Isotope
Fractionation Pinpoints Membrane Permeability
as a Barrier to Atrazine Biodegradation in Gram-negative Polaromonas sp. Nea‑C
Version 4 2019-03-02, 14:13
Version 3 2019-01-10, 11:13
Version 2 2018-03-23, 12:09
Version 1 2018-03-23, 12:03
Posted on 2019-03-02 - 14:13
Biodegradation
of persistent pesticides like atrazine often stalls
at low concentrations in the environment. While mass transfer does
not limit atrazine degradation by the Gram-positive Arthrobacter aurescens TC1 at high concentrations
(>1 mg/L), evidence of bioavailability limitations is emerging
at
trace concentrations (<0.1 mg/L). To assess the bioavailability
constraints on biodegradation, the roles of cell wall physiology and
transporters remain imperfectly understood. Here, compound-specific
isotope analysis (CSIA) demonstrates that cell wall physiology (i.e.,
the difference between Gram-negative and Gram-positive bacteria) imposes
mass transfer limitations in atrazine biodegradation even at high
concentrations. Atrazine biodegradation by Gram-negative Polaromonas sp. Nea-C caused significantly less isotope
fractionation (ε(C) = −3.5 ‰) than expected for
hydrolysis by the enzyme TrzN (ε(C) = −5.0 ‰)
and observed in Gram-positive Arthrobacter aurescens TC1 (ε(C) = −5.4 ‰). Isotope fractionation was
recovered in cell-free extracts (ε(C) = −5.3 ‰)
where no cell envelope restricted pollutant uptake. When active transport
was inhibited with cyanide, atrazine degradation rates remained constant
demonstrating that atrazine mass transfer across the cell envelope
does not depend on active transport but is a consequence of passive
cell wall permeation. Taken together, our results identify the cell
envelope of the Gram-negative bacterium Polaromonas
sp. Nea-C as a relevant barrier for atrazine biodegradation.
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Ehrl, Benno
N.; Gharasoo, Mehdi; Elsner, Martin (2018). Isotope
Fractionation Pinpoints Membrane Permeability
as a Barrier to Atrazine Biodegradation in Gram-negative Polaromonas sp. Nea‑C. ACS Publications. Collection. https://doi.org/10.1021/acs.est.7b06599
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AUTHORS (3)
BE
Benno
N. Ehrl
MG
Mehdi Gharasoo
ME
Martin Elsner
KEYWORDS
Gram-positive Arthrobacter aurescens TC 1Gram-negative bacterium Polaromonas spcompound-specific isotope analysisCSIAlimit atrazine degradationIsotope Fractionation Pinpoints Membrane Permeabilitycell envelopeatrazine mass transferGram-negative Polaromonas spatrazine biodegradationconcentrationatrazine degradation ratescell wall permeationmass transfer limitationscell wall physiology