Isolation and characterization of metaldehyde-degrading bacteria from domestic soils

Metaldehyde is a common molluscicide, used to control slugs in agriculture and horticulture. It is resistant to breakdown by current water treatment processes, and its accumulation in drinking water sources leads to regular regulatory failures in drinking water quality. To address this problem, we isolated metaldehyde-degrading microbes from domestic soils. Two distinct bacterial isolates were cultured, that were able to grow prototrophically using metaldehyde as sole carbon and energy source. One isolate belonged to the genus Acinetobacter (strain designation E1) and the other isolate belonged to the genus Variovorax (strain designation E3). Acinetobacter E1 was able to degrade metaldehyde to a residual concentration < 1 nM, whereas closely related Acinetobacter strains were completely unable to degrade metaldehyde. Variovorax E3 grew and degraded metaldehyde more slowly than Acinetobacter E1, and residual metaldehyde remained at the end of growth of the Variovorax E3 strain. Biological degradation of metaldehyde using these bacterial strains or approaches that allow in situ amplification of metaldehyde-degrading bacteria may represent a way forward for dealing with metaldehyde contamination in soils and water.