riparius endosymbionts (target organism) were obtained from homogenized internal genitalia of

female P. riparius. Probe specificities were evaluated with such cell suspensions of the Pseudomonas-like endosymbiont and the closely related P. aeruginosa (nontarget organism). A minimum of 300 DAPI-positive cells of randomly chosen areas on microscopic slides were evaluated. Scanning electron microscopy (SEM) studies of P. riparius eggs were carried out with a Philips FEI XL 30 ESEM. Subsequent to dehydration in ethanol (10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 30 min each), specimens were coated with gold (Edwards S150B). DNA was extracted using Qiagen DNA extraction kits (Qiagen, Hilden, Germany) according to the manufacturer’s protocol. A 157-base pair fragment of pks-gene encoding a ketosynthase involved in pederin biosynthesis was amplified with primers KS1F (5′-TGGCATCGT GGGGAAAGGCTG-3′) and KS1R (5′-GGCGCAGGTGCTGACACGC-3′) ITF2357 in vitro (pks-PCR; Piel, 2002). Primers were purchased from MWG-Eurofins (Ebersberg, Germany). PCR was performed in a total volume of 50 μL containing 24.8 μL PCR-H2O, 10.0 μL 5 × Q-Solution, 5.0 μL 10 × PCR buffer, 5.0 μL ddNTP Mix (2 mM), 2.5 μL of each primer (10 pmol μL−1), 0.2 μL Taq (5 U) (Qiagen). Thermal cycling was at 96 °C for buy FK506 5 min followed by 35 cycles of denaturation at 96 °C for 30 s, annealing at 57 °C for 30 s and extension at 72 °C for 1 min. Several potential

target sequences

for 16S rRNA gene-directed oligonucleotide probes were identified on the 16S rRNA gene sequence of the Pseudomonas-like bacterial endosymbiont of P. riparius (accession number: AJ316018; Kellner, 2002a). On the basis of different probe Carnitine palmitoyltransferase II parameters (e.g. length of probe, hybridization temperature, GC content, Escherichia. coli position, etc.), the probe with target site 444–461 (E. coli numbering according to Brosius et al., 1981) was selected (Table 1) and checked with the probe match-tool (the arb project: http://www.arb-home.de) for specificity. The probe (PAE444) was complementary to the target sequence of the Paederus endosymbiont and displayed high probe accessibility within its target region according to a 16S rRNA gene secondary structure model of E. coli (Fuchs et al., 1998; Behrens et al., 2003). PAE444 exhibited only two mismatches to the closest related nontarget sequence (P. aeruginosa). Thus, a competitor (cPAE444) complementary to the P. aeruginosa sequence was designed in order to achieve full mismatch discrimination (Table 1; Manz et al., 1992). PAE444 coverage alone was experimentally analysed by whole cell hybridization with cell suspensions of endosymbionts (extracted from P. riparius tissue, see Materials and methods) and pure cultures of P. aeruginosa. Probe dissociation curves were recorded to determine stringent hybridization and washing conditions. The nonhybridizing probe NON338 (Manz et al.