Biotransformation of phenylarsenic chemical warfare agents and their effect on bacterial communities in the Baltic Sea sediment
Primary oxidation products of phenylarsenic chemical warfare agents (CWAs) have been detected in marine sediments collected near dumping sites. Recent studies showed the presence of other degradation products, possibly formed in microbial biotransformation. Here, we studied the role of microbes in the biotransformation of phenylarsenic CWAs, and how bacterial communities in marine sediments are affected by phenylarsenic CWAs. Baltic Sea sediments were spiked with phenylarsenic CWAs and incubated under seabed mimicking conditions. Samples were screened for known and new biotransformation products by ultrahigh-performance liquid chromatography high-resolution mass spectrometry. Bacterial community structure and diversity were investigated by 16S rDNA sequencing. Spiking of phenylarsenic CWAs affected the community structure. In particular, the amount of Arcobacteriaceae increased in anoxic Bornholm samples already within one week after spiking with phenylarsenicals. Several previously suspected and completely new phenylarsenic compounds were identified in the spiked sediments. These compounds are modifications of the spiked chemicals, with additions of sulphur or methyl, or both to the original structure. The results suggest that sulphur-containing phenylarsinic compounds are rapidly produced through chemical reactions with reactive sulphur present in the sediment, whereas methylation of the spiked chemicals is likely due to gradual metabolic conversion by microbiota.