An ammonia-oxidizing strain of Penicillium sp., M25-22 which was isolated from chicken feces compost, was studied to make clear its characteristics of ammonium oxidation and provide references for its application in a...An ammonia-oxidizing strain of Penicillium sp., M25-22 which was isolated from chicken feces compost, was studied to make clear its characteristics of ammonium oxidation and provide references for its application in aerobic composting. In media containing （NH4）2SO4 at a concentration of 0.5 g 100 mL^-1, mycelium weight and utilization ratio of ammonium nitrogen increased markedly during the 1st 5 d, concentration of nitrate increased markedly from the 3rd to the 5th d and concentration of nitrite remained at a low level. The strain showed the ability to oxidize ammonium nitrogen growing in media containing glucose, sucrose, starch, or cellulose as the sole carbon source and to oxidize the negative trivalent nitrogen of ammonium sulfate, peptone, acetamide, urea, or L-aspartate. Slowly available carbon or nitrogen sources such as starch, cellulose, and peptone were beneficial to ammonium oxidation. In media containing sucrose as the sole carbon source and ammonium sulfate as the sole nitrogen source, nitrate formation was the most pronounced with sucrose present at a concentration of 12 g L^-1 and ammonium nitrogen present at a concentration of 2.438 mg mL% at the initial pH level of 7.5 and at 30℃.展开更多
Heterotrophic nitrifiers are bacteria that aerobically oxidize ammonia in the presence of organic carbon sources,which differs from autotrophic nitrifiers that extract energy from ammonia oxidation for cell metabolism...Heterotrophic nitrifiers are bacteria that aerobically oxidize ammonia in the presence of organic carbon sources,which differs from autotrophic nitrifiers that extract energy from ammonia oxidation for cell metabolism and growth.The physiological significance of heterotrophic ammonia oxidation remains unclear,even though this process has been known for decades.Here,we demonstrate that direct ammonia oxidation(Dirammox)—a heterotrophic ammonia oxidation process with dinitrogen(N)as the primary product—is associated with both redox balance and the electron transport chain in A/caligenes faecalis.Genetic and proteomic studies indicated that disruption of Dirammox genes(dnfA/dnfB/dnfC)induces a transient redox imbalance and perturbation in energy metabolism,further resulting in delayed growth.In addition,we found via biochemical and physiological studies that endogenous reactive oxygen species(ROS)enhance redox fluxes to ammonia oxidation,and the genetic disruption of cytochrome c peroxidase results in an increased flux of electrons to ammonia oxidation,producing N_(2) and N_(2)O.These unexpected findings provide a more thorough understanding of both the Dirammox process and the physiology of heterotrophic ammonia oxidation.展开更多
基金study was supported by the National Natural Science Foundation of China (NSFC-30371054)
文摘An ammonia-oxidizing strain of Penicillium sp., M25-22 which was isolated from chicken feces compost, was studied to make clear its characteristics of ammonium oxidation and provide references for its application in aerobic composting. In media containing （NH4）2SO4 at a concentration of 0.5 g 100 mL^-1, mycelium weight and utilization ratio of ammonium nitrogen increased markedly during the 1st 5 d, concentration of nitrate increased markedly from the 3rd to the 5th d and concentration of nitrite remained at a low level. The strain showed the ability to oxidize ammonium nitrogen growing in media containing glucose, sucrose, starch, or cellulose as the sole carbon source and to oxidize the negative trivalent nitrogen of ammonium sulfate, peptone, acetamide, urea, or L-aspartate. Slowly available carbon or nitrogen sources such as starch, cellulose, and peptone were beneficial to ammonium oxidation. In media containing sucrose as the sole carbon source and ammonium sulfate as the sole nitrogen source, nitrate formation was the most pronounced with sucrose present at a concentration of 12 g L^-1 and ammonium nitrogen present at a concentration of 2.438 mg mL% at the initial pH level of 7.5 and at 30℃.
基金supported by the grants from the National Key R&D Program of China(Grant No.2019YFA0905500).
文摘Heterotrophic nitrifiers are bacteria that aerobically oxidize ammonia in the presence of organic carbon sources,which differs from autotrophic nitrifiers that extract energy from ammonia oxidation for cell metabolism and growth.The physiological significance of heterotrophic ammonia oxidation remains unclear,even though this process has been known for decades.Here,we demonstrate that direct ammonia oxidation(Dirammox)—a heterotrophic ammonia oxidation process with dinitrogen(N)as the primary product—is associated with both redox balance and the electron transport chain in A/caligenes faecalis.Genetic and proteomic studies indicated that disruption of Dirammox genes(dnfA/dnfB/dnfC)induces a transient redox imbalance and perturbation in energy metabolism,further resulting in delayed growth.In addition,we found via biochemical and physiological studies that endogenous reactive oxygen species(ROS)enhance redox fluxes to ammonia oxidation,and the genetic disruption of cytochrome c peroxidase results in an increased flux of electrons to ammonia oxidation,producing N_(2) and N_(2)O.These unexpected findings provide a more thorough understanding of both the Dirammox process and the physiology of heterotrophic ammonia oxidation.
