during incubation were not clear. No correlations were observed between the amino sugar contents and CO2 evolution during incubation, indicating that amino sugar abundance may not be an indicator of the bioavailability of SOM in soils. However, they can provide insights into the microbial contribution to SOM.

Fate of microbial residues in sandy soils of the South African Highveld as influenced by prolonged arable cropping

SummaryLong‐term cultivation of former grassland soils results in a significant decline of both living and dead microbial biomass. We evaluated the effect of duration of cropping on the preservation of fungal and bacterial residues in the coarse‐textured soils of the South African Highveld. Composite samples were taken from the top 20 cm of soils (Plinthustalfs) that have been cropped for periods varying from 0 to 98 years in each of three different agro‐ecosystems in the Free State Province. Amino sugars were determined as markers for the microbial residues in bulk soil and its particle‐size fractions. Long‐term cultivation reduced N in the soil by 55% and the contents of amino sugars by 60%. Loss rates of amino sugars followed bi‐exponential functions, suggesting that they comprised both labile and stable fractions. With increased duration of cropping the amino sugars attached to silt dissipated faster than those associated with the clay. This dissipation was in part because silt was preferentially lost through erosion, while clay particles (and their associated microbial residues) remained. Erosion was not solely responsible for the reduction in amino sugar concentrations, however. Bacterial amino sugars were lost in preference to fungal ones as a result of cultivation, and this effect was evident in both silt‐ and clay‐sized separates. This shift from fungal to bacterial residues was most pronounced within the first 20 years after converting the native grassland to arable cropland, but continued after 98 years of cultivation.

Effects of deforestation on contents and distribution of amino sugars within particle-size fractions of mountain soils

Identifying amino sugar pools in soil may advance our knowledge about microbially derived substances. Our objective was to study the effects of deforestation followed by pasture establishment on amino sugar contents and patterns in mountain soils of the Sui Checti Valley in the Alay Range, Kyrgyzia. Soil A horizons (0–10 cm) under pasture and forest were fractionated into clay, silt, fine and coarse sand fractions. Soil organic C, N, glucosamine (GlcN), galactosamine, mannosamine and muramic acid (MurAc) were analysed in the fine earth, particle-size fractions and humus layers. Deforestation of Juniperus turkestanica and pasture establishment led to a significant increase in the amino sugar content in the fine earth and soil organic matter (SOM) reflecting different accumulation of amino sugars in different ecosystems. Deforestation affected principally the amino sugars in the coarse and fine sand fractions that generally are related to particulate organic matter. High concentrations of amino sugars were found in the clay fraction, corroborating the general assumption that it contains a high microbial biomass and microbially altered organic matter. The pasture soil samples have a significantly higher GlcN to MurAc ratio indicating a higher fungal contribution to SOM than in forest soils. Although other studies revealed that pasture is associated with high amounts of bacterial amino sugars, our study gave evidence that deforestation tends to lead to the accumulation of mainly fungi-derived amino sugars. It is proposed that this might be due to a lowering of soil pH.

Leaf Exudates of Vicia faba and their Effects on Botrytis fabae and Some Associated Fungi

Analysis of leaf exudates of Vicia faba using paper chromatography to identify individual amino acids and sugars qualitatively was investigated. The results revealed that the number of identified amino acids detected in the leaf exudates of the susceptible plants was more than those of resistant plants. The results also showed an increase in the number of amino acids exuded by infected leaves, but no marked difference in sugars of infected and non infected plants. Lithium chloride application led to decrease in amino acid and sugar contents. The number of amino acids and sugars was also decreased with leaf age. Botrytis fabae and the selected fungal species (Alternaria alternata, Fusarium oxysporum and Aspergillus niger) were used to show the effect of individual amino acid and sugar on their spore germination. It was observed that all amino acids stimulated the fungal spore germination except serine which inhibited its spore germination. In case of A. alternata, spore germination was stimulated by all amino acids except serine, alanine, glutamic acid, arginine and methionine which caused the inhibition. In case of F. oxysporum, aspartic and glutamic acids inhibited spore germination but the other amino acids stimulated its spore germination. Aspartic acid and phenyl alanine inhibited the spore germination of A. niger. All the identified sugars (galactose, glucose, fructose and rhamnose) stimulated spore germination of all tested fungi.

