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Jens Aamand - One of the best experts on this subject based on the ideXlab platform.
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microbial degradation of the benzonitrile herbicides Dichlobenil bromoxynil and ioxynil in soil and subsurface environments insights into degradation pathways persistent metabolites and involved degrader organisms
Environmental Pollution, 2008Co-Authors: Maria Sommer Holtze, Sebastian R Sorensen, Jan Sorensen, Jens AamandAbstract:The benzonitriles Dichlobenil, bromoxynil and ioxynil are important broad-spectrum or selective herbicides used in agriculture, orchards and public areas worldwide. The Dichlobenil metabolite 2,6-dichlorobenzamide is the most frequently encountered groundwater contaminant in Denmark, which suggests that the environmental fate of these three structurally related benzonitrile herbicides should be addressed in detail. This review summarises the current knowledge on microbial degradation of Dichlobenil, bromoxynil and ioxynil with particular focus on common features of degradation rates and pathways, accumulation of persistent metabolites and diversity of the involved degrader organisms.
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degradation of the herbicide Dichlobenil and its metabolite bam in soils and subsurface sediments
Journal of Contaminant Hydrology, 2007Co-Authors: Liselotte Clausen, Jens Aamand, Niels P Arildskov, Flemming Larsen, Hans-jørgen AlbrechtsenAbstract:The worldwide used herbicide Dichlobenil (2,6-dichlorobenzonitrile) has resulted in widespread presence of its metabolite 2,6-dichlorobenzamide (BAM) in surface water and groundwater. To evaluate the potential for natural attenuation of this BAM pollution in groundwater, we studied the degradation of BAM and Dichlobenil in 16 samples of clayey till, unconsolidated sand and limestone, including sediments from both oxidized and reduced conditions. The degradation of Dichlobenil occurred primarily in the upper few meters below surface, although Dichlobenil was strongly sorbed to these sediments. However, the degradation of Dichlobenil to BAM could not be correlated to either sorption, water chemistry, composition of soils or sediments. Degradation of Dichlobenil to BAM was limited (<2% degraded) in the deeper unsaturated zones, and no degradation was observed in aquifer sediments. This illustrates, that Dichlobenil transported to aquifers does not contribute to the BAM-contamination in aquifers. A small, but significant degradation of BAM was observed in the upper part of the unsaturated zones in sandy sediments, but no degradation was observed in the clayey till sediment or in the deeper unsaturated zones. The insignificant degradation of BAM in aquifer systems shows that BAM pollution detected in aquifers will appear for a long time; and consequently the potential for natural attenuation of BAM in aquifer systems is limited.
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Microbial degradation pathways of the herbicide Dichlobenil in soils with different history of Dichlobenil-exposure
Environmental Pollution, 2007Co-Authors: Maria Sommer Holtze, Hans Christian Bruun Hansen, René K. Juhler, Jan Tind Sørensen, Jens AamandAbstract:This is the first detailed study of metabolite production during degradation of the herbicide 2,6-dichlorobenzonitrile (Dichlobenil). Degradation of Dichlobenil and three potential metabolites: 2,6-dichlorobenzamide (BAM), 2,6-dichlorobenzoic acid (2,6-DCBA) and ortho-chlorobenzamide (OBAM) was studied in soils either previously exposed or not exposed to Dichlobenil using a newly developed HPLC method. Dichlobenil was degraded in all four soils; BAM and 2,6-DCBA were only degraded in soils previously exposed to Dichlobenil (100% within 35-56 days and 85-100% in 56 days, respectively), and OBAM in all four soils (25-33% removal in 48 days). BAM produced from Dichlobenil was either hydrolyzed to 2,6-DCBA or dechlorinated to OBAM, which was further hydrolyzed to ortho-chlorobenzoic acid. BAM was rapidly mineralized in previously exposed soils only. All potential metabolites and the finding that BAM was a dead-end metabolite of Dichlobenil in soils not previously exposed to Dichlobenil needs to be included in risk assessments of the use of Dichlobenil.
