THE SIGNIFICANCE OF NON-HERITABLE STRESS TOLERANCE IN THE MODEL PLANT PATHOGEN PSEUDOMONAS SYRINGAE

Controlling microbial plant pests is important to the economic and food security of both the US and global human population. Past efforts to improve microbial control have focused primarily on optimizing inhibition of microbial pests that are highly sensitive to a given control mechanism, such as an antibiotic. Microbes in nature, including those that cause plant diseases, likely exist in varying 'dormant' states that make them tolerant to a control mechanisms, as well as allowing them to persist in fields over multiple years to cause recurrent disease. Such 'dormant' states are a major factor in post-antibiotic recurrence of human infection, and are thought to play a major role in the ecology of plant disease. The cost of 'dormant' states is primarily a problem for growers, who suffer economic losses from lost yields due to plant disease and higher production costs associated with needing to spray greater amounts of chemical or biological control agents. This cost is further passed on to consumers in the form of higher prices. Additionally, the public at large suffers from microbial 'dormancy' because additional application of antibiotics or related chemicals results in greater environmental exposure to these chemicals, as well as a reduced ability to access affordable organic produce.To better understand microbially stress tolerance, we will focus on determining specifically how microbes tolerate stress at multiple levels. We will a) identify the genes that contribute to stress tolerance, b) determine at the cellular level what is different about a cell that can tolerate a given stress and one that can not, and c) test how well cells that are either able or unable to tolerate stresses can survive and proliferate within a plant environment. This project will result in a new understanding of the prevalence and significance of lethal stress tolerance in bacterial plant pathogens, an area of study that is both critically important but currently underappreciated. In addition, it will identify how this stress tolerance is achieved, which could lead to strategies to predict and manipulate the ability of both detrimental and beneficial microbes to survive in agricultural environments.