Niche construction by plant pathogenic pseudomonads

Plant pathogens such as the bacterial pathogen Pseudomonas syringae infect plant tissues by injecting secreted proteins into plant cells to suppress plant defences, and by producing toxins and hormones that alter plant physiology to promote bacterial growth. The ability of P. syringae to manipulate its plant hosts can be regarded as a form of niche construction or ecosystem engineering, processes in which the activities of an organism or group of organisms alter the environment occupied by their descendants and by other organisms within the same ecosystem.
We have shown that the presence of P. syringae in plant tissues alters the chemical composition of the apoplastic fluid that surrounds plant cells, in which P. syringae grows. These changes may promote or restrict P. syringae virulence and growth, as well as altering plant fitness and interactions with other organisms. The aim of this project will be to investigate whether the chemical changes we have observed in the apoplast of infected plants represent positive or negative niche construction, i.e. whether they promote or inhibit the growth of subsequent generations of bacteria. We will also consider whether niche construction on an evolutionary time-scale has shaped the metabolic and regulatory features of P. syringae. In the long term we hope to use knowledge of niche construction by plant pathogens to develop novel strategies to enhance disease control.