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Appl. Environ. Microbiol., Mar 1995, 1054-1060, Vol 61, No. 3
RM Zablotowicz, RE Hoagland, MA Locke and WJ Hickey
Glutathione-S-transferase (GST) activity was determined in 36 species of
rhizosphere bacteria with the substrate 1-chloro-2,4-dinitrobenzene (CDNB)
and in 18 strains with the herbicide alachlor. Highest levels of CDNB-GST
activity (60 to 222 nmol (middot) h(sup-1) (middot) mg(sup-1)) were found
in gram-negative bacteria: Enterobacter cloacae, Citrobacter diversus,
Klebsiella planticola, Pseudomonas cepacia, Pseudomonas fluorescens,
Pseudomonas putida, and Xanthomonas campestris. There was very low CDNB-GST
activity in the gram-positive strains. Rapid metabolism of CDNB-glutathione
conjugates, attributable to high levels of (gamma)-glutamyltranspeptidase,
also occurred in the gram-negative bacteria, especially pseudomonads.
Alachlor-GST activity detected in cell extracts and whole-cell suspensions
of some strains of the families Enterobacteriaceae and Pseudomonaceae was
50- to 100-fold lower than CDNB-GST activity (0.5 to 2.5 nmol (middot)
h(sup-1) (middot) mg(sup-1)) and was, for the most part, constitutive. The
glutathione-alachlor conjugate was rarely detected. Cysteineglycine and/or
cysteine conjugates were the major products of alachlor-GST metabolism.
Whole-cell suspensions of certain Pseudomonas spp. dechlorinated from 20 to
75% of 100 (mu)M alachlor in 24 h. Results indicate that rhizosphere
bacteria, especially fluorescent pseudomonads, may play an important role
in the degradation of xenobiotics such as alachlor via GST-mediated
reactions.
Copyright © 1995, American Society for Microbiology
Glutathione-S-Transferase Activity and Metabolism of Glutathione Conjugates by Rhizosphere Bacteria
USDA-ARS Southern Weed Science Laboratory, Stoneville, Mississippi 38776, and Soil Science Department, University of Wisconsin, Madison, Wisconsin 53706
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