Restoration of Microbial Residues in Soils of the Conservation Reserve Program

To elucidate the role of microorganisms for C and N sequestration in arable soils converted to grassland (sites of the Conservation Reserve Program; CRP), we determined amino sugars as indicators for microbial residues in surface samples (0–5 cm) obtained from each of 10 adjacent native grassland, CRP, and cropland sites across the U.S. Great Plains. The CRP sites were 6 to 10 yr and the cropland sites were >80 yr old. Compared with native grasslands, the CRP sites had lost between 17 and 50% and the cropland sites between 32 and 94% of their surface soil organic matter (SOM). The C/N ratio was not significantly different among the three land‐use systems, indicating that C and N losses occurred at similar intensity. The mean amino sugar concentrations decreased in the order native grassland (70 g kg−1 C; 750 g kg−1 N) > CRP (53 g kg−1 C; 570 g kg−1 N) > cropland (47 g kg−1 C; 450 g kg−1 N). This decrease in the element‐normalized concentrations of amino sugars indicated that they responded faster to management than other C or N containing compounds. The response of individual amino sugars related to soil compaction and the temperature regime. We suggest that the resequestration of C and N into the residues of bacteria and fungi requires several years, but as it depends on land use it could be manipulated using, for example, soil decompacting techniques to improve CRP efficiency.

FATE OF MICROBIAL RESIDUES DURING LITTER DECOMPOSITION AS AFFECTED BY MINERALS

Minerals may protect organic matter against microbial decay, either by direct chemical and physical interactions or by inhibitory effects on the soil microbial community. To clarify the effects of minerals on organic matter cycling by microorganisms, we used amino sugars as tracers for C and N in dead microbial cells after 0, 15, 29, 90, 239, and 498 days of incubation of beech leaf litter mixed with quartz sand, Fe oxide, Al hydroxide, or Mn oxide. Beech leaf litter without addition of any mineral phases was used as the control. The results show that amino sugar concentrations increased as litter decomposition proceeded. Decreasing ratios of glucosamine to muramic acid and of glucosamine to galactosamine indicated that bacterial products accumulated increasingly relative to fungal cells with increasing incubation time. As the presence of Mn oxide promoted losses of plant-derived C, there was a more pronounced selective accumulation of the microbial-derived amino sugar C than in the other treatments. Aluminium hydroxide and Fe oxide inhibited synthesis of bacterial amino sugars by a factor of two. This resulted in lower amino sugar C proportions compared with the other treatments. Consequently, the amino sugar C proportions were sensitive to both increasing amino sugar synthesis and C mineralization rates. In contrast, the amino sugar N proportions were not affected by any mineral additions. Thus, the mere presence of minerals did not affect the cycling of N through the amino sugar pool, but minerals altered the relative proportions of N sequestered within residues of bacteria and fungi.

Effects of NaCl-salinity on amino acid and carbohydrate contents of Phragmites australis

The effects of NaCl-salinity on growth, free amino acid and sugar content and composition were assayed in roots, rhizomes and leaves of Phragmites australis (Cav.) Trin. ex Steud. Juvenile plants produced from freshwater clones, were cultured under greenhouse hydroponic conditions for 21 days. Relative growth rates were highest at a salinity level of 0 and 1.5‰, respectively, but decreased significantly at 10‰. All plants cultured at 35‰ salinity died. The osmolality in rhizomes and leaves increased with salinity. The total contents of free amino acids were highest in rhizomes>leaves>roots. In rhizomes, the amino acid content increased significantly up to four-fold from 0 to 10‰ salinity. This increase was caused by up to 200-fold increase of proline and 11-fold increase of glutamine at 10‰, whilst the share of asparagine and glutamate decreased. Leaves showed a similar response to salinity with increasing amino acid contents, and shares of proline and glutamine whereas roots did not react significantly. The contents of sucrose, glucose and fructose were highest in leaves>rhizomes>roots. In rhizomes of all three clones, the sugar contents increased up to 3.5-fold from 1.5 to 10‰ salinity level, but were lower at 1.5‰ versus the control (0‰). Sugar contents were lowest (roots) and highest (leaves) at 1.5‰ salinity. The sugar composition did not vary significantly except for leaves where the fraction of sucrose decreased with increasing salinity level at all three clones from 89.1 to 61.7% of total dissolved sugar (pooled data). The importance of free amino acids and sugars as osmolytes was similar in rhizomes and leaves (13–15% of total osmolality at 10‰). In rhizomes, free amino acids were more important as osmolyte than sugars, while the opposite was true for leaves. Proline contributed up to 2.7% to total osmolality. It is hypothesised that a strong proline accumulation indicates the exceeding of a critical salinity level.