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Degradation of the herbicide Dichlobenil and its metabolite BAM in soils and subsurface sediments.
Journal of Contaminant Hydrology, 2007Co-Authors: Liselotte Clausen, Jens Aamand, Niels P Arildskov, Flemming Larsen, Hans-jørgen AlbrechtsenAbstract:The worldwide used herbicide Dichlobenil (2,6-dichlorobenzonitrile) has resulted in widespread presence of its metabolite 2,6-dichlorobenzamide (BAM) in surface water and groundwater. To evaluate the potential for natural attenuation of this BAM pollution in groundwater, we studied the degradation of BAM and Dichlobenil in 16 samples of clayey till, unconsolidated sand and limestone, including sediments from both oxidized and reduced conditions. The degradation of Dichlobenil occurred primarily in the upper few meters below surface, although Dichlobenil was strongly sorbed to these sediments. However, the degradation of Dichlobenil to BAM could not be correlated to either sorption, water chemistry, composition of soils or sediments. Degradation of Dichlobenil to BAM was limited (
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Biostimulation and enrichment of 2,6-dichlorobenzamide-mineralising soil bacterial communities from Dichlobenil-exposed soil
Soil Biology and Biochemistry, 2007Co-Authors: Maria Sommer Holtze, Sebastian R Sorensen, Hans Christian Bruun Hansen, Jan Tind Sørensen, Jens AamandAbstract:Eleven enrichment cultures of 2,6-dichlorobenzamide (BAM)-mineralising bacteria from a Dichlobenil-exposed soil were enriched using three different media. Ten of the enriched mixed cultures had stimulated BAM mineralisation only in the presence of supplementary carbon and were able to utilise BAM as the sole nitrogen source, while only one was able to utilise BAM as the sole source of both carbon and nitrogen. Cultivation and DNA-based analysis of the mixed cultures suggested that different bacterial populations were stimulated by the three strategies. Our findings indicate that natural BAM-mineralising populations capable of using BAM as a source of nitrogen can be readily stimulated, enriched and maintained following sub-culturing from Dichlobenil-treated soils by adding an alternative carbon source.
Hans-jørgen Albrechtsen - One of the best experts on this subject based on the ideXlab platform.
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degradation of the herbicide Dichlobenil and its metabolite bam in soils and subsurface sediments
Journal of Contaminant Hydrology, 2007Co-Authors: Liselotte Clausen, Jens Aamand, Niels P Arildskov, Flemming Larsen, Hans-jørgen AlbrechtsenAbstract:The worldwide used herbicide Dichlobenil (2,6-dichlorobenzonitrile) has resulted in widespread presence of its metabolite 2,6-dichlorobenzamide (BAM) in surface water and groundwater. To evaluate the potential for natural attenuation of this BAM pollution in groundwater, we studied the degradation of BAM and Dichlobenil in 16 samples of clayey till, unconsolidated sand and limestone, including sediments from both oxidized and reduced conditions. The degradation of Dichlobenil occurred primarily in the upper few meters below surface, although Dichlobenil was strongly sorbed to these sediments. However, the degradation of Dichlobenil to BAM could not be correlated to either sorption, water chemistry, composition of soils or sediments. Degradation of Dichlobenil to BAM was limited (<2% degraded) in the deeper unsaturated zones, and no degradation was observed in aquifer sediments. This illustrates, that Dichlobenil transported to aquifers does not contribute to the BAM-contamination in aquifers. A small, but significant degradation of BAM was observed in the upper part of the unsaturated zones in sandy sediments, but no degradation was observed in the clayey till sediment or in the deeper unsaturated zones. The insignificant degradation of BAM in aquifer systems shows that BAM pollution detected in aquifers will appear for a long time; and consequently the potential for natural attenuation of BAM in aquifer systems is limited.
