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Fipronil is a highly active, broad spectrum insecticide with increasing and wide use. The degradation of fipronil was studied in Brazilian soil under oxic and anoxic conditions. Under oxic conditions, the half-life of fipronil was 16.9 days, with fipronil sulfone as the main metabolite, and no further degradation during 30 days of incubation. This degradation was accompanied by an increase of bacterial and archaeal ammonia oxidizers, as well as denitrifiers, and microorganisms related to Sphingomonas. Under anoxic conditions, a half-life of 15.7 days for fipronil was obtained, with fipronil sulphide as the primary metabolite, and fipronil sulfone at lower concentrations, with no further degradation of these metabolites during 90 days of incubation. In these conditions, complete degradation of fipronil was accompanied by an increase of denitrifiers, iron-reducers and ammonia oxidizers and selection of microorganisms that are related to uncultured Clostridiales (family VIII). Sulphate reducers and methanogens and most of the microbial community were not affected by fipronil and its metabolites. Toxicity evaluation, using in vitro effect-based CALUX assays confirmed that the metabolites have a similar toxic potency as compared to the parent compound fipronil. Therefore, the potential (eco)toxicity of fipronil does not seem to decrease upon microbial degradation.

Marine viruses are key drivers of host diversity, population dynamics and biogeochemical cycling and contribute to the daily flux of billions of tons of organic matter. Despite recent advancements in metagenomics, much of their biodiversity remains uncharacterized. Here we report a data set of 27,346 marine virome contigs that includes 44 complete genomes. These outnumber all currently known phage genomes in marine habitats and include members of previously uncharacterized lineages. We designed a new method for host prediction based on co-occurrence associations that reveals these viruses infect dominant members of the marine microbiome such as Prochlorococcus and Pelagibacter. A negative association between host abundance and the virus-to-host ratio supports the recently proposed Piggyback-the-Winner model of reduced phage lysis at higher host densities. An analysis of the abundance patterns of viruses throughout the oceans revealed how marine viral communities adapt to various seasonal, temperature and photic regimes according to targeted hosts and the diversity of auxiliary metabolic genes.