Decomposition of glucose continuously added to soil

The continuous flow method was used to study the decomposition of uniformly tagged glucose in soil with different inorganic nitrogen and phosphorus levels. It was found that the amount of glucose carbon mineralized to carbon dioxide was higher if nitrogen and phosphorus were added together with the glucose. Some of the labelled carbon escaped from the soil and the amount of leached-out carbon was in inverse proportion to the amount of nitrogen and phosphorus in the soil. The level of mineral nutrient elements stimulated the rate of glucose mineralization in the initial phase of the continuous process. The rate of glucose mineralization in the steady state was stimulated in soil continuously enriched with glucose together with nitrogen and phosphorus. The quantitative relationship between the assimilation and oxidation of glucose carbon depended on the nitrogen and phosphorus concentration and was in inverse proportion to the mineral element level. The continuous addition of glucose stimulated decomposition of the native soil organic matter. The resultant priming effect was balanced, however, by the retention of glucose carbon in the soil, with the result that the carbon balance remained positive. The rate of glucose oxidation, the amount of carbon retained in the soil and the priming effect of glucose were strongly influenced by the flow rate.     

Microbial decomposition of carboxymethyl cellulose continuously added to the soil

If heterocontinuous flow-cultivation method was used to study the degradation of soluble carboxymethyl cellulose (CMC) in soil, neither the potential CM-cellulase activity of the soil nor the total degree of CMC mineralization significantly differed under aerobic condition and in a nitrogen atmosphere. In contrast, the end products of the enzymatic hydrolysis and their mutual proportions were different: under anaerobic conditions, the formation of reducing sugars was increased at the expense of CO₂ production and organic acids were detectable in the extract. The composition of soil microflora also differed. Addition of ammonium ions affected the maximum CM-cellulase activity in the soil, the degree of substrate mineralization, the proportion of CO₂ and reducing sugars that are formed and the concentration of the present soil microflora.     

Microflora participating in the decomposition of carboxymethyl cellulose continuously added to the soil

The microbial community in the soil was analyzed during four weeks of a continuous enrichment of structural chernozem soil samples with a 0.1% solution of carboxymethyl cellulose (CMC) under aerobic and semianaerobic conditions. During the first 14 d, the total amount of the aerobic and anaerobic, cellulose-degrading microorganisms increased significantly. Various metabolic pathways were u‘ed te decompose the substrate: diverse metabolic systems were activated and different groups of microorganisms preferred in dependence on the presence of oxygen or the source of mineral nitrogen. In the later phases of cultivation, a decrease in the concentration of zymogenous microflora and in the level of substrate mineralization was observed ovon though CM-cellulase activity remained high. During the fourth week of cultivation, a conspicuous increase in the numbers of oligothropic bacteria occurring in the colcnies of the microorganisms degrading cellulose was found. The representatives of prosthecobacteria (Caulobacter, Hyphomicrobium, Prosthecomicrobium spp.) andSeliberia sp. were thus identified. This “microflora of dispersion” attends the zymogenous microbes degrading CMC and indicates later phases of the process of decomposition.     

Effect of glucose on the decomposition of organic materials added to soil

The effect of glucose on the decomposition of plant material in soil was studied. Soil samples were enriched with different fractions of labelled alfalfa: the soluble dialyzable fraction, the soluble nondialyzable fraction, cellulose-lignin, lucerne meal. The added substances were decomposed for 42 days. One soil sample in every experimental variant was then percolated with water and another with 200 ml. 0.5% glucose for another 21 days. It was found that the effect of glucose on decomposition of the plant material depended on the latter’s composition and degree of decomposition. It was small in soils pre-enriched with soluble alfalfa fractions, decomposition of which was largely completed within the given time. Glucose markedly inhibited the release of radioactive carbon from the celluloselignin fraction and stimulated the formation of radioactive carbon dioxide from alfalfa meal.     

Effect of glucose and ribose on microbial degradation of the herbicide bromoxynil continuously added to soil

Bromoxynil (3,5-dibromo-4-hydroxybenzonitrile) was continuously added to chernozem (Haplic typic) soil inoculated with a suspension ofPseudomonas putida capable of cometabolic decomposition of the compound in a heterocontinuous-flow cultivation setup. In the steady state, when glucose or ribose were simultaneously added, 90 and 47% of the added herbicide was degraded per day, respectively. If the saccharides were absent, only 10–27% of the herbicide was decomposed. Addition and removal of glucose feeding resulted in an increase and decrease, respectively, of the degradation intensity, irrespective of the amount of the bacterial decomposers present. Two degradation products, 3,5-dibromo-4-hydroxy-benzamide and 3,5-dibromo-4-hydroxybenzoic acid, were formed during cultivation. The total amount of bromine-containing compounds was reduced only in the presence of glucose. Translated by Č. Novotny     