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Degradation of the herbicide Dichlobenil and its metabolite BAM in soils and subsurface sediments.
Journal of Contaminant Hydrology, 2007Co-Authors: Liselotte Clausen, Jens Aamand, Niels P Arildskov, Flemming Larsen, Hans-jørgen AlbrechtsenAbstract:The worldwide used herbicide Dichlobenil (2,6-dichlorobenzonitrile) has resulted in widespread presence of its metabolite 2,6-dichlorobenzamide (BAM) in surface water and groundwater. To evaluate the potential for natural attenuation of this BAM pollution in groundwater, we studied the degradation of BAM and Dichlobenil in 16 samples of clayey till, unconsolidated sand and limestone, including sediments from both oxidized and reduced conditions. The degradation of Dichlobenil occurred primarily in the upper few meters below surface, although Dichlobenil was strongly sorbed to these sediments. However, the degradation of Dichlobenil to BAM could not be correlated to either sorption, water chemistry, composition of soils or sediments. Degradation of Dichlobenil to BAM was limited (
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Sorption of the herbicide Dichlobenil and the metabolite 2,6-dichlorobenzamide on soils and aquifer sediments.
Environmental Science & Technology, 2004Co-Authors: Liselotte Clausen, Flemming Larsen, Hans-jørgen AlbrechtsenAbstract:The worldwide used herbicide Dichlobenil (2,6-dichlorobenzonitrile) has resulted in widespread presence of its metabolite 2,6-dichlorobenzamide (BAM) in pore- and groundwater. To evaluate the transport of these compounds we studied the sorption of Dichlobenil and BAM in 22 sediment samples of clayey till, sand, and limestone including sediments exhibiting varying oxidation states. Dichlobenil sorbed to all investigated sediments, with a high sorption in topsoils (Kd = 7.4−17.4 L kg-1) and clayey till sediments (Kd = 2.7−126 L kg-1). The sorption of the polar metabolite BAM was much lower than the sorption of Dichlobenil but followed the same tendency with the highest sorption in the topsoils (Kd = 0.24−0.66 L kg-1) and in the clayey till sediments (Kd = 0.10−0.93 L kg-1). The sorption of both compounds was significantly higher (2−47 times) in the unoxidized (reduced) clayey till than in the weathered (oxidized) clayey till. Such a difference in sorption capacity could neither be explained by a higher orga...
Maria Sommer Holtze - One of the best experts on this subject based on the ideXlab platform.
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microbial degradation of the benzonitrile herbicides Dichlobenil bromoxynil and ioxynil in soil and subsurface environments insights into degradation pathways persistent metabolites and involved degrader organisms
Environmental Pollution, 2008Co-Authors: Maria Sommer Holtze, Sebastian R Sorensen, Jan Sorensen, Jens AamandAbstract:The benzonitriles Dichlobenil, bromoxynil and ioxynil are important broad-spectrum or selective herbicides used in agriculture, orchards and public areas worldwide. The Dichlobenil metabolite 2,6-dichlorobenzamide is the most frequently encountered groundwater contaminant in Denmark, which suggests that the environmental fate of these three structurally related benzonitrile herbicides should be addressed in detail. This review summarises the current knowledge on microbial degradation of Dichlobenil, bromoxynil and ioxynil with particular focus on common features of degradation rates and pathways, accumulation of persistent metabolites and diversity of the involved degrader organisms.
