Cucumber (Cucumis sativus L.) seeds of the cultivar JinChun 5 were surface-sterilized in 2% NaClO for 3 min and 75% ethanol for 2 min and then rinsed 3 times in sterile water. The seeds were then germinated on 9-cm plates covered with sterile wet filter paper at 25 °C for 48 h. GFP-tagged N43 cells were grown in Luria Bertani (LB) medium containing 20 μg ml−1 of kanamycin for 24 h. The bacteria were harvested by centrifuging at 5000 × g for 10 min and washing twice with phosphate-buffered saline (PBS) with a pH 7.0. The soil used in the experiment was inoculated with the bacterial suspension to obtain final concentrations of 105, 106, 107 and 108 cells per g of soil. After inoculation, germinated seeds were transferred to the soil, irrigated with 1/2 Hoagland medium and incubated in a growth chamber at 25 °C under a 16-h light regimen.