Using seedlings inoculated with wild type Pseudomonas sp., DAPI staining and bright field microscopy were used to visualise the relationship between plant and bacteria. This revealed a biofilm was present on the surface of the root however it was unclear if the bacteria was inside the root, so seedlings were washed in distilled water. Examination of the cleaned seedlings revealed clear signs of colonisation and Pseudomonas sp. was present in intercellular spaces along both the root and hypocotyl. The bacteria were still motile and we could see them moving in real time.

Figure 14. Bright field microscopy of a DAPI stained Arabidopsis thaliana root at 40x magnification. Wild type Pseudomonas sp. is visible in the intercellular spaces.

A selection of Pseudomonas sp. transformant-inoculated seedlings were taken for microscopy, again seedlings were washed and DAPI stained.Endophytic bacteria were visible inside the root and hypocotyl of both Arabidopsis thaliana and Eruca sativa seedlings showing that transformation had not altered the bacteria’s ability to colonise.

Figure 21. Bright field microscopy of an Arabidopsis thaliana seedling root at x100 magnification,showing transformed Pseudomonas sp. living as an endophyte in the intercellular spaces.