Molecular mechanisms involved in pseudomonas biocontrol

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Modern day crop protection relies heavily on the use of chemical pesticides. Increasing public concern over the risk these chemicals pose to the environment and human health has led to a search for a safer alternatives. Some bacteria naturally present in soil are able to inhibit the ability of fungi to cause disease in plants. As these bacteria do not cause disease in humans or other animals, they are an environmentally friendly alternative to chemical pesticides. Sclerotinia sclerotiorum is a fungus that causes devastating losses in canola as well as over 400 other crop species. Two bacteria have been isolated from the environment, Pseudomonas chlororaphis strain PA23 and Pseudomonas sp. DF41 that are able to control the growth of this fungus and protect canola from disease. Unfortunately in the past, commercial use of bacteria to manage crop diseases has met with limited success. This is most likely due to fluctuations in environmental conditions, which cause variations in the amount of antifungal products produced by the beneficial bacteria. Strains PA23 and DF41 produce antibiotics and enzymes that control fungal growth, and therefore disease. Our research is focused on understanding how genes responsible for disease control (biocontrol) are regulated. We will investigate how a new regulator of gene expression, called PtrA, controls production of antibiotics and enzymes in PA23 and DF41. In addition, we will look at the manner in which these antibiotics are exported outside of the bacterial cell. The chemical structure of the antibiotic produced by DF41 is currently not known, so we will deduce its structure. In the environment nutrients are scarce; consequently, we will investigate the impact of limited food availability on expression of genes and products required for disease suppression. These studies will shed light on how PA23 and DF41 are able to inhibit fungal growth. This will enable us to use these two bacteria as pesticide alternatives in a consistent and predictable manner.