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Thiomonas sp. CB2 is able to degrade urea and promote toxic metal precipitation in acid mine drainage waters supplemented with urea.

Farasin J, Andres J, Casiot C, Barbe V, Faerber J, Halter D, Heintz D, Koechler S, Lièvremont D, Lugan R, Marchal M, Plewniak F, Seby F, Bertin PN, Arsène-Ploetze F - Front Microbiol (2015)

Bottom Line: The urease activity of Thiomonas sp.In AMD water supplemented with urea, the degradation of urea promotes iron, aluminum and arsenic precipitation.Our data show that ureC was expressed in situ, which suggests that the ability to degrade urea may be expressed in some Thiomonas strains in AMD, and that this urease activity may contribute to their survival in contaminated environments.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire Génétique Moléculaire, Génomique et Microbiologie, UMR7156, Université de Strasbourg - Centre National de la Recherche Scientifique, Institut de Botanique Strasbourg, France.

ABSTRACT
The acid mine drainage (AMD) in Carnoulès (France) is characterized by the presence of toxic metals such as arsenic. Several bacterial strains belonging to the Thiomonas genus, which were isolated from this AMD, are able to withstand these conditions. Their genomes carry several genomic islands (GEIs), which are known to be potentially advantageous in some particular ecological niches. This study focused on the role of the "urea island" present in the Thiomonas CB2 strain, which carry the genes involved in urea degradation processes. First, genomic comparisons showed that the genome of Thiomonas sp. CB2, which is able to degrade urea, contains a urea genomic island which is incomplete in the genome of other strains showing no urease activity. The urease activity of Thiomonas sp. CB2 enabled this bacterium to maintain a neutral pH in cell cultures in vitro and prevented the occurrence of cell death during the growth of the bacterium in a chemically defined medium. In AMD water supplemented with urea, the degradation of urea promotes iron, aluminum and arsenic precipitation. Our data show that ureC was expressed in situ, which suggests that the ability to degrade urea may be expressed in some Thiomonas strains in AMD, and that this urease activity may contribute to their survival in contaminated environments.

No MeSH data available.


Related in: MedlinePlus

Thiomonas urea degradation activity promotes Fe(II) oxidation/precipitation in AMD-impacted water supplemented with urea. K12, 3As, and CB2 were incubated at an initial OD600nm of 0.2 – 0.3 in AMD-impacted water in the absence and presence of 1 g.L−1 urea. (A) The medium supplemented with urea and CB2 acquired an orange color with time, which did not occur with 3As or K12. (B) Orange precipitate detected after centrifuging 4-day cell cultures of CB2 in AMD-impacted water supplemented or not with 1 g.L−1 urea. (C) Kinetics of Fe(II) oxidation/precipitation. Fe(II) oxidation/precipitation is expressed as the difference between the Fe(II) concentrations measured in the soluble fractions of the non-inoculated and inoculated samples. The dotted line gives the 5% confidence interval of each of the regression lines, computed with the MATLAB fitlm command. (D) Effects of urease activity on the formation of orange precipitate in the AMD-impacted water. AMD-impacted water was supplemented with 10 U of purified urease in the presence and absence of 1 g.L−1 urea. As an additional control, urease was heat-inactivated for 5 min at 95°C.
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Figure 7: Thiomonas urea degradation activity promotes Fe(II) oxidation/precipitation in AMD-impacted water supplemented with urea. K12, 3As, and CB2 were incubated at an initial OD600nm of 0.2 – 0.3 in AMD-impacted water in the absence and presence of 1 g.L−1 urea. (A) The medium supplemented with urea and CB2 acquired an orange color with time, which did not occur with 3As or K12. (B) Orange precipitate detected after centrifuging 4-day cell cultures of CB2 in AMD-impacted water supplemented or not with 1 g.L−1 urea. (C) Kinetics of Fe(II) oxidation/precipitation. Fe(II) oxidation/precipitation is expressed as the difference between the Fe(II) concentrations measured in the soluble fractions of the non-inoculated and inoculated samples. The dotted line gives the 5% confidence interval of each of the regression lines, computed with the MATLAB fitlm command. (D) Effects of urease activity on the formation of orange precipitate in the AMD-impacted water. AMD-impacted water was supplemented with 10 U of purified urease in the presence and absence of 1 g.L−1 urea. As an additional control, urease was heat-inactivated for 5 min at 95°C.