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Microbial degradation pathways of the herbicide Dichlobenil in soils with different history of Dichlobenil-exposure
Environmental Pollution, 2007Co-Authors: Maria Sommer Holtze, Hans Christian Bruun Hansen, René K. Juhler, Jan Tind Sørensen, Jens AamandAbstract:This is the first detailed study of metabolite production during degradation of the herbicide 2,6-dichlorobenzonitrile (Dichlobenil). Degradation of Dichlobenil and three potential metabolites: 2,6-dichlorobenzamide (BAM), 2,6-dichlorobenzoic acid (2,6-DCBA) and ortho-chlorobenzamide (OBAM) was studied in soils either previously exposed or not exposed to Dichlobenil using a newly developed HPLC method. Dichlobenil was degraded in all four soils; BAM and 2,6-DCBA were only degraded in soils previously exposed to Dichlobenil (100% within 35-56 days and 85-100% in 56 days, respectively), and OBAM in all four soils (25-33% removal in 48 days). BAM produced from Dichlobenil was either hydrolyzed to 2,6-DCBA or dechlorinated to OBAM, which was further hydrolyzed to ortho-chlorobenzoic acid. BAM was rapidly mineralized in previously exposed soils only. All potential metabolites and the finding that BAM was a dead-end metabolite of Dichlobenil in soils not previously exposed to Dichlobenil needs to be included in risk assessments of the use of Dichlobenil.
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Biostimulation and enrichment of 2,6-dichlorobenzamide-mineralising soil bacterial communities from Dichlobenil-exposed soil
Soil Biology and Biochemistry, 2007Co-Authors: Maria Sommer Holtze, Sebastian R Sorensen, Hans Christian Bruun Hansen, Jan Tind Sørensen, Jens AamandAbstract:Eleven enrichment cultures of 2,6-dichlorobenzamide (BAM)-mineralising bacteria from a Dichlobenil-exposed soil were enriched using three different media. Ten of the enriched mixed cultures had stimulated BAM mineralisation only in the presence of supplementary carbon and were able to utilise BAM as the sole nitrogen source, while only one was able to utilise BAM as the sole source of both carbon and nitrogen. Cultivation and DNA-based analysis of the mixed cultures suggested that different bacterial populations were stimulated by the three strategies. Our findings indicate that natural BAM-mineralising populations capable of using BAM as a source of nitrogen can be readily stimulated, enriched and maintained following sub-culturing from Dichlobenil-treated soils by adding an alternative carbon source.
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Transformation of the herbicide 2,6-dichlorobenzonitrile to the persistent metabolite 2,6-dichlorobenzamide (BAM) by soil bacteria known to harbour nitrile hydratase or nitrilase
Biodegradation, 2006Co-Authors: Maria Sommer Holtze, Hans Christian B. Hansen, Jan Sorensen, Jens AamandAbstract:In soil the herbicide 2,6-dichlorobenzonitrile (Dichlobenil) is degraded to the persistent metabolite 2,6-dichlorobenzamide (BAM) which has been detected in 19% of samples taken from Danish groundwater. We tested if common soil bacteria harbouring nitrile-degrading enzymes, nitrile hydratases or nitrilases, were able to degrade Dichlobenil in vitro . We showed that several strains degraded Dichlobenil stoichiometrically to BAM in 1.5–6.0 days; formation of the amide intermediate thus showed nitrile hydratase rather than nitrilase activity, which would result in formation of 2,6-dichlorobenzoic acid. The non-halogenated␣analogue benzonitrile was also degraded, but here the benzamide intermediate accumulated only transiently showing nitrile hydratase followed by amidase activity. We conclude that a potential for Dichlobenil degradation to BAM is found commonly in soil bacteria, whereas further degradation of the BAM intermediate could not be demonstrated.