Land use effects on amino sugar signature of chromic Luvisol in the semi-arid part of northern Tanzania

Characterizing amino sugar signature in particle size separates of tropical soils is important for further understanding the fate of microbial-derived compounds during the decomposition of soil organic matter (SOM) in tropical agroecosystems. We investigated the impact of land-use changes on the nature, amount and dynamics of amino sugars in soil of the semi-arid northern Tanzania. Samples were collected from the uppermost 10 cm of native woodland, degraded woodland, fields cultivated for 3 and 15 years and homestead fields fertilized with animal manure. The amount of glucosamine, galactosamine, mannosamine and muramic acid were determined in bulk soil and size separates. Compared to the native woodland, a 68% and 72% reduction in total amino sugar contents were found in the 3- and 15-year cultivated fields, respectively. Moreover, 39% of the total amino sugar was lost from the degraded woodland. This may be attributed to accelerated decomposition of amino sugars and/or decreasing microbial biomass input under the semi-arid environment following clear-cutting and cultivation. In contrast, only a 20% decline was found from the fields where animal manure had been applied. Most of the amino sugar depletion occurred from the coarse and fine sand-associated SOM. The decline from the silt and clay-bound amino sugar was relatively small, indicating the importance of organo-mineral associations in the stabilization of microbial-derived sugars in this tropical soil. After 15 years of continuous cultivation, the ratio of glucosamine:galactosamine increased from 1.44 to 2.23, while the ratio of glucosamine:muramic acid increased from 14.5 to 26.5 (P<0.05). These results suggest that cultivation may have led to preferential depletion of bacterial-derived amino sugars (muramic acid and galactosamine) compared with fungal-derived glucosamine.

Delayed greening of mountain birch leaves:Ecological and chemical correlates

Flushing leaves of deciduous trees can be exposed to high herbivore pressure. Young foliage provides high quality food for herbivores, and therefore herbivore pressure is much higher in young than mature foliage. Plants may escape the effects of herbivory in time by delaying leaf greening. We measured delayed greening as an intensity of redness in leaves in mountain birch at bud burst. Furthermore, we analyzed covariation of leaf redness with leaf growth and leaf consumption by the autumnal moth, Epirrita autumnata (Bkh.), a major defoliator of mountain birch. We also analyzed concentrations of amino acids, sugars and phenolic compounds of leaves. Leaf redness was positively associated with leaf growth, and consumption by E. autumnata indicated reduced leaf resistance against herbivores. Concentrations of protein-bound amino acids and gallotannins in young leaves were closely and positively correlated with leaf redness. Concentrations of glucose exhibited close positive correlations with leaf redness at the beginning of the season, whereas the correlation was negligible in mature leaves. Concentrations of other sugars increased with increasing degree of leaf redness towards the end of leaf development. This may be one reason for high leaf biomass losses in trees with delayed greening.

Effect of modified atmosphere packaging (MAP) and controlled atmosphere (CA) storage on the quality of snow pea pods (Pisum sativum L. var. saccharatum)

The effects of precooling, modified atmosphere packaging (MAP) and controlled atmosphere (CA) storage on the storability of snow pea pods ( Pisum sativum L. var. saccharatum ) at 5°C were determined. Bagging pods with polymethyl pentene polymeric films (PMP) of 25 and 35 μm thickness, in conjunction with precooling, modified the in-bag atmosphere concentration to approximately 5 kPa O 2 and 5 kPa CO 2 , leading to better maintenance of the pod external quality (appearance and color), as well as internal quality (chlorophyll, ascorbic acid, and sugar contents). Sensory scores were also maintained. Under CA storage at 5°C, gas compositions ranging from 5 to 10 kPa O 2 with 5 kPa CO 2 were the best storage conditions of those tested, since changes in organic acid, free amino acid and sugar contents, and pod sensory attributes were slight, corroborating the MAP results. The appearance of pods stored under CA conditions was much better than that of air-stored pods (control). Low O 2 (2.5 kPa with 5 kPa CO 2 ) and high CO 2 (10 kPa with 5 kPa O 2 ) concentrations have a detrimental effect on quality of stored pods since they developed slight off-flavors, but this effect is reversible since it was partially alleviated after ventilation.

