, 2004). Monoterpenes and related compounds can have diverse effects in mammalians (see Ishida, 2005; Paduch et al., 2007; Bakkali et al., 2008). Considerable literature is available on biotransformation reactions with terpenoid compounds

(reviewed in van der Werf et al., 1997; Duetz et al., 2003; de Carvallo & da Fonseca, 2006), but knowledge on the catabolic pathways of terpenoids in organisms is poor. Acyclic terpenes can be used as a single source of carbon and energy only by Pseudomonas citronellolis (Seubert, 1960) and a few related species such as Pseudomonas aeruginosa, Pseudomonas mendocina (Cantwell et al., 1978), Pseudomonas delhiensis (Prakash et al., 2007) and some strains of Pseudomonas fluorescens and of Pseudomonas putida (Vandenbergh & Wright, 1983; Vandenbergh & Cole, 1986). Selleckchem Everolimus The catabolic pathway of acyclic monoterpenes proceeds via the acyclic terpene utilization (Atu) pathway, which was first described by Seubert and colleagues half a century ago (Seubert & Remberger, 1963; Seubert et al., 1963; Seubert & Fass, 1964a, b) (overview in Supporting Information, Fig. S1). Recently, we identified the atu gene clusters (atuABCDEFGH) of P. aeruginosa (Höschle et al., 2005; Förster-Fromme et al., 2006) and a highly similar cluster of P. citronellolis (Förster-Fromme & Jendrossek,

2006) that are essential for citronellol Galunisertib cell line catabolism in both species and that code for most proteins of the Atu pathway. Some selected genes and proteins of the Atu pathway and of the downstream leucine/isovalerate utilization pathway have been identified and characterized recently (Höschle et al., 2005; Aguilar et al., 2006, 2008; Förster-Fromme et al., 2006; Chavez-Aviles et al., 2009). Expression of Atu proteins is regulated and requires the presence of acyclic terpenes as inducer compounds. A putative transcriptional regulator gene (atuR) is located 280 bp upstream of and in an orientation opposite to the atuABCDEFGGH gene cluster. In this contribution, we investigated the function of atuR by

mutant analysis and identified the DNA-binding sites of purified AtuR by an electrophoretic mobility shift assay (EMSA). All experiments were performed with P. aeruginosa PAO1 or with Escherichia coli. Cultures of P. aeruginosa PAO1 were routinely grown in Luria–Bertani (LB) media or in a mineral salt medium containing different carbon out sources (0.1% v/v sodium citronellate, 0.1% v/v sodium geranylate and 0.1% v/v sodium isovalerate) at 30 °C. For details, see Förster-Fromme et al. (2006). Liquid cultures contained 0.5% w/v glucose or 0.1% w/v glucose and 0.2% w/v of sodium citronellate, 0.2% sodium isovalerate (w/v), 0.1% sodium octanoate (v/v) or 0.1% 1-octanol (v/v), respectively. Escherichia coli strains were grown in LB media at 37 °C. Isolation of chromosomal DNA of P. aeruginosa and other molecular biological methods were performed using standard procedures. The primers used for PCR reactions are summarized in Table 1.