For crop plants that need sulfur (S) for the synthesis of proteins, the most important form of S is inorganic sulfates. However, inorganic sulfates represented only 5% of total S in soil and, as a result, symptoms of deficiency are frequently encountered in plants. Micro-organisms require S for growth and obtain it mainly as inorganic forms or alternatively from organic S compounds such as sulfonates and sulfate esters. Anyway, this common interest for acquisition of inorganic S for both, plants and micro-organism, leads to a strong competition notably in the rhizosphere. Arylsulfatase (ARS) is an important soil enzyme catalysing the hydrolysis of sulfate esters (ie the major labile form of organic S in soil) to generate sulfates. This microbial activity was already characterised in different bacterial genera. This work, aiming to the development of molecular tools targeting ARS, was conducted in the following way, (i) definition of primers from multiple alignments on arylsulfatase gene characterized in different bacteria, (ii) primer validation bacteria isolated from rhizosphere and possessing arylsulfatase activity, (iii) utilization of the primer to target bacterial community by metagenomic approach. The data yet available provide us the basis to develop molecular tools. Sequence alignments of various ats A genes available in gene banks (Pseudomonas aeruginosa PAO1, Klebsiella sp., Mycobacter sp.) were used to design degenerated PCR primers directed against ats A consensus domains. These primers which have been tested on various rhizosphere isolates belonging to different genera such as Pseudomonas, Ochrobactrum., Nocardia, Rhodococcus, Sinorhizobium, Cellulomonas., generated a PCR fragment which appeared to be affiliate to sulfatase of Pseudomonas fluorescens, arylsulfatase of Rhodococcus RHA1 or sulfatase of Mycobacterium. Finally, these degenerated PCR primers will be used in a metagenomic approach in soil to provide data about the density and the diversity the bacterial functional community and to investigate the role of this functional community in the plant S nutrition.