Phototrophic Microorganisms: A Potent Biodegrading Community Whose Contribution to Pesticide Fate is Currently Overlooked

Throughout the history of pesticide regulation, laboratory studies on microbial metabolism have been conducted in continuous darkness. This was based on a presumption that the communities responsible for pesticide degradation are predominantly bacteria and fungi. However, conducting studies in this way excludes the potential contribution of phototrophic microorganisms (algae) which will be present to some extent in all terrestrial and aquatic ecosystems. Despite a number of publications showing that algae can metabolise xenobiotic compounds in pure culture, there is little data on their potential to metabolise pesticides in more realistic test systems. Over recent years Syngenta have developed higher tier studies (both in soil and aquatic test systems), often simply based on introducing a suitable light-dark cycle into OECD regulatory studies, which capture the contribution of algae to the overall degradation of pesticides.