DEVELOPMENT AND EVALUATION OF BACTERIOCINS AS ROBUST BACTERIAL PHYTOPATHOGEN CONTROL COMPOUNDS

Crop loss resulting from microbial plant pathogens is a major obstacle in efficiently producing the food necessary to feed the world's growing population. Plant disease ultimately results in higher produce costs for consumers and reduced revenue for producers, thus resulting in negative economic impacts. Additionally, certain pathogens, such as Pseudomonas syringae, can evolve to cause particularly destructive disease, which can devestate a particular crop over large geographic regions. Examples of this include the recent outbreak of P. syringae in New Zealand that has severly affected kiwi production, a staple of New Zealand agriculture. Historical methods to control disease incited by P. syringae, as well as other bacterial plant pathogens, rely largely on chemical biocides which have several draw backs. First, many of these compounds have lost their effectiveness as a result of evolution of biocide resistance within the pathogen, thus rendering these chemical ineffecitve in controlling disease. Second, these compounds are broadly toxic, which results in undesireable environmental impact.Selectively toxic proteins produced by bacteria, termed bacteriocins, represent a potentially ideal alternative to controlling plant disease when compared to traditional chemical treatments. They are very specific in their toxicity, and thus are environmentally benign, and do not pose a risk to human health. Additionally, they have the potential to be easily modifiable, thus researchers will be able to quickly retool them to target novel pathogens as they arise. Before bacteriocins can be adopted for such uses, however, we must first answer some basic questions, which I aim to do through my research project. First, I will research the genetics behind the bacteriocins in P. syringae. Second, I will assess the effect of bacteriocin exposure on target pathogens. This will allow me to understand how a bacteriocin-based control strategy will likely affect pathogens (that is, how easily does bacteriocin resistance evolve? Do resistance mutations make the pathogen less able to cause disease crops?). Finally, I will test several methods of applying bacteriocins to plants to determine what is the best method for utilizing these compounds (i.e. which method will best prevent plant disease). The ultimate goal of this work is to develop a new method of controlling plant disease that is both more effective and reliable than current methods, as well as being more environmentally benign. This work will help ensure reliable, low cost agricultural goods for consumers in the US by lowering production costs for growers.