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Metabolism of 4-chloro-2-nitrophenol in a gram-positive bacterium, Exiguobacterium sp. PMA.

Arora PK, Sharma A, Mehta R, Shenoy BD, Srivastava A, Singh VP - Microb. Cell Fact. (2012)

Bottom Line: The effects of different substrate concentrations and various inoculum sizes on degradation of 4C2NP were investigated.Exiguobacterium sp.The crude extract of 4C2NP-induced PMA cells contained enzymatic activity for 4C2NP reductase and 4C2AP dehalogenase, suggesting the involvement of these enzymes in the degradation of 4C2NP.

View Article: PubMed Central - HTML - PubMed

Affiliation: Microbial Type Culture Collection (MTCC) and Gene Bank, CSIR-Institute of Microbial Technology, Sec-39A, Chandigarh 1600036, India. arora484@gmail.com

ABSTRACT

Background: Chloronitrophenols (CNPs) are widely used in the synthesis of dyes, drugs and pesticides, and constitute a major group of environmental pollutants. 4-Chloro-2-nitrophenol (4C2NP) is an isomer of CNPs that has been detected in various industrial effluents. A number of physicochemical methods have been used for treatment of wastewater containing 4C2NP. These methods are not as effective as microbial degradation, however.

Results: A 4C2NP-degrading bacterium, Exiguobacterium sp. PMA, which uses 4C2NP as the sole carbon and energy source was isolated from a chemically-contaminated site in India. Exiguobacterium sp. PMA degraded 4C2NP with the release of stoichiometeric amounts of chloride and ammonium ions. The effects of different substrate concentrations and various inoculum sizes on degradation of 4C2NP were investigated. Exiguobacterium sp. PMA degraded 4C2NP up to a concentration of 0.6 mM. High performance liquid chromatography and gas chromatography-mass spectrometry identified 4-chloro-2-aminophenol (4C2AP) and 2-aminophenol (2AP) as possible metabolites of the 4C2NP degradation pathway. The crude extract of 4C2NP-induced PMA cells contained enzymatic activity for 4C2NP reductase and 4C2AP dehalogenase, suggesting the involvement of these enzymes in the degradation of 4C2NP. Microcosm studies using sterile and non-sterile soils spiked with 4C2NP were carried out to monitor the bioremediation potential of Exiguobacterium sp. PMA. The bioremediation of 4C2NP by Exiguobacterium sp. PMA was faster in non-sterilized soil than sterilized soil.

Conclusions: Our studies indicate that Exiguobacterium sp. PMA may be useful for the bioremediation of 4C2NP-contaminated sites. This is the first report of (i) the formation of 2AP in the 4C2NP degradation pathway by any bacterium and (iii) the bioremediation of 4C2NP by any bacterium.

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Microcosm studies. (a) Degradation of 4C2NP in sterile soil by Exiguobacterium sp. PMA. (b) Degradation of 4C2NP in non-sterile soil by Exiguobacterium sp. PMA, (c) Degradation of 4C2NP in control microcosm with sterile soil, (d) Degradation of 4C2NP in control microcosm with non-sterile soil.
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Figure 5: Microcosm studies. (a) Degradation of 4C2NP in sterile soil by Exiguobacterium sp. PMA. (b) Degradation of 4C2NP in non-sterile soil by Exiguobacterium sp. PMA, (c) Degradation of 4C2NP in control microcosm with sterile soil, (d) Degradation of 4C2NP in control microcosm with non-sterile soil.

Mentions: In the test microcosm with sterile soil, there was complete removal of 4C2NP by Exiguobacterium sp. PMA within 12 days (Figure 5a). No degradation was observed at initial two days after incubation. On the fourth days, 10% degradation was observed and degradation was 30% by sixth days. At eight days almost 56% degradation of 4C2NP was completed. The degradation was 76% by 10 days. Almost complete degradation of 4C2NP was observed at 12 days. In another test microcosm with non-sterile soil, complete 4C2NP depletion occurred within eight days (Figure 5b). However, in controls with sterile and non sterile soils, very low degradation was observed within 12 days (Figure 5c and5d).


