Affiliation:
1. Agriculture and Agri-Food Canada, London, Ontario, Canada N5V 4T3,1 and
2. Soil Microbial Systems Laboratory, ARS/U.S. Department of Agriculture, Beltsville, Maryland 207052
Abstract
ABSTRACT
Atrazine, a herbicide widely used in corn production, is a frequently detected groundwater contaminant. Nine gram-positive bacterial strains able to use this herbicide as a sole source of nitrogen were isolated from four farms in central Canada. The strains were divided into two groups based on repetitive extragenic palindromic (rep)-PCR genomic fingerprinting with ERIC and BOXA1R primers. Based on 16S ribosomal DNA sequence analysis, both groups were identified as
Nocardioides
sp. strains. None of the isolates mineralized [
ring
-U-
14
C]atrazine. There was no hybridization to genomic DNA from these strains using
atzABC
cloned from
Pseudomonas
sp. strain ADP or
trzA
cloned from
Rhodococcus corallinus. S
-Triazine degradation was studied in detail in
Nocardioides
sp. strain C190. Oxygen was not required for atrazine degradation by whole cells or cell extracts. Based on high-pressure liquid chromatography and mass spectrometric analyses of products formed from atrazine in incubations of whole cells with H
2
18
O, sequential hydrolytic reactions converted atrazine to hydroxyatrazine and then to the end product
N
-ethylammelide. Isopropylamine, the putative product of the second hydrolytic reaction, supported growth as the sole carbon and nitrogen source. The triazine hydrolase from strain C190 was isolated and purified and found to have a
K
m
for atrazine of 25 μM and a
V
max
of 31 μmol/min/mg of protein. The subunit molecular mass of the protein was 52 kDa. Atrazine hydrolysis was not inhibited by 500 μM EDTA but was inhibited by 100 μM Mg, Cu, Co, or Zn. Whole cells and purified triazine hydrolase converted a range of chlorine or methylthio-substituted herbicides to the corresponding hydroxy derivatives. In summary, an atrazine-metabolizing
Nocardioides
sp. widely distributed in agricultural soils degrades a range of
s
-triazine herbicides by means of a novel
s
-triazine hydrolase.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
188 articles.
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