Effect of glucose on decomposition of vanillin by soil microorganisms

Oxygen consumption for the oxidation of vanillin in a soil suspension and in structural chernozem samples was accelerated in glucose-treated variants. The effect was observed on adding glucose and vanillin simultaneously and after 16 hours' preincubation of the soil with glucose. Glucose degradation was accompanied by an increase in the proportion of bacteria capable of utilizing vanillin as the sole carbon source, as well as by a general increase in the number of microorganisms. With some of these bacterial strains, in a given pH range, glucose induced the ability to oxidize vanillic acid, or at least shortened the lag phase of oxygen consumption for oxidation of this intermediate product of vanillin decomposition. Glutamic, malic, succinic and pyruvic acid and glycine, ribose and fructose were found to have a similar effect to glucose on the oxidation of vanillin in washed bacterial cell suspensions and on the incidence of vanillin decomposers in soil.     

Effect of a non-ionic surfactant added to the soil surface on the biodegradation of aromatic hydrocarbons within the soil

A study was conducted to determine whether a non-ionic surfactant (Novel II 1412-56) added to the surface of Lima silt loam would enhance the biodegradation of phenanthrene and biphenyl present within the soil. Water containing the surfactant at concentrations of 10 and 100 g/ml was pumped through the soil. At 10 g/ml, Novel II 1412-56 markedly enhanced the rate and extent of phenathrene mineralization and the extent but not the initial rate of biphenyl mineralization. The stimulation was less if the water added to the soil surface contained 100 g surfactant/ml. Addition of the surfactant at the two concentrations did not result in leaching of either phenanthrene or biphenyl, but products of the degradation were found in the soil leachate with or without the surfactant. We suggest that surfactants at low concentrations may be useful for in-situ bioremediation of sites contaminated with hydrophobic pollutants without causing movement of the parent compounds to ground-waters.     

杉木连栽土壤微生物多样性的比较研究

分析了位于湖南会同广坪镇1～4代人工杉木林根际土壤微生物数量变化情况,结果表明,随杉木连栽代数的增加,根际土壤中三大类群微生物数量发生显著变化,细菌和放线菌数量明显减少,真菌数量显著增加.利用PCR和DGGE技术分析了1～4代杉木林根际土壤细菌区系和真菌区系.结果表明,细菌生物多样性在不同连栽代数杉木根际土壤中变化不明显,各代杉木土壤之间细菌的遗传相似性为87%.而真菌随连栽代数的增加,DGGE图谱带逐渐减少,真菌生物多样性降低,各代杉木土壤之间真菌的遗传相似性也较低,仅为45%.对各代杉木土壤主要真菌类群的分析表明,随连栽代数的增加,病原真菌及产毒真菌增加显著.     

土壤施硒对烤烟生理指标的影响

以烤烟品种K326盆栽试验为基础,研究了不同浓度Se对烤烟生长过程中生理特性、烤烟叶片硒含量及硒积累速率的影响.结果表明:低浓度Se(≤8 mg/kg)对烤烟叶片中叶绿素a、叶绿素b、叶绿素a+b和类胡萝卜素含量有促进作用,可提高烤烟叶片中SOD、POD活性;高浓度硒(≥12mg/kg)降低了烤烟叶片SOD、POD活性,烟株生长受到抑制甚至死亡.在适宜的硒浓度范围内,烤烟MDA含量有所降低,缓解了膜脂的过氧化程度;POD活性随着生育期的延长而提高;烤烟生长前期的SOD活性高于后期;烤烟生长中期的MDA含量明显低于前期和后期.随着土壤中硒含量的增加,烤烟叶片中的硒含量逐渐递增,而硒在烤烟叶片中的积累速率呈现出先增高后降低的趋势.     

Anaerobic glucose and serine metabolism in Staphylococcus epidermidis

Anaerobically grown Staphylococcus epidermidis fermented glucose with the production of lactate and trace amounts of acetate, formate and CO2. Isotopic and inhibitor studies, assays for key enzymes of different metabolic pathways, and fermentation balances, all indicated that glucose was metabolized principally via glycolysis and to a very limited extent by the hexose monophosphate oxidative pathway. Serine fermentation proceeded via deamination and dismutation yielding NH3 and equimolar amounts of lactate, acetate and CO2; small amounts of formate arose by the operation of pyruvate-formate lyase. Incorporation of 0.5% (w/v) glucose in the growth medium depressed serine metabolism by repressing the activities of serine dehydratase and pyruvate dehydrogenase but, conversely, enhanced the activities of phosphofructokinase and lactate dehydrogenase. Glucose-grown organisms at various stages of anaerobic batch growth showed an inverse relationship between the rates of fermentation of serine and glucose. L-Lactate dehydrogenase activity in crude extracts depended on fructose 1,6-bisphosphate, and fructose 1,6-bisphosphate aldolase was found to be a class I aldolase. Despite the presence of ribokinase, D-ribose-5-phosphate isomerase, transaldolase and transketolase, the organisms utilized ribose only after growth aerobically in basal medium, and then at a slow rate after an initial lag period.     