Mentions: An orange precipitate accumulated during the experiments with CB2 in AMD-impacted water in the presence of urea, which was not observed in samples where no urea degradation activity was possible (Figures 7A,B). To test whether this precipitate was correlated with urease activity, purified urease and urea were added to sterile AMD-impacted water. A substantial orange precipitate was observed when both urease and urea were added, whereas no precipitate occurred when only urea was added, and less precipitate when urease was heat-inactivated (Figure 7D). The presence of this orange material suggested that Fe was precipitated when either urease or bacteria with urea degradation activity were present in the AMD water supplemented with urea. A covariance analysis was performed with MATLAB R2014a (using the aoctool and multcompare commands) on the quantity of soluble Fe(II) measured in the dissolved phase vs. time. This analysis showed that the rate of Fe(II) oxidation and subsequent Fe(III) precipitation was significantly higher (p < 0.01) in the case of CB2 grown with urea than in that of the other cell cultures tested (CB2 without urea and 3As or K12 with and without urea) (Figure 7C). CB2 is not able to oxidize ferrous iron in synthetic medium, (data not shown), which is consistent with the finding that its genome lack any detectable genes normally associated with Fe(II) oxidation. This is also true in the case of other Thiomonas strains (Slyemi et al., 2011). The iron precipitation observed here in AMD-impacted water in the presence of urea was therefore probably due to abiotic oxidation. In view of the dependence of the Fe(II) oxidation rate on the pH in natural waters (Sigg et al., 2006), the iron oxidation observed here may have been at least partly due to the increase in the pH observed under our experimental conditions as the result of urea degradation activity.


Thiomonas sp. CB2 is able to degrade urea and promote toxic metal precipitation in acid mine drainage waters supplemented with urea.

Farasin J, Andres J, Casiot C, Barbe V, Faerber J, Halter D, Heintz D, Koechler S, Lièvremont D, Lugan R, Marchal M, Plewniak F, Seby F, Bertin PN, Arsène-Ploetze F - Front Microbiol (2015)

Thiomonas urea degradation activity promotes Fe(II) oxidation/precipitation in AMD-impacted water supplemented with urea. K12, 3As, and CB2 were incubated at an initial OD600nm of 0.2 – 0.3 in AMD-impacted water in the absence and presence of 1 g.L−1 urea. (A) The medium supplemented with urea and CB2 acquired an orange color with time, which did not occur with 3As or K12. (B) Orange precipitate detected after centrifuging 4-day cell cultures of CB2 in AMD-impacted water supplemented or not with 1 g.L−1 urea. (C) Kinetics of Fe(II) oxidation/precipitation. Fe(II) oxidation/precipitation is expressed as the difference between the Fe(II) concentrations measured in the soluble fractions of the non-inoculated and inoculated samples. The dotted line gives the 5% confidence interval of each of the regression lines, computed with the MATLAB fitlm command. (D) Effects of urease activity on the formation of orange precipitate in the AMD-impacted water. AMD-impacted water was supplemented with 10 U of purified urease in the presence and absence of 1 g.L−1 urea. As an additional control, urease was heat-inactivated for 5 min at 95°C.
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Related In: Results  -  Collection

