Zhongqi He - Academia.edu (original) (raw)
Papers by Zhongqi He
Hedley et al (1982) sequential fractionation has been widely used for investigating the forms and... more Hedley et al (1982) sequential fractionation has been widely used for investigating the forms and transformations of soil P under various environmental conditions. Where this approach considers both inorganic and organic P (difference between total P and inorganic P) to exist in water, NaHCO3 and NaOH fractions, inorganic P is assumed to only exist in the HCl fraction. In this
Biodegradation of Nitroaromatic Compounds and Explosives, 2000
Applied and environmental microbiology, 1998
Pseudomonas pseudoalcaligenes JS45 utilizes nitrobenzene as the sole source of nitrogen, carbon, ... more Pseudomonas pseudoalcaligenes JS45 utilizes nitrobenzene as the sole source of nitrogen, carbon, and energy. Previous studies have shown that degradation of nitrobenzene involves the reduction of nitrobenzene to nitrosobenzene and hydroxylaminobenzene, followed by rearrangement to 2-aminophenol, which then undergoes meta ring cleavage to 2-aminomuconic semialdehyde. In the present paper, we report the enzymatic reactions responsible for the release of ammonia after ring cleavage. 2-Aminomuconic semialdehyde was oxidized to 2aminomuconate in the presence of NAD by enzymes in crude extracts. 2-Aminomuconate was subsequently deaminated stoichiometrically to 4-oxalocrotonic acid. No cofactors are required for the deamination. Two enzymes, 2-aminomuconic semialdehyde dehydrogenase and a novel 2-aminomuconate deaminase, distinguished by partial purification of the crude extracts, catalyzed the two reactions. 4-Oxalocrotonic acid was further degraded to pyruvate and acetaldehyde. The key enzyme, 2-aminomuconate deaminase, catalyzed the hydrolytic deamination that released ammonia, which served as the nitrogen source for growth of the organism.
Journal of bacteriology, 1998
2-Aminonumconic 6-semialdehyde is an unstable intermediate in the biodegradation of nitrobenzene ... more 2-Aminonumconic 6-semialdehyde is an unstable intermediate in the biodegradation of nitrobenzene and 2-aminophenol by Pseudomonas pseudoalcaligenes JS45. Previous work has shown that enzymes in cell extracts convert 2-aminophenol to 2-aminomuconate in the presence of NAD+. In the present work, 2-aminomuconic semialdehyde dehydrogenase was purified and characterized. The purified enzyme migrates as a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with a molecular mass of 57 kDa. The molecular mass of the native enzyme was estimated to be 160 kDa by gel filtration chromatography. The optimal pH for the enzyme activity was 7.3. The enzyme is able to oxidize several aldehyde analogs, including 2-hydroxymuconic semialdehyde, hexaldehyde, and benzaldehyde. The gene encoding 2-aminomuconic semialdehyde dehydrogenase was identified by matching the deduced N-terminal amino acid sequence of the gene with the first 21 amino acids of the purified protein. Multiple sequ...
Journal of bacteriology, 1998
2-Aminomuconate, an intermediate in the metabolism of tryptophan in mammals, is also an intermedi... more 2-Aminomuconate, an intermediate in the metabolism of tryptophan in mammals, is also an intermediate in the biodegradation of nitrobenzene by Pseudomonas pseudoalcaligenes JS45. Strain JS45 hydrolyzes 2-aminomuconate to 4-oxalocrotonic acid, with the release of ammonia, which serves as the nitrogen source for growth of the microorganism. As an initial step in studying the novel deamination mechanism, we report here the purification and some properties of 2-aminomuconate deaminase. The purified enzyme migrates as a single band with a molecular mass of 16.6 kDa in 15% polyacrylamide gel electrophoresis under denaturing conditions. The estimated molecular mass of the native enzyme was 100 kDa by gel filtration and 4 to 20% gradient nondenaturing polyacrylamide gel electrophoresis, suggesting that the enzyme consists of six identical subunits. The enzyme was stable at room temperature and exhibited optimal activity at pH 6.6. The Km for 2-aminomuconate was approximately 67 microM, and t...