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Degradation and Mineralization of Nanomolar Concentrations of the Herbicide Dichlobenil and Its Persistent Metabolite 2,6-Dichlorobenzamide by Aminobacter spp. Isolated from Dichlobenil-Treated Soils
Applied and Environmental Microbiology, 2006Co-Authors: Sebastian R Sorensen, Maria Sommer Holtze, Allan Simonsen, Jens AamandAbstract:Each year, millions of tons of xenobiotic compounds are applied globally as pesticides in agricultural production and in consolidated urban areas, along railways and roads and within farmyards. As an outcome of this extensive environmental input, natural water in rivers, lakes, and aquifers has been contaminated with trace amounts of pesticide residues. In Denmark, where more than 99% of the drinking water originates from groundwater, the detection of pesticide residues above the European Commission (EC) threshold limit of 0.1 μg liter−1 has resulted in the costly closure of numerous groundwater abstraction wells (29). Not only are the pesticides themselves monitored, but selected stable metabolites are also included, and often these are detected more frequently than the pesticide itself (3). The most commonly encountered pesticide residue in Danish groundwater is 2,6-dichlorobenzamide (BAM). BAM is a metabolite produced from partial degradation of the benzonitrile herbicide 2,6-dichlorobenzonitrile (Dichlobenil) (1, 9, 16) and is often highly persistent in the environment. Dichlobenil is a broad-spectrum herbicide mostly used on nonagricultural areas, as well as in plant nurseries and fruit orchards. This herbicide was banned for use in Denmark in 1997, but BAM is still the main pesticide residue in Danish groundwater, with 19.7% of the abstraction wells analyzed in 2003 having detectable BAM concentrations and 8.1% of the wells containing BAM concentrations exceeding the EC threshold limit of 0.1 μg liter−1 for drinking water (3). Similar results were reported in 2003 in a monitoring program from Sweden (13), and BAM has additionally been detected in groundwater in The Netherlands, Germany, and Italy (18, 42, 44). A potential for partial degradation of the herbicide Dichlobenil to BAM has been measured in various soils and subsurface sediments, with estimated half-lives ranging from 106 to 2,079 days (6, 8, 16, 41). Also, 2,6-dichlorobenzoic acid, another known metabolite from Dichlobenil, has been measured in Dichlobenil-treated soils (8, 24) and in groundwater samples (3, 18). Two additional metabolites, ortho-chlorobenzamide and ortho-chlorobenzoic acid, have been detected in laboratory experiments with Dichlobenil-treated soils (8). The metabolite BAM appears to be much more persistent than Dichlobenil itself, and several studies have reported no apparent degradation of BAM in soils (1, 6, 8, 16, 40, 41), aquifer sediments (2, 6, 36, 37), or bacterial isolates (9, 43). Little is therefore known about the environmental degradation of BAM. We are interested in using degradative bacteria for remediation of groundwater contaminated with low concentrations of BAM, and we therefore recently initiated a large-scale screening of Dichlobenil-treated areas to locate soils capable of rapid mineralization of BAM (10, 25). These efforts have pinpointed 6 soils that have a potential for mineralization of [ring-U-14C]BAM to 14CO2, out of a total of 79 samples screened for mineralization activity, obtained from 39 different Danish locations previously exposed to Dichlobenil. One of the soils with a potential for BAM mineralization but with no evident Dichlobenil mineralization was recently used to enrich and isolate a BAM-mineralizing bacterium identified as an Aminobacter isolate, designated strain ASI1 (25). A second soil sampled from the courtyard of a former plant nursery located above a BAM-contaminated aquifer had a unique ability to mineralize both BAM and [ring-U-14C]Dichlobenil to 14CO2 (25), and we later succeeded in obtaining stable BAM-mineralizing enrichment cultures (10), but isolation of degradative bacteria was not achieved. In this study we revived one of these enrichment cultures and isolated a BAM- and Dichlobenil-mineralizing Aminobacter sp. strain (designated strain MSH1). This strain is closely related to our BAM-mineralizing Aminobacter sp. strain ASI1, and these two strains along with selected Aminobacter type strains were compared with regard to their taxonomy, degradative capacity toward Dichlobenil and related compounds, and ability to degrade and mineralize low concentrations of BAM and Dichlobenil.
Liselotte Clausen - One of the best experts on this subject based on the ideXlab platform.
