A rapid method to screen degradation ability in chlorophenoxyalkanoic acidherbicide-degrading bacteria

Aims: An agar medium containing a range of related chlorophenoxyalkanoic ac id herbicides, 2,1-dichlorophenoxyacetic acid (2,4-D), 2-methyl-4-chlorophe noxyacetic acid (MCPA), racemic mecoprop, (R)-mecoprop and racemic 2,4-DP ( 2-(2,-4-dichlorophenoxy) propionic acid) was developed to assess the catabo lic activity of a range of degradative strains. Methods and Results: The medium was previously developed containing 2,4-D a s a carbon source to visualise degradation by the production of dark violet bacterial colonies. Strains isolated on mecoprop were able to degrade 2,4- D, MCPA, racemic mecoprop, (R)-mecoprop and racemic 2,4-DP, whereas the 2,4 -D-enriched strains were limited to 2, 4-D and MCPA as carbon sources. Sphi ngomonas sp. TFD44 solely degraded the dichlorinated compounds, 2,4-D, race mic 2,4-DP and 2,4-DB (2,4-dichlorophenoxybutyric acid). However, Sphingomo nas sp. AW5, originally isolated on 2,4,5-T, was the only strain to degrade the phenoxybutyric compound MCPB (4-chloro-2-methylphenoxybutyric acid). Conclusions: This medium has proved to be a very effective and rapid method for screening herbicide degradation by bacterial strains. Significance and Impact of the Study: This method reduces the problem of as sessing the biodegradability of this family of compounds to an achievable l evel.