Palumbo and J. Martinis for their help in the experiments. We thank I. Gianicolo, A. Zambonelli, M. Iotti, A. Mello, B. Finot and A. de Miguel for providing fruiting bodies of Tuber species, and E. Martino for providing O. maius isolates. M.V. and C.M. acknowledge financial support by the University of Turin. E.Z. PhD fellowship was funded by the University of Turin. This research was funded by the University I-BET-762 concentration of Turin, by Fondazione Sanpaolo and by Regione Piemonte. C.M. and E.Z. contributed equally to this work. “
“Although the biosynthesis of oxalic acid is known to occur in a number of bacteria, the mechanism(s) regulating its production remains largely unknown. To date, there is no report on

the identification of an oxalic acid ZD1839 molecular weight biosynthetic pathway gene from bacteria. In an attempt to identify such a gene(s), a mutant screen was conducted using the simple oxalic acid-producing phytopathogenic bacterium, Burkholderia glumae. Four mutants that failed to produce oxalic acid were isolated from

a transposon-mutagenized B. glumae library and named Burkholderia oxalate defective (Bod)1. DNA sequence analysis revealed that each mutant contained an insertion event at different sites in the same ORF, which we referred to as the oxalate biosynthetic component (obc)A locus. Complementation of the Bod1 mutant with the obcA gene, however, resulted only in a partial restoration of the oxalic acid-producing phenotype. Further complementation studies utilizing a larger DNA fragment encompassing the obcA locus coupled with deletion mutagenesis led to the identification of another ORF that we named the obcB locus,

which was essential for higher levels of oxalic acid production. Transcript analysis indicated that both obcA and obcB are coexpressed and encoded on a single polycistron message. Oxalic acid is the simplest of the organic dicarboxylic acids. It is considered a relatively strong acid with good reductive power, making it prevalent in a variety of industrial applications (Strasser et al., 1994; Rymowicz & Lenart, 2003; Meyer-Pinson et al., 2004). Currently, the bulk of the acid is produced chemically, but there has been some interest in the development of fermentative processes utilizing oxalic acid-producing microorganisms (Strasser et al., 1994; Rymowicz & Lenart, 2003; Meyer-Pinson et al., 2004). As in the SPTLC1 chemical industry, oxalic acid is also common in nature; its biosynthesis has long been known to occur in a variety of organisms such as bacteria, fungi, plants, and animals (Hodgkinson, 1977; Franceschi & Nakata, 2005). The functional role of oxalate in each organism can differ along with its chemical form and distribution (Hodgkinson, 1977; Dutton & Evans, 1996; Franceschi & Nakata, 2005). In microorganisms, oxalic acid has been shown to serve a number of important functions, which include roles in metal tolerance (Dutton & Evans, 1996; Sayer & Gadd, 1997; Appanna & Hamel, 1999; Green & Clausen, 2003), nutrient acquisition (Shimada et al.