Structure and function of the soil microbial community in microhabitats of a heavy metal polluted soil

Particle-size fractionation of a heavy metal polluted soil was performed to study the influence of environmental pollution on microbial community structure, microbial biomass, microbial residues and enzyme activities in microhabitats of a Calcaric Phaeocem. In 1987, the soil was experimentally contaminated with four heavy metal loads: (1) uncontaminated controls; (2) light (300 ppm Zn, 100 ppm Cu, 50 ppm Ni, 50 ppm V and 3 ppm Cd); (3) medium; and (4) heavy pollution (two- and threefold the light load, respectively). After 10 years of exposure, the highest concentrations of microbial ninhydrin-reactive nitrogen were found in the clay (2–0.1 μm) and silt fractions (63–2 μm), and the lowest were found in the coarse sand fraction (2,000–250 μm). The phospholipid fatty acid analyses (PLFA) and denaturing gradient gel electrophoresis (DGGE) separation of 16S rRNA gene fragments revealed that the microbial biomass within the clay fraction was predominantly due to soil bacteria. In contrast, a high percentage of fungal-derived PLFA 18 : 2ω6 was found in the coarse sand fraction. Bacterial residues such as muramic acid accumulated in the finer fractions in relation to fungal residues. The fractions also differed with respect to substrate utilization: Urease was located mainly in the phosphatase >urease >xylanase. Heavy metal pollution did not markedly change the similarity pattern of the DGGE profiles and amino sugar concentrations. Therefore, microbial biomass and enzyme activities seem to be more sensitive than 16S rRNA gene fragments and microbial amino-sugar-N to heavy metal treatment.

Plant Residue and Bacteria as Bases for Increased Stool Weight Accompanying Consumption of Higher Dietary Fiber Diets

Objective: Stool diluting effects of relatively inert material, such as unfermentable dietary fiber, has been proposed as an effect of fiber beneficial to the colon. Stool dilution by increasing bacterial mass may be beneficial or deleterious, depending on bacterial metabolic products. The purpose of this study was to determine the basis for stool weight when two stepwise increases of fiber from all classes of fiber-containing foods were consumed.Methods: Stool from five men consuming three constant diets containing 15, 30 and 42 g/d of dietary fiber were fractionated into plant material and bacteria and analyzed for neutral and amino sugar content. Fecal nitrogen, fat and ash were measured.Results: Daily gravimetric yield and sugar content of the plant fraction from stool increased with each fiber addition. Compared to the low fiber diet, the medium fiber diet decreased the concentration of the bacterial mass in wet stool by 11% and the high fiber diet by an additional 32%. The high fiber diet decreased stool fat concentration; the medium and high fiber diets decreased stool nitrogen concentration to the same extent. Apparent digestibility of plant-derived neutral sugars decreased with each fiber addition.Conclusions: Inherently less fermentable plant material modulates the colon environment in three beneficial ways: it is a relatively unreactive diluent of lumenal contents; it adds mass to promote distal movement of waste; it does not promote a large bacterial mass.

Feeding the world in the 21st century

The effects of the ‘Green Revolution’ cannot keep pace with today’s pace of population growth. A combination of problems has led to a decline in agricultural production and although in theory sufficient food is produced worldwide, the operation of market economies means that the equal distribution of food is not a reality. The prognosis is not good with >800 million people living a life of permanent or intermittent hunger. The application of advances in plant breeding, particularly tissue culture and genetic engineering, will be essential if the yields of farmers and yield ceilings are to be increased. The use of excessive quantities of pesticide needs to be reduced and the nutrient value of basic foods increased. Farmers on less-favored lands need plant varieties that are better able to tolerate drought, salinity and lack of soil nutrients. The required input traits of plants are: resistance to parasites in various crops; delayed senescence, dwarfing, reduced shade avoidance and early flowering in rice; tolerance to aluminum, chilling and freezing in cereals; new plant types for weed control and for increased yield potential in rice. The required output traits of plants are: increased β-carotene in rice and oilseed rape; increased bioavailable iron in maize and rice; modified starch in rice, potato and maize; modified fatty-acid content in oilseed rape; increased bioavailable protein, essential amino acids, seed weight and sugar content in maize; lowered inert cellulose (lignin) content in forage crops. Nature (2000), 402 (Suppl.), C55–C58.