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degradation of the herbicide Dichlobenil and its metabolite bam in soils and subsurface sediments
Journal of Contaminant Hydrology, 2007Co-Authors: Liselotte Clausen, Jens Aamand, Niels P Arildskov, Flemming Larsen, Hans-jørgen AlbrechtsenAbstract:The worldwide used herbicide Dichlobenil (2,6-dichlorobenzonitrile) has resulted in widespread presence of its metabolite 2,6-dichlorobenzamide (BAM) in surface water and groundwater. To evaluate the potential for natural attenuation of this BAM pollution in groundwater, we studied the degradation of BAM and Dichlobenil in 16 samples of clayey till, unconsolidated sand and limestone, including sediments from both oxidized and reduced conditions. The degradation of Dichlobenil occurred primarily in the upper few meters below surface, although Dichlobenil was strongly sorbed to these sediments. However, the degradation of Dichlobenil to BAM could not be correlated to either sorption, water chemistry, composition of soils or sediments. Degradation of Dichlobenil to BAM was limited (<2% degraded) in the deeper unsaturated zones, and no degradation was observed in aquifer sediments. This illustrates, that Dichlobenil transported to aquifers does not contribute to the BAM-contamination in aquifers. A small, but significant degradation of BAM was observed in the upper part of the unsaturated zones in sandy sediments, but no degradation was observed in the clayey till sediment or in the deeper unsaturated zones. The insignificant degradation of BAM in aquifer systems shows that BAM pollution detected in aquifers will appear for a long time; and consequently the potential for natural attenuation of BAM in aquifer systems is limited.
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Degradation of the herbicide Dichlobenil and its metabolite BAM in soils and subsurface sediments.
Journal of Contaminant Hydrology, 2007Co-Authors: Liselotte Clausen, Jens Aamand, Niels P Arildskov, Flemming Larsen, Hans-jørgen AlbrechtsenAbstract:The worldwide used herbicide Dichlobenil (2,6-dichlorobenzonitrile) has resulted in widespread presence of its metabolite 2,6-dichlorobenzamide (BAM) in surface water and groundwater. To evaluate the potential for natural attenuation of this BAM pollution in groundwater, we studied the degradation of BAM and Dichlobenil in 16 samples of clayey till, unconsolidated sand and limestone, including sediments from both oxidized and reduced conditions. The degradation of Dichlobenil occurred primarily in the upper few meters below surface, although Dichlobenil was strongly sorbed to these sediments. However, the degradation of Dichlobenil to BAM could not be correlated to either sorption, water chemistry, composition of soils or sediments. Degradation of Dichlobenil to BAM was limited (
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Sorption of the herbicide Dichlobenil and the metabolite 2,6-dichlorobenzamide on soils and aquifer sediments.
Environmental Science & Technology, 2004Co-Authors: Liselotte Clausen, Flemming Larsen, Hans-jørgen AlbrechtsenAbstract:The worldwide used herbicide Dichlobenil (2,6-dichlorobenzonitrile) has resulted in widespread presence of its metabolite 2,6-dichlorobenzamide (BAM) in pore- and groundwater. To evaluate the transport of these compounds we studied the sorption of Dichlobenil and BAM in 22 sediment samples of clayey till, sand, and limestone including sediments exhibiting varying oxidation states. Dichlobenil sorbed to all investigated sediments, with a high sorption in topsoils (Kd = 7.4−17.4 L kg-1) and clayey till sediments (Kd = 2.7−126 L kg-1). The sorption of the polar metabolite BAM was much lower than the sorption of Dichlobenil but followed the same tendency with the highest sorption in the topsoils (Kd = 0.24−0.66 L kg-1) and in the clayey till sediments (Kd = 0.10−0.93 L kg-1). The sorption of both compounds was significantly higher (2−47 times) in the unoxidized (reduced) clayey till than in the weathered (oxidized) clayey till. Such a difference in sorption capacity could neither be explained by a higher orga...
Roberto P Revoltella - One of the best experts on this subject based on the ideXlab platform.
