Spectroscopic methods OD (660 nm) and PM levels (880 nm) were measured using a 1 cm path length cuvette and a UV/Vis spectrophotometer (V-560, Jasco, Tokyo, Japan). The PM level was estimated using the A880/A660 ratio. An A880/A660 ratio of approximately 1.2 is characteristic of maximal PM levels, obtained in anaerobic phototrophic cells grown at low levels of light intensity. An A880/A660 ratio of approximately 0.54 is indicative of a lack of PM formation, see more and occurs in aerobic cultivation conditions [4]. ΔPM refers to the amount of PM produced during a

specific growth period. Culture supernatants were analyzed for levels of bacteriochlorophyll a precursors by fluorescence spectroscopy using a Varian fluorescence spectrophotometer of the type Cary Eclipse (Cary Eclipse, Varian, Palo Alto, CA). Tetrapyrolle compounds produced in growth cultures were identified LY2606368 in vitro as described previously [11]. For quantification of both compounds, the emission spectra of culture supernatants were evaluated at their maximum emission (FImax). Protoporphyrin-IX (PPIX) showed a FImax at 614 nm when excited at 390 nm, whereas magnesium-protoporphyrine-IX-monomethylesther (Mg-PPIX-mme) showed a FImax at 595 nm when excited at 420 nm. Purification and quantification of AHL extracts

Culture supernatants were extracted with dichloromethane in a ratio of 7:3 (v/v). After evaporation of the solvent, the dried AHL residue was learn more resuspended in C59 purchase 100% (v/v) acetonitrile (ACN) at 1/100 of the origin volume. In preparation for analytical high performance liquid chromatography (HPLC) analysis, the samples were filtered (0.2 μm, GHP, Minispike Acrodisc® Syringe Filters, Pall Life Sciences, New York, USA) to remove particulate matter. The samples were processed on a HPLC from Agilent (1100 series, Agilent, Waldbronn, Germany) consisting of quaternary pump, autosampler, DAD-detector and the matching LC/MSD detector or a 1200 series sample collector. The LC/MSD (1100 series, Agilent, Waldbronn, Germany) was used with either an APCI-ion source or ESI. The Inertsil ODS-3 column was 4.6 x 250 mm, with a 5 μ particle size (Inertsil 100A ODS-3, VDS

Optilab, Berlin, Germany). The eluent gradient was from ACN:H2O; (10:90; v/v) to ACN:H2O (90:10; v/v) over 15 min. For restoring the original concentrations between samples, a 5 min flow interval, followed by 3 additional minutes for equilibration was used. For sensitive analysis, the flow rate was 1 mL min-1. For semi-preparative applications involving a larger column (10 x 250 mm), the flow rate was adjusted to 3 mL min-1. Screen for AHL bioactivity Autoinducer bioassays [18] were performed employing A. tumefaciens NTL4 (pZLR4) as indicator strain. The overlay culture was prepared as described previously [19]. An appropriate amount of AHL extracts was spotted on glass microfibre filters (90 mm Ø, Cat No 1822–090, Whatman, GE Healthcare UK limited, Little Chalfont, UK) which were then placed into a Petri dish.