Soil phosphatase and urease activities which are responsible for P and N mineralization, respecti... more Soil phosphatase and urease activities which are responsible for P and N mineralization, respectively, could be indicators of soil health for nutrient availability. In this work, we measured the activities of acid phosphatase, alkaline phosphatase, phosphodiesterase, and non-buffered and buffered urease in soils under rainfed and irrigated potato with different crop rotation managements. Compared with continuous potato (Solanum tuberosum L.) production, three-year rotation practices increased all soil enzyme activities in rainfed condition by 10 to 86%. Irrigation increased alkaline phosphatase, phosphodiesterase, and both unbuffered and buffered urease activities, but decreased acid phosphatase activity compared with no irrigation. Under rainfed management, microbial biomass C level was highly correlated with phosphatase and urease activities. When measured under buffered conditions, urease activity was highly correlated with rainfed potato yield. To the extent that urease is an indicator of plant N availability, this may reflect the influence of N availability on yield. This study showed that both cropping system and water management influence the activities of several enzymes considered important for plant uptake of N and P.
Accurate prediction of nitrogen (N) availability from manure is required for efficient utilizatio... more Accurate prediction of nitrogen (N) availability from manure is required for efficient utilization of this resource in crop production. This study was conducted to evaluate the impacts of temperature, water regime and selected soils on N availability from a liquid dairy (Bos taurus) manure. Two Maine soils [Caribou sandy loam (fine-loamy, mixed, frigid Typic Haplorthod) and ‘Newport’ loam (unnamed variant of a Bangor silt loam; coarse-loamy, mixed, frigid Typic Haplorthod)] and an Illinois soil [Catlin silt loam (fine-silty, mixed, superactive, mesic Oxyaquic Arguidoll)] were incubated in the laboratory at 11, 18 and 25°C under constant (60% water filled pore space, WFPS) and fluctuating (60 to 30% WFPS) water regimes, with and without dairy manure in a factorial arrangement. Ammonium concentrations increased immediately upon manure addition and declined thereafter as nitrate levels increased. Elevated NO3 levels reflected nitrification of NH4 added in the manure, with little additional net mineralization of manure organic N. Temperature strongly influenced NO3 concentration over time, but this effect could be described with the thermal unit (degree day) concept. The fluctuating water regime had no significant impact on manure-derived NO3 Changes in manure NO3 over thermal time could be described with a single exponential equation. However, less manure NO3 was observed in an Illinois soil than in two Maine soils. Separate particle size analysis and microbial community assessments indicate higher N immobilization potential in the Illinois soil. Because soil type strongly impacted N availability, it is clear that additional soils with ranges in several physical, chemical and biological properties should be investigated to quantify these relationships with manure N availability.
ABSTRACT Solid state 13C nuclear magnetic resonance (NMR) spectroscopy is a common tool to study ... more ABSTRACT Solid state 13C nuclear magnetic resonance (NMR) spectroscopy is a common tool to study the structure of soil humic fractions; however, knowledge regarding carbon structural relationships in humic fractions is limited. In this study, mobile humic acid (MHA) and recalcitrant calcium humate (CaHA) fractions were extracted from eight soils collected from six US states and representing a variety of soils and ecoregions, characterized by this spectroscopic technique and analyzed for statistical significance at P = 0.05. We found that the abundances of COO and N-C=O functional groups in the MHA fractions were negatively correlated to soil sand content, but were positively correlated to silt, total N and soil organic carbon contents. In contrast, the abundances of the COO and N-C=O functional groups were only positively correlated to the content of clay in the CaHA fractions, indicating that the two humic fractions were associated with different soil components. The two 13C NMR peaks representing alkyls and OCH3/NCH were negatively correlated to the peaks representing aromatics, aromatic C-O and N-C=O/COO. Comparison of the sets of data from 13C NMR spectroscopy and ultrahigh resolution mass spectrometry revealed that the aromatic components identified by the two methods were highly consistent. The comparison further revealed that protein in MHA was associated with, or bound to, the nonpolar alkyl groups, but a component competitively against (or complementary to) aromatic groups in the MHA composition. These observations provided insight on the internal correlations of the functional groups of soil humic fractions.
