Dynamics of multigene expression during catabolic adaptation of Ralstonia eutropha JMP134 (pJP4) to the herbicide 2,4‐dichlorophenoxyacetate

Abstract

Ralstonia eutropha JMP134 carries a 22 kb DNA region on plasmid pJP4 necessary for the degradation of 2,4-D (2,4-dichlorophenoxyacetate). In this study, expression of the 2,4-D pathway genes (designated tfd ) upon exposure to different concentrations of 2,4-D was measured at a detailed timescale in chemostat-grown R. eutropha cultures. A sharp increase in mRNA levels for tfdA, tfdCDEF-B, tfdDIICIIEIIFII-BII and tfdK was detected between 2 and 13 min after exposure to 2,4-D. This response time was not dependent on the 2,4-D concentration. The genes tfdA, tfdCD and tfdDIICII were expressed immediately upon induction, whereas tfdB, tfdBII and tfdK mRNAs could be detected only around 10 min later. The number of tfd mRNA transcripts per cell was estimated to be around 200-500 during maximal expression, after which they decreased to between 1 and 30 depending on the 2,4-D concentration used for induction. Unlike the mRNAs, the specific activity of the 2,4-D pathway enzyme chlorocatechol 1,2-dioxygenase did not increase sharply but accumulated to a steady-state plateau, which was dependent on the 2, 4-D concentration in the medium. At 1 mM 2,4-D, several oscillations in mRNA levels were observed before steady-state expression was reached, which was caused by transient accumulation of the first pathway intermediate, 2,4-dichlorophenol, to toxic concentrations. Expression of tfdR and tfdS, the (identical) regulatory genes for the tfd pathway remained low and essentially unchanged during the entire adaptation phase.

Transcriptional co-regulation of five chitinase genes scattered on the Streptomyces coelicolor A3(2) chromosome

“…Similar phenomena have been observed in various other systems (Baumann et al, 1996 ;Schwarts et al, 1998 ;Leveau et al, 1999 ;Iyer et al, 1999). For instance, in 2,4-dichlorophenoxyacetate (2,4-D)-utilizing Ralstonia eutropha JM134(pJP4), the 2,4-D-induced transcription from TfdR\S-regulated promoters decreased soon after the initial increase (Leveau et al, 1999). In this system, 2,4-dichloromuconate, a pathway intermediate in 2,4-D utilization, is the signal for TfdR\S-mediated expression.…”

“…In this system, 2,4-dichloromuconate, a pathway intermediate in 2,4-D utilization, is the signal for TfdR\S-mediated expression. It was assumed that the induction of intracellular enzymes that degrade the signal molecule caused the decrease in the tfd gene expression (Leveau et al, 1999). Although the signal molecule(s) for the induction of the chitinase genes in S. coelicolor A3(2) is still not identified, the other enzymes of the metabolic pathway for chitin or chitobiose utilization might degrade the signal molecule(s) or its precursor(s), resulting in the decrease of chitinase genes transcripts.…”

Identification and Growth Characterization of a Novel 2,4-D (Dichlorophenoxyacetic Acid) Degrading Bacterium Maribacter Sp Amsu Isolated From Aquaculture Effluent

“…Ingestion of high doses of 2,4-D have shown acute toxicity in lower mammals and humans and most of the strains have been well characterized (Fulthorpe et al, 1996). The catabolic pathway of 2,4-D mineralization by Ralstonia eutropha Jmp134 was investigated by Leveau et al (1999), Don and Pemberton (1981) and more recent studies have also elucidated the kinetics of 2,4-D degradation. The kinetics of cell growth and biodegradation of 2,4-D of microorganisms growing on herbicide was also reported by Muller et al (2001) and Fuchslin (2003).…”

Monitoring Key Reactions in Degradation of Chloroaromatics by In Situ 1 H Nuclear Magnetic Resonance: Solution Structures of Metabolites Formed from cis -Dienelactone

“…R. eutropha JMP222 is a derivative of R. eutropha JMP134 (9) cured of plasmid pJP4. pJP4 was shown to contain two chlorocatechol gene clusters, namely, module I (8) and module II (17), which both encode a "maleylacetate" reductase (15,28). Only module I was present in JMP222(pBBR1M-I).…”