Hyper-thermostable enzyme (Lactonases) for use as microbial biocontrol agents for plant diseases.

University of Minnesota/Mike Sadowsky

Many bacterial pathogens infect crop plants, representing major economic burdens. This also limits our ability to feed the world’s populations. Current methods for controlling plant diseases due to bacterial infection have had limited success, in part due to bacterial resistance and specificity. Novel strategies are therefore greatly needed to control microbes. Numerous bacterial pathogens use chemical signaling systems to coordinate virulence factor expression and biofilm formation. A common bacterial communication mechanism called quorum sensing (QS) regulates bacterial gene expression in response to fluctuations in cell density. A common class of QS molecules are acyl homoserine lactones (AHLs). The hydrolysis of AHLs lead to the disruption of bacterial communication, and a subsequent reduction of virulence and biofilm formation. The use of a controlled biologically-derived agent, e.g. a lactonase preparation, to control plant pathogens, is therefore appealing. Our group has isolated and engineered enzymes that are highly proficient and extremely stable, that can be used as biocontrol agents and be active at all times, independently of the ecosystem. Over the last year, we have demonstrated that this approach can protect a variety of plants, including corn, from infection. Our results were exciting as we learned that crop protection is broad, extending from grasses (Corn, Wheat, and Barley) to Dicots (Soybean, Field Beans, and Potato). Over the last year we have: 1) established growth chamber methods to effectively grow and infect corn, and a variety of other plants, 2) developed and evaluated plant infection/protection assays, and 3) tested efficacy of the lactonases to control disease and at the same time examined their influence on leaf microbiota. Here we propose to improve formulation of this enzyme, examine its ability to reduce pre- and post-harvest damage to crops during storage, and examine how the enzyme can function against atypical bacteria.