Pseudomonas putida KT2240 derives from a strain isolated in an orchard in Japan. It can efficiently colonize the roots and rhizosphere of different plants and exert a positive effect on plant growth, particularly under stress conditions. It also stimulates induced systemic resistance (ISR) of the plant against certain pathogens. The genetic basis for efficient root colonization, the transcriptional reprogramming of root-associated populations, and the mechanisms involved in plant protection and growth promotion are some of the aspects we have been studying over the years.
We have recently extended our interest to another beneficial root-colonizing bacterium: Pseudomonas stutzeri MJL19. This strain was isolated from an extremely saline environment and it has been shown to protect plants from salt stress. Interestingly, MJL19 has naturally high c-di-GMP levels, and forms dense biofilms on roots. The basis for salt tolerance and the regulation of second messenger levels in this bacterium are among our current research lines.
We have also started to investigate c-di-GMP turnover and biofilm development in the plant pathogen Xylella fastidiosa. This microorganism is an emerging menace in the Mediterranean area, as it can colonize the xylem of many different plants of agricultural relevance.