Metabolism of 4-chloro-2-nitrophenol in a gram-positive bacterium, Exiguobacterium sp. PMA.

Arora PK, Sharma A, Mehta R, Shenoy BD, Srivastava A, Singh VP - Microb. Cell Fact. (2012)

Microcosm studies. (a) Degradation of 4C2NP in sterile soil by Exiguobacterium sp. PMA. (b) Degradation of 4C2NP in non-sterile soil by Exiguobacterium sp. PMA, (c) Degradation of 4C2NP in control microcosm with sterile soil, (d) Degradation of 4C2NP in control microcosm with non-sterile soil.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3539986&req=5

Figure 5: Microcosm studies. (a) Degradation of 4C2NP in sterile soil by Exiguobacterium sp. PMA. (b) Degradation of 4C2NP in non-sterile soil by Exiguobacterium sp. PMA, (c) Degradation of 4C2NP in control microcosm with sterile soil, (d) Degradation of 4C2NP in control microcosm with non-sterile soil.
Mentions: In the test microcosm with sterile soil, there was complete removal of 4C2NP by Exiguobacterium sp. PMA within 12 days (Figure 5a). No degradation was observed at initial two days after incubation. On the fourth days, 10% degradation was observed and degradation was 30% by sixth days. At eight days almost 56% degradation of 4C2NP was completed. The degradation was 76% by 10 days. Almost complete degradation of 4C2NP was observed at 12 days. In another test microcosm with non-sterile soil, complete 4C2NP depletion occurred within eight days (Figure 5b). However, in controls with sterile and non sterile soils, very low degradation was observed within 12 days (Figure 5c and5d).

Bottom Line: The effects of different substrate concentrations and various inoculum sizes on degradation of 4C2NP were investigated.Exiguobacterium sp.The crude extract of 4C2NP-induced PMA cells contained enzymatic activity for 4C2NP reductase and 4C2AP dehalogenase, suggesting the involvement of these enzymes in the degradation of 4C2NP.

View Article: PubMed Central - HTML - PubMed

Affiliation: Microbial Type Culture Collection (MTCC) and Gene Bank, CSIR-Institute of Microbial Technology, Sec-39A, Chandigarh 1600036, India. arora484@gmail.com

ABSTRACT

Background: Chloronitrophenols (CNPs) are widely used in the synthesis of dyes, drugs and pesticides, and constitute a major group of environmental pollutants. 4-Chloro-2-nitrophenol (4C2NP) is an isomer of CNPs that has been detected in various industrial effluents. A number of physicochemical methods have been used for treatment of wastewater containing 4C2NP. These methods are not as effective as microbial degradation, however.

Results: A 4C2NP-degrading bacterium, Exiguobacterium sp. PMA, which uses 4C2NP as the sole carbon and energy source was isolated from a chemically-contaminated site in India. Exiguobacterium sp. PMA degraded 4C2NP with the release of stoichiometeric amounts of chloride and ammonium ions. The effects of different substrate concentrations and various inoculum sizes on degradation of 4C2NP were investigated. Exiguobacterium sp. PMA degraded 4C2NP up to a concentration of 0.6 mM. High performance liquid chromatography and gas chromatography-mass spectrometry identified 4-chloro-2-aminophenol (4C2AP) and 2-aminophenol (2AP) as possible metabolites of the 4C2NP degradation pathway. The crude extract of 4C2NP-induced PMA cells contained enzymatic activity for 4C2NP reductase and 4C2AP dehalogenase, suggesting the involvement of these enzymes in the degradation of 4C2NP. Microcosm studies using sterile and non-sterile soils spiked with 4C2NP were carried out to monitor the bioremediation potential of Exiguobacterium sp. PMA. The bioremediation of 4C2NP by Exiguobacterium sp. PMA was faster in non-sterilized soil than sterilized soil.

Conclusions: Our studies indicate that Exiguobacterium sp. PMA may be useful for the bioremediation of 4C2NP-contaminated sites. This is the first report of (i) the formation of 2AP in the 4C2NP degradation pathway by any bacterium and (iii) the bioremediation of 4C2NP by any bacterium.

Show MeSH
Related in: MedlinePlus