The role of low-level ozone exposure and mycorrhizas in chemical quality and insect herbivore performance on Scots pine seedlings

The effects of low-level ozone exposure and suppression of natural mycorrhizas on the above-ground chemical quality of Scots pine (Pinus sylvestris L.) needles and insect herbivore performance were studied in a two-year field experiment. Seedlings were fumigated with the ozone doses 1.5–1.7 times the ambient, and natural mycorrhizal infection level was about 35% reduced in roots with fungicide propiconazole. On ozone-exposed seedlings the mean relative growth rate (MRGR) of Lygus rugulipennis Popp. nymphs was lower than on ambient ozone seedlings, but Gilpinia pallida Klug sawfly larvae grew better on elevated ozone seedlings than on ambient ozone seedlings. MRGR of Schizolachnus pineti Fabr. and Cinara pinea L. aphid nymphs or Neodiprion sertifer Geoffr. sawfly larvae or the oviposition of L. rugulipennis and N. sertifer were not affected by ozone exposure. Although ozone exposure did not affect total phenolics, total terpene, total or individual resin acid, total free amino acid, nutrient or sugar concentrations in needles, MRGR of L. rugulipennis positively correlated with total terpenes and MRGR of G. pallida positively with total amino acids. In addition, ozone exposure increased serine and proline concentration and marginally also starch concentration in needles. When mycorrhizas were reduced with fungicide, only MRGR of L. rugulipennis nymphs increased, but performance of other insect herbivores studied was not changed. However, number of L. rugulipennis eggs correlated positively with mycorrhizal infection level and also with total sugars. Reduction of mycorrhizas did not strongly affect the concentrations of analysed compounds in needles, because only phosphorus and potassium and some individual resin acids were reduced by fungicide treatment. These results suggest that low-level ozone exposure and moderately declined mycorrhizal infection do not drastically affect either the above-ground chemical quality of Scots pine seedlings or performance of studied insect herbivores. (Less)

Calcium effect on the mycelial cell walls of Botrytis cinerea

The goal of this study was to determine whether calcium ion, (one of the electrolytes released after plant cell attack), may have a direct effect on fungal growth and chemistry of the fungal cell wall. B. cinerea was grown on Richard's solution containing different amounts of CaCl 2, and the cell walls were extracted from the mycelium after 7 days of growth. Mineral, neutral and aminosugar, protein and uronic acid contents were determined. At 1 g l −1 CaCl 2, only the aminosugar content increased. At 2 g l −1 CaCl 2, neutral sugar synthesis was reduced, whereas the uronic acid content increased. For higher CaCl 2 concentrations, the calcium ion content of the cell wall increased, resulting in reduced protein and neutral sugar contents. Meanwhile, the cell wall proportion of the mycelia increased on a dry weight basis due to an increase in uronic acid, Ca, P, Na and neutral sugar contents of the cell wall with increasing CaCl 2 in the media. The resulting thickening of the fungal cell wall caused by calcium ion may be an important factor in the host-pathogen relationship.

Bacterial and Fungal Cell‐Wall Residues in Conventional and No‐Tillage Agroecosystems

Agricultural management practices have been shown to influence the decomposer community in soils, with no‐tillage (NT) systems favoring fungi as compared with conventional tillage (CT) systems. In this study, we examined six North American agroecosystems with respect to the effects of NT vs. CT management systems on the accrual of microbial cell‐wall residues in surface soil. We used total amino sugar contents to estimate living and decomposing microbial cell‐wall mass in soil and the contents of glucosamine and muramic acid to separate fungal and bacterial contributions to microbial‐derived soil organic matter (SOM). Compared with estimates of glucosamine and muramic acid present in living biomass of fungi and bacteria, total concentrations of these compounds (745–2076 mg glucosamine kg−1 soil and 37–79 mg muramic acid kg−1 soil) were larger by factors of 54 to 745 and 26 to 82, respectively. At three sites, the ratios of glucosamine to muramic acid in NT soils (32.0, 30.0, 42.2) significantly exceeded those in the respective CT soils (18.8, 22.1, 23.0) because of a higher enrichment of glucosamine. This coincided with higher values for fungal biomass, particulate organic matter carbon (POM‐C), mean weight diameter of water‐stable aggregates (MWD), and total organic carbon (TOC). Analysis of aggregate‐size classes showed that the additional glucosamine accumulated in &gt;53‐mm aggregates but not in smaller particles. The enrichment of SOM in fungal‐derived glucosamine suggests that the accrual of hyphal cell‐wall residues is an important process in the three NT agroecosystems which leads to higher SOM storage in surface soil concurrent with an increase in aggregate stability. The other soils, having a lower clay plus silt content, exhibited no significant differences in POM‐C, MWD, and total amino sugars between NT and CT management systems. We suggest that at lower clay plus silt contents the beneficial potential for NT to sequester microbial‐derived SOM is lower because of limited physical stabilization.

