The AHL biosensor strain Agrobacterium tumefaciens NTL4[pZLR4] was grown in U0126 in vitro LB medium containing 30 μg mL−1 gentamicin (Luo et al., 2003). The method of Gantotti & Beer (1982) was used to generate a nonpigmented variant of P. vagans C9-1. An LB culture of C9-1 wild type was incubated at 38 °C for 24 h, and 10−5–10−6 dilutions were plated onto LB agar and incubated at 37 °C for 5 days. The nonpigmented variant C9-1W that was obtained was tested for the presence of the three C9-1 plasmids using PCR. Oligonucleotides (Supporting Information, Table S2)

were synthesized by Sigma-Genosys (Steinheim, Germany). The HotStarTaq Master Mix kit (Qiagen, Hilden, Germany) was used as described by the supplier. Chromosomal DNA was isolated using the Wizard Genomic DNA Purification Kit (Promega, Madison, WI). PCR was performed as described elsewhere (Innis et al., 1990). PCR products were visualized on 1.5% agarose gels (Sambrook et al., 1989). The metabolic profiles of P. vagans C9-1 and C9-1W were obtained using Biolog GN2 and AN plates (Hayward, CA). Precultures were grown in M9 medium with 5 mM glucose and allowed to grow to the late stationary phase to ensure complete substrate utilization. Cultures

were centrifuged at 4000 g and the cell pellets were washed once before resuspending in a fresh M9 medium. The attenuance at 600 nm (A600 nm) was set to 0.15 and each microtiter plate well was inoculated with 100 μL of this bacterial suspension. The plates were scored after 1, 2 and 5 days of incubation at 28 °C. For AHL bioassays, cell-free filtrates (150 μL) from see more stationary-phase cultures of P. vagans (16 h, 28 °C) were combined with 150 μL of a washed stationary-phase culture of A. tumefaciens NTL4[pZLR4] (Luo et al., 2003) (16 h, 28 °C) in a fresh LB medium containing 0.1% 5-bromo-4-chloro-3-indolyl β-galactoside (X-Gal). The production of AHL was determined qualitatively by observing a change to blue in the color of the microculture over the course of 3 days. The genome sequence

of plasmid pPag3 medroxyprogesterone from P. vagans C9-1 (Smits et al., 2009) was annotated using GenDB (Meyer et al., 2003) and was deposited at GenBank (Accession number CP001895). Sequence manipulations were performed using the Lasergene package (DNASTAR, Madison, WI). Additional blast searches (Altschul et al., 1990) were performed at NCBI (http://blast.ncbi.nlm.nih.gov/Blast.cgi). The genome sequence of P. vagans C9-1 (Smits et al., 2009) revealed a 530-kb plasmid, designated pPag3, encoding the carotenoid biosynthesis cluster crtEXYIBZ (Pvag_pPag30170–Pvag_pPag30175) as the most prominent feature. The encoded proteins share 91–97% sequence identity to the respective proteins of P. agglomerans pv. milletiae Wist 801 (GenBank: AB076662) and 70–89% to those of P. ananatis 20D3T (Misawa et al., 1990). The plasmid also carries four thiamine biosynthesis genes (thiOSGF; Pvag_pPag30158–Pvag_pPag30161) and a complete maltose metabolism gene cluster (Pvag_pPag30206–Pvag_pPag30215).