The effects of cropping corn on the extractability of zinc added to a calcareous soil

The effects of cropping corn on the decrease in the extractability of Zn added to a calcareous soil were studied by a pot experiment and chemical extractions. The results show that the concentrations of Zn exchangeable with MgCl₂ (EXC-Zn) and extractable with DTPA (DTPA-Zn) in the soils with added Zn decreased with time. The processes associated with the decrease in extractability in DTPA of Zn added to soil can be described aptly by a diffusion equation which gives the proportion of added Zn in the non-DTPA fraction as a function of the square root of incubation time. This result suggests that the diffusion of Zn cations into microporous solids is a rate-limiting reaction. The relative diffusion rate coefficients (D/r²) were found to be 1.95×10^-10 and 3.34×10^-10 sec^-1 in the soils with added Zn of 20 and 60 mg kg^-1, respectively. Compared with uncropped soil, the concentrations of DTPA-Zn in the soils with added Zn were decreased by cropping. The decrease of DTPA-Zn in the soils in the presence of corn can be attributed to both its acquisition by corn and other processes associated with the growing of corn. The activity of plant roots would appear to enhance the process of decrease in the extractability in DTPA of Zn added to the soil. The source of Zn uptake by corn was affected by the loading or activity of Zn in soil. In the soil with low available Zn, the DTPA non-extractable Zn (non-DTPA-Zn) was mobilized and taken up by corn. In the soils with high available Zn, e.g. the recently added Zn, only EXC-Zn and a part of the DTPA-Zn were taken up by corn.     

Long-term continuously monocropped peanut significantly disturbed the balance of soil fungal communities

Journal of Microbiology - Balancing soil microbial diversity and abundance is critical to sustaining soil health, and understanding the dynamics of soil microbes in a monocropping system can help...     

Styrene formation by the decomposition by Pichia carsonii of trans-cinnamic acid added to a ground fish product.

It is not well known how the formation of styrene by microorganisms can occur in foods. In this study, we described and characterized the production of styrene by a yeast isolated from chikuwa fish paste. The styrene was not detected in fresh and normal food products nor in the food package's plastic film. The food containing styrene contained cinnamic acid as an antimicrobial agent and spice, and it was contaminated by 5.4 x 10(6) CFU of a yeast per gram. On the basis of morphological and biochemical features, the yeast isolated was determined to be a strain of Pichia carsonii, now designated strain CHI. Strain CHI, which was able to grow on cinnamic acid, had the ability to form styrene from trans-cinnamic acid via trans-p-coumaric and caffeic acids. The MIC of trans-cinnamic acid against strain CHI was 230 micrograms/ml. Strain CHI thrived well at pH 5.0 and 26.0 degrees C and was tolerant to 20% NaCl. Styrene was subsequently produced in ground fish meat containing cinnamic acid into which strain CHI had been inoculated. The yeast was found to be an environmental contaminant in food processing plants of the chikuwa manufacturer.     

Styrene formation by the decomposition by Pichia carsonii of trans-cinnamic acid added to a ground fish product.

It is not well known how the formation of styrene by microorganisms can occur in foods. In this study, we described and characterized the production of styrene by a yeast isolated from chikuwa fish paste. The styrene was not detected in fresh and normal food products nor in the food package's plastic film. The food containing styrene contained cinnamic acid as an antimicrobial agent and spice, and it was contaminated by 5.4 x 10(6) CFU of a yeast per gram. On the basis of morphological and biochemical features, the yeast isolated was determined to be a strain of Pichia carsonii, now designated strain CHI. Strain CHI, which was able to grow on cinnamic acid, had the ability to form styrene from trans-cinnamic acid via trans-p-coumaric and caffeic acids. The MIC of trans-cinnamic acid against strain CHI was 230 micrograms/ml. Strain CHI thrived well at pH 5.0 and 26.0 degrees C and was tolerant to 20% NaCl. Styrene was subsequently produced in ground fish meat containing cinnamic acid into which strain CHI had been inoculated. The yeast was found to be an environmental contaminant in food processing plants of the chikuwa manufacturer.