Effect of drying time, bean depth and temperature on free amino acid, peptide-N, sugar and pyrazine concentrations of Malaysian cocoa beans

The effect of drying time on free amino acid, peptide-N, sugar and pyrazine concentrations as well as the influence of bean depth and temperature on these compounds during cocoa drying was studied. Drying time, bean depth and temperature significantly decreased the concentration of free amino acids, peptide-N, total reducing sugars and sucrose and increased the concentration of trimethyl-, tetramethylpyrazine and total pyrazines in cocoa beans. The best drying treatment was obtained at the combination of bean depth/drying temperature of 8.3 cm/40 °C. This was based on the fact that it produced significantly high concentrations of hydrophobic free amino acids, peptide-N and total reducing sugars and significantly low concentration of trimethyl-, tetramethylpyrazine and total pyrazines. Drying treatment of 1.5 cm/60 °C significantly produced the lowest concentration of free amino acids, peptide-N and total reducing sugars and the highest concentration of pyrazines. © 1999 Society of Chemical Industry

Effect of drying time, bean depth and temperature on free amino acid, peptide‐N, sugar and pyrazine concentrations of Malaysian cocoa beans

The effect of drying time on free amino acid, peptide-N, sugar and pyrazine concentrations as well as the influence of bean depth and temperature on these compounds during cocoa drying was studied. Drying time, bean depth and temperature significantly decreased the concentration of free amino acids, peptide-N, total reducing sugars and sucrose and increased the concentration of trimethyl-, tetramethylpyrazine and total pyrazines in cocoa beans. The best drying treatment was obtained at the combination of bean depth/drying temperature of 8.3 cm/40 °C. This was based on the fact that it produced significantly high concentrations of hydrophobic free amino acids, peptide-N and total reducing sugars and significantly low concentration of trimethyl-, tetramethylpyrazine and total pyrazines. Drying treatment of 1.5 cm/60 °C significantly produced the lowest concentration of free amino acids, peptide-N and total reducing sugars and the highest concentration of pyrazines. © 1999 Society of Chemical Industry

Land-use effects on amino sugars in particle size fractions of an Argiudoll

Identifying amino sugar pools from different land-use systems may advance our knowledge of land-use effects on the fate of microbially-derived substances. Surface soils (0–10 cm) from (1) native pasture, (2) a >80-years-arable site, and (3) a >80-years-afforested site were fractionated into clay, silt, fine-, and coarse-sand fractions. Then, soil organic carbon, N, glucosamine, galactosamine, mannosamine, and muramic acid were analyzed. Afforestation did not influence the amino sugar content in bulk soil, whereas cultivation reduced the content by 54%. The concentrations of amino sugars in g kg −1 SOM declined after both long-term cropping and afforestation by 6% and 13%, respectively, relative to that in the grassland. The amino sugar depletion at the forest site occurred mainly from the silt fraction (by 25%), while that in the cultivated site was mainly due to preferential loss of amino sugars from clay (by 19% compared with the grassland). Both ratios of glucosamine to galactosamine and glucosamine to muramic acid increased when the prairie was converted to forest or cultivated land, suggesting that bacterial N especially is better preserved than fungal N under prairie conditions.

Amino Sugars in Native Grassland Soils along a Climosequence in North America

AbstractCharacterizing amino sugars is important for further understanding soil organic matter (SOM) dynamics in terrestrial ecosystems. This study was designed to evaluate the impact of climate on amino sugars in 18 surface soil (0–10 cm) samples along a climosequence of native grasslands from central Saskatchewan, Canada, to Southern Texas, USA. Mean annual temperature (MAT) ranged from 0.9 to 23.4°C and mean annual precipitation (MAP) from 300 to 1308 mm. In all samples, the contents of soil organic C, glucosamine, mannosamine, galactosamine, and muramic acid were determined. Both the ratios of glucosamine to galactosamine and of glucosamine to muramic acid were related to the moisture regime. With increasing MAP, increasing proportions of amino sugars were glucosamine. This glucosamine is possibly derived from the chitin of fungi. The proportion of bacterial‐derived amino sugars, such as muramic acid, declined as MAP increased. The relationship between amino sugar concentrations (mg kg‐1 soil organic C) and MAT followed a parabolic regression model; the maximum of the amino sugar concentration occurring at the mesic temperature regime. On the basis of hierarchical cluster analysis the sites could be divided into two groups, which coincided with the Northern‐central and Southern grasslands. We hypothesize that in the Northern‐central grasslands frost limits amino sugar production whereas in the Southern grasslands higher winter temperatures &gt;0°C favor amino sugar decomposition.