Degradation of 2,4-dichlorophenoxyacetic acid by haloalkaliphilic bacteria

Abstract

Three 2,4-dichlorophenoxyacetic acid (2,4-D)-degrading bacterial isolates were obtained from the highly saline and alkaline Alkali Lake site in southwestern Oregon contaminated with 2,4-D production wastes. While similar in most respects, the three isolates differed significantly in 2,4-D degradation rates, with the most active strain, 1-18, demonstrating an ability to degrade up to 3000 mg 2,4-D I-1 in 3 d. This strain was well adapted to the extreme environment from which it was isolated, growing optimally on 2,4-D at pH 8.4-9.4 and at sodium ion concentrations of 0.6-1.0 M. According to its optimum salt concentration and pH for growth, this isolate was a moderately halophilic, alkaliphilic bacterium. The 16S RNA gene sequence (303 nt) was identical for all three isolates and most closely resembled those of the moderately halophilic eubacteria of the family Halomonadaceae (91% identity). Biochemical and genetic examination revealed strain 1-18 utilizes the same 2,4-D degradation pathway as most of the 2,4-D-degrading bacteria from non-extreme environments. Hybridization data and comparison of the partial sequences of the tfdA gene from the Alkali Lake isolates with those of bacteria from non-extreme environments suggested a common genetic origin of the 2,4-D degradation pathway in the two groups of micro-organisms.

Uptake Kinetics of 2,4-Dichlorophenoxyacetate byDelftia acidovoransMC1 and Derivative Strains: Complex Characteristics in Response to pH and Growth Substrate

“…The tfdA gene is widely distributed in a range of bacterial strains that belong to the and subdivisions of Proteobacteria. [4][5][6][7][8][9][10][11][12] Strains selected for their capability to utilize racemic phenoxypropionate herbicides like (RS)-2-(2,4-dichlorophenoxy)propionate (2,4-DP, dichlorprop) and (RS)-2-(4-chloro-2-methylphenoxy)propionate (MCPP, mecoprop) are more rare. Examples are Sphingobium herbicidovorans MH, 8,[13][14][15] Delftia acidovorans MC1, 16,17) Rhodoferax sp.…”

Halomonas organivorans sp. nov., a moderate halophile able to degrade aromatic compounds

“…On the other hand, the genus Halomonas is a taxon comprising strains that are metabolically versatile: some Halomonas species have been described as denitrifying halophilic bacteria useful in the reduction of nitrate during the treatment of saline waste (Berendes et al, 1996;Mormile et al, 1999;Romano et al, 1996;Dobson & Franzmann, 1996). In addition, there are also a few reports on Halomonas strains able to degrade aromatic pollutants (Maltseva et al, 1996;Muñoz et al, 2001). …”

Root Nodule Bradyrhizobium spp. Harbor tfdA α and cadA , Homologous with Genes Encoding 2,4-Dichlorophenoxyacetic Acid-Degrading Proteins

“…2,4-dichlorophenoxyacetic acid (2,4-D) has been used as a herbicide since the 1940s, and a number of its degrading bacteria have been isolated worldwide from a variety of environments and extensively examined on a molecular basis (1,2,4,17,20,24,27,34,38,39,41). The most extensive studies have been done with Ralstonia eutrophus JMP134, which carries a 2,4-D-degrading gene cluster on the transmissible plasmid pJP4 (4,24,32).…”