Partial Characterization of Bacteriophages of Pseudomonas syringae pv. tomato

Since the first major outbreak of bacterial speck in 1978, this disease has been a major problem for tomato growers in certain regions of North America. This disease, characterized by small brown to black lesions, is caused by Pseudomonas syringae pv. tomato (Jones et. al., 1991). While bacterial speck is not a threat to the plant itself, it reduces the marketable value of the fruit by decreasing its aesthetic appeal to the consumer. The taxonomic status ofP. tomato is uncertain at present. It is difficult to distinguish morphologically and physiologically from other pathovars of the species, particularly Pseudomonas syringae pv. syringae. P. syringae pv. syringae has also been characterized from necrotic lesions on infected tomato fruit (Jones et. al., 1981). P. tomato is also of interest because it has been used as a model in plant pathogen studies with Arabidopsis thaliana, to gain a better understanding of the molecular basis of bacterial disease resistance (Whalen and Staskawicz, 1990). A comprehensive fine structure genetic analysis ofP. tomato would provide useful information for these areas of interest. Transducing bacteriophages are useful genetic tools for analyzing closely linked bacterial genes. Bacteriophages are classified as either virulent, whereby infected cells lyse with liberation of new bacteriophage particles, or temperate, in which case the infected bacteria either lyse with liberation of new bacteriophage progeny or become lysogenic (Hayes, 1968). In the lysogenic state, the bacteriophage genome, now called a prophage, replicates in tandem with the bacterial chromosome either by establishing a plasmid form or by integrating into the chromosome. Temperate bacteriophages capable of establishing lysogeny probably account for most transduction-mediated gene flow among bacteria in nature and provide systems that are most easily studied (Gerhardt et. al., 1981). The objectives of this study were to enrich for and characterize bacteriophages ofP. tomato suitable for transduction analysis. The characterization and analysis ofbacteriophage isolates is useful for taxonomic purposes because they offer valuable methods to distinguish closely related bacterial species (Cuppels, 1983). These methods include bacteriophage sensitivity tests and fine structure mapping by transduction. Bacteriophage sensitivity patChad E. Paschall University ofArkansas for Medical Sciences 4301 West Markham LittleRock, AR 72205