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human cord blood cd133 stem cells transplanted to nod scid mice provide conditions for regeneration of olfactory neuroepithelium after permanent damage induced by Dichlobenil
Stem Cells, 2009Co-Authors: Valeria Franceschini, Simone Bettini, Simone Pifferi, Alfredo Rosellini, Anna Menini, Ricardo Saccardi, Emanuela Ognio, Rosemary Jeffery, Richard Poulsom, Roberto P RevoltellaAbstract:The herbicide Dichlobenil selectively causes necrosis of the dorsomedial part of olfactory neuroepithelium (NE) with permanent damage to the underlying mucosa, whereas the lateral part of the olfactory region and the nasal respiratory mucosa remain undamaged. We investigated here whether human umbilical cord blood CD133 1 stem cells (HSC) injected intravenously to nod-scid mice pretreated with Dichlobenil may engraft the olfactory mucosa and contribute to the regeneration of the damaged NE. We tested HLA-DQa1 DNA and three human microsatellites (Combined DNA Index System) as indicators of engrafted cells, finding polymerase chain reaction evidence of chimaerism in various tissues of the host, including the olfactory mucosa and bulb, at 7 and 31 days following HSC transplantation. Histology, immunohistochemistry, and lectin staining revealed the morphological recovery of the dorsomedial region of the NE in Dichlobenil-treated mice that received HSC, contrasting with the lack of regeneration in similarly injured areas as these remained damaged in control nontransplanted mice. FISH analysis, to detect human genomic sequences from different chromosomes, confirmed persistent engraftment of the regenerating olfactory area with chimeric cells. Electro-olfactograms in response to odorants, to test the functionality of the olfactory NE, confirmed the functional damage of the dorsomedial area in Dichlobenil-treated mice and the functional recovery of the same area in transplanted mice. These findings support the concept that transplanted HSC migrating to the damaged olfactory area provide conditions facilitating the recovery from olfactory receptor cell loss. STEM CELLS 2009;27:825–835
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Human cord blood CD133+ stem cells transplanted to nod-scid mice provide conditions for regeneration of olfactory neuroepithelium after permanent damage induced by Dichlobenil.
STEM CELLS, 2009Co-Authors: Valeria Franceschini, Simone Bettini, Simone Pifferi, Alfredo Rosellini, Anna Menini, Ricardo Saccardi, Emanuela Ognio, Rosemary Jeffery, Richard Poulsom, Roberto P RevoltellaAbstract:The herbicide Dichlobenil selectively causes necrosis of the dorsomedial part of olfactory neuroepithelium (NE) with permanent damage to the underlying mucosa, whereas the lateral part of the olfactory region and the nasal respiratory mucosa remain undamaged. We investigated here whether human umbilical cord blood CD133 1 stem cells (HSC) injected intravenously to nod-scid mice pretreated with Dichlobenil may engraft the olfactory mucosa and contribute to the regeneration of the damaged NE. We tested HLA-DQa1 DNA and three human microsatellites (Combined DNA Index System) as indicators of engrafted cells, finding polymerase chain reaction evidence of chimaerism in various tissues of the host, including the olfactory mucosa and bulb, at 7 and 31 days following HSC transplantation. Histology, immunohistochemistry, and lectin staining revealed the morphological recovery of the dorsomedial region of the NE in Dichlobenil-treated mice that received HSC, contrasting with the lack of regeneration in similarly injured areas as these remained damaged in control nontransplanted mice. FISH analysis, to detect human genomic sequences from different chromosomes, confirmed persistent engraftment of the regenerating olfactory area with chimeric cells. Electro-olfactograms in response to odorants, to test the functionality of the olfactory NE, confirmed the functional damage of the dorsomedial area in Dichlobenil-treated mice and the functional recovery of the same area in transplanted mice. These findings support the concept that transplanted HSC migrating to the damaged olfactory area provide conditions facilitating the recovery from olfactory receptor cell loss. STEM CELLS 2009;27:825–835