Hedley et al (1982) sequential fractionation has been widely used for investigating the forms and... more Hedley et al (1982) sequential fractionation has been widely used for investigating the forms and transformations of soil P under various environmental conditions. Where this approach considers both inorganic and organic P (difference between total P and inorganic P) to exist in water, NaHCO3 and NaOH fractions, inorganic P is assumed to only exist in the HCl fraction. In this
Biodegradation of Nitroaromatic Compounds and Explosives, 2000
Applied and environmental microbiology, 1998
Pseudomonas pseudoalcaligenes JS45 utilizes nitrobenzene as the sole source of nitrogen, carbon, ... more Pseudomonas pseudoalcaligenes JS45 utilizes nitrobenzene as the sole source of nitrogen, carbon, and energy. Previous studies have shown that degradation of nitrobenzene involves the reduction of nitrobenzene to nitrosobenzene and hydroxylaminobenzene, followed by rearrangement to 2-aminophenol, which then undergoes meta ring cleavage to 2-aminomuconic semialdehyde. In the present paper, we report the enzymatic reactions responsible for the release of ammonia after ring cleavage. 2-Aminomuconic semialdehyde was oxidized to 2aminomuconate in the presence of NAD by enzymes in crude extracts. 2-Aminomuconate was subsequently deaminated stoichiometrically to 4-oxalocrotonic acid. No cofactors are required for the deamination. Two enzymes, 2-aminomuconic semialdehyde dehydrogenase and a novel 2-aminomuconate deaminase, distinguished by partial purification of the crude extracts, catalyzed the two reactions. 4-Oxalocrotonic acid was further degraded to pyruvate and acetaldehyde. The key enzyme, 2-aminomuconate deaminase, catalyzed the hydrolytic deamination that released ammonia, which served as the nitrogen source for growth of the organism.
Journal of bacteriology, 1998
2-Aminonumconic 6-semialdehyde is an unstable intermediate in the biodegradation of nitrobenzene ... more 2-Aminonumconic 6-semialdehyde is an unstable intermediate in the biodegradation of nitrobenzene and 2-aminophenol by Pseudomonas pseudoalcaligenes JS45. Previous work has shown that enzymes in cell extracts convert 2-aminophenol to 2-aminomuconate in the presence of NAD+. In the present work, 2-aminomuconic semialdehyde dehydrogenase was purified and characterized. The purified enzyme migrates as a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with a molecular mass of 57 kDa. The molecular mass of the native enzyme was estimated to be 160 kDa by gel filtration chromatography. The optimal pH for the enzyme activity was 7.3. The enzyme is able to oxidize several aldehyde analogs, including 2-hydroxymuconic semialdehyde, hexaldehyde, and benzaldehyde. The gene encoding 2-aminomuconic semialdehyde dehydrogenase was identified by matching the deduced N-terminal amino acid sequence of the gene with the first 21 amino acids of the purified protein. Multiple sequ...
Journal of bacteriology, 1998
2-Aminomuconate, an intermediate in the metabolism of tryptophan in mammals, is also an intermedi... more 2-Aminomuconate, an intermediate in the metabolism of tryptophan in mammals, is also an intermediate in the biodegradation of nitrobenzene by Pseudomonas pseudoalcaligenes JS45. Strain JS45 hydrolyzes 2-aminomuconate to 4-oxalocrotonic acid, with the release of ammonia, which serves as the nitrogen source for growth of the microorganism. As an initial step in studying the novel deamination mechanism, we report here the purification and some properties of 2-aminomuconate deaminase. The purified enzyme migrates as a single band with a molecular mass of 16.6 kDa in 15% polyacrylamide gel electrophoresis under denaturing conditions. The estimated molecular mass of the native enzyme was 100 kDa by gel filtration and 4 to 20% gradient nondenaturing polyacrylamide gel electrophoresis, suggesting that the enzyme consists of six identical subunits. The enzyme was stable at room temperature and exhibited optimal activity at pH 6.6. The Km for 2-aminomuconate was approximately 67 microM, and t...