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Figure 7: Thiomonas urea degradation activity promotes Fe(II) oxidation/precipitation in AMD-impacted water supplemented with urea. K12, 3As, and CB2 were incubated at an initial OD600nm of 0.2 – 0.3 in AMD-impacted water in the absence and presence of 1 g.L−1 urea. (A) The medium supplemented with urea and CB2 acquired an orange color with time, which did not occur with 3As or K12. (B) Orange precipitate detected after centrifuging 4-day cell cultures of CB2 in AMD-impacted water supplemented or not with 1 g.L−1 urea. (C) Kinetics of Fe(II) oxidation/precipitation. Fe(II) oxidation/precipitation is expressed as the difference between the Fe(II) concentrations measured in the soluble fractions of the non-inoculated and inoculated samples. The dotted line gives the 5% confidence interval of each of the regression lines, computed with the MATLAB fitlm command. (D) Effects of urease activity on the formation of orange precipitate in the AMD-impacted water. AMD-impacted water was supplemented with 10 U of purified urease in the presence and absence of 1 g.L−1 urea. As an additional control, urease was heat-inactivated for 5 min at 95°C.
Mentions: An orange precipitate accumulated during the experiments with CB2 in AMD-impacted water in the presence of urea, which was not observed in samples where no urea degradation activity was possible (Figures 7A,B). To test whether this precipitate was correlated with urease activity, purified urease and urea were added to sterile AMD-impacted water. A substantial orange precipitate was observed when both urease and urea were added, whereas no precipitate occurred when only urea was added, and less precipitate when urease was heat-inactivated (Figure 7D). The presence of this orange material suggested that Fe was precipitated when either urease or bacteria with urea degradation activity were present in the AMD water supplemented with urea. A covariance analysis was performed with MATLAB R2014a (using the aoctool and multcompare commands) on the quantity of soluble Fe(II) measured in the dissolved phase vs. time. This analysis showed that the rate of Fe(II) oxidation and subsequent Fe(III) precipitation was significantly higher (p < 0.01) in the case of CB2 grown with urea than in that of the other cell cultures tested (CB2 without urea and 3As or K12 with and without urea) (Figure 7C). CB2 is not able to oxidize ferrous iron in synthetic medium, (data not shown), which is consistent with the finding that its genome lack any detectable genes normally associated with Fe(II) oxidation. This is also true in the case of other Thiomonas strains (Slyemi et al., 2011). The iron precipitation observed here in AMD-impacted water in the presence of urea was therefore probably due to abiotic oxidation. In view of the dependence of the Fe(II) oxidation rate on the pH in natural waters (Sigg et al., 2006), the iron oxidation observed here may have been at least partly due to the increase in the pH observed under our experimental conditions as the result of urea degradation activity.

Bottom Line: The urease activity of Thiomonas sp.In AMD water supplemented with urea, the degradation of urea promotes iron, aluminum and arsenic precipitation.Our data show that ureC was expressed in situ, which suggests that the ability to degrade urea may be expressed in some Thiomonas strains in AMD, and that this urease activity may contribute to their survival in contaminated environments.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire Génétique Moléculaire, Génomique et Microbiologie, UMR7156, Université de Strasbourg - Centre National de la Recherche Scientifique, Institut de Botanique Strasbourg, France.

ABSTRACT
The acid mine drainage (AMD) in Carnoulès (France) is characterized by the presence of toxic metals such as arsenic. Several bacterial strains belonging to the Thiomonas genus, which were isolated from this AMD, are able to withstand these conditions. Their genomes carry several genomic islands (GEIs), which are known to be potentially advantageous in some particular ecological niches. This study focused on the role of the "urea island" present in the Thiomonas CB2 strain, which carry the genes involved in urea degradation processes. First, genomic comparisons showed that the genome of Thiomonas sp. CB2, which is able to degrade urea, contains a urea genomic island which is incomplete in the genome of other strains showing no urease activity. The urease activity of Thiomonas sp. CB2 enabled this bacterium to maintain a neutral pH in cell cultures in vitro and prevented the occurrence of cell death during the growth of the bacterium in a chemically defined medium. In AMD water supplemented with urea, the degradation of urea promotes iron, aluminum and arsenic precipitation. Our data show that ureC was expressed in situ, which suggests that the ability to degrade urea may be expressed in some Thiomonas strains in AMD, and that this urease activity may contribute to their survival in contaminated environments.

No MeSH data available.


Related in: MedlinePlus