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Erwinia carotovora subsp. atroseptica (Eca) mutants resistant to a variety of phages were isolated and characterized, identifying lipopolysaccharide (LPS) as a frequently used phage receptor. Various strains deficient in steps in LPS assembly were isolated. One mutation mapped to horizontally acquired island (HAI) 5. Although lateral transmission of this locus to Eca has enhanced virulence in potato, it has also rendered Eca sensitive to phage infection. The genome sequence of Eca identified 17 HAIs, including 2 prophages. Genomic deletion of the prophages resulted in decreased motility, the ability of these strains to cause soft rot of potato was diminished. One phage newly isolated on Eca, φTE, was sequenced. Only 20% of the ORFs could be assigned a function. Characterization of this phage demonstrated that infection depended on the presence of a flagellum. This phage was able to mediate generalized transduction, indicating a potential use in functional genomic analysis. The generalized transducing phage that infects Serratia sp. ATCC39006 (φ0T8) was also shown to be flagellatropic following mutational analysis of the host. Further characterization of this phage identified an alternative and unexpected host, Pantoea agglomerans. It was possible to move a plasmid-encoded antibiotic resistance determinant between the two bacterial genera with high efficiency by φ0T8-mediated transduction. This φ0T8-sensitive strain of P. agglomerans has antifungal capacity, and is therefore of potential application as a biocontrol agent. The antifungal activity was investigated. P. agglomerans was found to produce an N-acyl homoserine lactone signalling molecule that is typically used in quorum sensing. The potential impact of quorum sensing on antifungal production was investigated via mutagenesis. |
