The β-triketone herbicides are maize selective herbicides that have been largely applied in replacement of atrazine, banned in Europe in 2003. Their mode of action lays on the inhibition of the p-hydroxyphenylpyruvate dioxygenase (HPPD), a key enzyme of the carotenoid biosynthesis. In recent studies, we showed that within the soil bacterial community, many microorganisms possess a functional HPPD enzyme involved in tyrosine metabolism. These “non-target organisms” harbor the target of the β-triketone herbicides and consequently may be affected in response to its exposure. Within this context, the objective of our work is to check for the interest of hppd bacterial community as a marker of exposition and/or of impact sensitive to β-triketone herbicides. This will require the development of a molecular tool box to assess the abundance, activity and diversity of the hppd bacterial community in various arable soils exposed to β-triketone herbicides. The abundance and the activity of the hppd bacterial community will be monitored from the nucleic acids extracted directly from soils, and the diversity of the hppd community will be evaluated by a metagenomic study based on the high-throughput se- quencing of hppd amplicons. Our results will lead to the selection of a set of characteristic hppd sequences, allowing the development of hppd DNA chips to assess the ecotoxicological impact of β-triketone herbicides on soil microorganisms.