Soil phosphatase and urease activities which are responsible for P and N mineralization, respecti... more Soil phosphatase and urease activities which are responsible for P and N mineralization, respectively, could be indicators of soil health for nutrient availability. In this work, we measured the activities of acid phosphatase, alkaline phosphatase, phosphodiesterase, and non-buffered and buffered urease in soils under rainfed and irrigated potato with different crop rotation managements. Compared with continuous potato (Solanum tuberosum L.) production, three-year rotation practices increased all soil enzyme activities in rainfed condition by 10 to 86%. Irrigation increased alkaline phosphatase, phosphodiesterase, and both unbuffered and buffered urease activities, but decreased acid phosphatase activity compared with no irrigation. Under rainfed management, microbial biomass C level was highly correlated with phosphatase and urease activities. When measured under buffered conditions, urease activity was highly correlated with rainfed potato yield. To the extent that urease is an indicator of plant N availability, this may reflect the influence of N availability on yield. This study showed that both cropping system and water management influence the activities of several enzymes considered important for plant uptake of N and P.
Accurate prediction of nitrogen (N) availability from manure is required for efficient utilizatio... more Accurate prediction of nitrogen (N) availability from manure is required for efficient utilization of this resource in crop production. This study was conducted to evaluate the impacts of temperature, water regime and selected soils on N availability from a liquid dairy (Bos taurus) manure. Two Maine soils [Caribou sandy loam (fine-loamy, mixed, frigid Typic Haplorthod) and ‘Newport’ loam (unnamed variant of a Bangor silt loam; coarse-loamy, mixed, frigid Typic Haplorthod)] and an Illinois soil [Catlin silt loam (fine-silty, mixed, superactive, mesic Oxyaquic Arguidoll)] were incubated in the laboratory at 11, 18 and 25°C under constant (60% water filled pore space, WFPS) and fluctuating (60 to 30% WFPS) water regimes, with and without dairy manure in a factorial arrangement. Ammonium concentrations increased immediately upon manure addition and declined thereafter as nitrate levels increased. Elevated NO3 levels reflected nitrification of NH4 added in the manure, with little additional net mineralization of manure organic N. Temperature strongly influenced NO3 concentration over time, but this effect could be described with the thermal unit (degree day) concept. The fluctuating water regime had no significant impact on manure-derived NO3 Changes in manure NO3 over thermal time could be described with a single exponential equation. However, less manure NO3 was observed in an Illinois soil than in two Maine soils. Separate particle size analysis and microbial community assessments indicate higher N immobilization potential in the Illinois soil. Because soil type strongly impacted N availability, it is clear that additional soils with ranges in several physical, chemical and biological properties should be investigated to quantify these relationships with manure N availability.
ABSTRACT Solid state 13C nuclear magnetic resonance (NMR) spectroscopy is a common tool to study ... more ABSTRACT Solid state 13C nuclear magnetic resonance (NMR) spectroscopy is a common tool to study the structure of soil humic fractions; however, knowledge regarding carbon structural relationships in humic fractions is limited. In this study, mobile humic acid (MHA) and recalcitrant calcium humate (CaHA) fractions were extracted from eight soils collected from six US states and representing a variety of soils and ecoregions, characterized by this spectroscopic technique and analyzed for statistical significance at P = 0.05. We found that the abundances of COO and N-C=O functional groups in the MHA fractions were negatively correlated to soil sand content, but were positively correlated to silt, total N and soil organic carbon contents. In contrast, the abundances of the COO and N-C=O functional groups were only positively correlated to the content of clay in the CaHA fractions, indicating that the two humic fractions were associated with different soil components. The two 13C NMR peaks representing alkyls and OCH3/NCH were negatively correlated to the peaks representing aromatics, aromatic C-O and N-C=O/COO. Comparison of the sets of data from 13C NMR spectroscopy and ultrahigh resolution mass spectrometry revealed that the aromatic components identified by the two methods were highly consistent. The comparison further revealed that protein in MHA was associated with, or bound to, the nonpolar alkyl groups, but a component competitively against (or complementary to) aromatic groups in the MHA composition. These observations provided insight on the internal correlations of the functional groups of soil humic fractions.