Briefly, 100 μl overnight cultures of bacteria strains and isolates (LB with appropriate antibiotics) were mixed, in 1:1:1 proportion (SM17, SM10, and LCN-16 or PWN-146), pipetted onto a 13-mm cellulose acetate filter membrane and placed on non-selective LB medium. Plates were incubated overnight at 28°C. In the following day, filters were placed into a sterile microcentrifuge tube containing Alisertib 0.2 ml of 0.9% NaCl and vortexed for cell suspension. Aliquots of 100 μl of each suspension was plated onto LB with selective antibiotic (30 μg/ml gentamycin) and overnight incubated at 28°C. Bacteria association to nematode Bacteria isolates (LCN-4, LCN-16 and PWN-146)

and strain (OP50) were grown overnight in LB broth at 28°C or 37°C, pelleted at 10,000 rpm for 5 min, washed twice with sterilized DW, and adjusted OD600 for 1.00 (± 107-108 CFU/ml). Two approaches were used to associate bacteria with B. xylophilus. The first

approach consisted in the observation of 1 h contact bacterial association with B. xylophilus, before and after washing nematodes for the oxidative stress tests. Firstly, nematodes were surface sterilized and the concentration adjusted to 150 nematodes per 50 μl of sterilized DW. Nematode-bacteria association was performed by 1 h contact between surface cleaned nematodes and 1 ml of bacterial suspension (concentrations were adjusted as described above) and in accordance to Han et al. [50] procedure. Afterwards, bacteria suspension was removed by pelleting the nematodes CHIR-99021 chemical structure at low high throughput screening speed rotation (800 × g, 5 min), and then hand-picked with a nematode picker (steel wire) and transferred into a drop of sodium azide (1 M) on the centre of the agar pad [51], covered and sealed with a silicon grease-rimmed coverslip for viewing by Nomarski DIC optics. The second approach consisted in co-culturing of B. xylophilus Ka4 with GFP-tagged bacteria (LCN-16-GFP;

PWN-146-GFP) in 0.1% MEA plate seeded with B. cinerea. Firstly, nematodes were cultured on the 0.1% MEA plate for three-days, and then 500 μl of bacterial suspension (concentrations were adjusted as described above) were added and co-cultured for 24 h at 28°C. Afterwards nematodes were extracted, washed and mounted on the agar pad as described above. GFP-tagged bacteria were observed with a ZEISS Axiovert 200 microscope equipped with a confocal laser-scanning module. Oxidative stress tolerance tests To test bacteria tolerance to the oxidative agent, 100 μl of freshly prepared H2O2 and 10 μl of bacteria (concentrations were adjusted as described above) were placed into each well of a 96-well plate and at a total volume of 110 μl per well. Final concentrations of H2O2 were 0, 15, 20, 30 and 40 mM. After 24 h, the plates were read in a multi-spectrophotometer (Viento, Dainippon Sumitomo Pharma, Japan) at OD600. For each B. xylophilus associated bacteria and control E. coli.