Project description:Salmonella enterica serovar Typhimurium (S. Typhimurium) definitive phage type 104 (DT104) has caused significant morbidity and mortality in humans and animals for almost three decades. We have completed the full DNA sequence of one DT104 strain, NCTC13348 and show that the main differences between the genome of this isolate and the previously sequenced S. Typhimurium LT2 lie in integrated prophage elements and the Salmonella Genomic Island 1 encoding antibiotic resistance genes. Thirteen isolates of S. Typhimurium DT104 with different pulsed field gel electrophoresis (PFGE) profiles were analyzed by multi locus sequence typing (MLST), plasmid profiling, hybridization to a Pan-Salmonella DNA microarray and prophage-based multiplex PCR. All the isolates belonged to a single MLST type ST19. Microarray data demonstrated that the 13 DT104 isolates were remarkably conserved in gene content. The PFGE band-size differences in these isolates could be explained to a great extent by changes in prophage and plasmid content. Thus, here the nature of variation in different S. Typhimurium DT104 isolates is further defined at the genome level illustrating how this phage type is evolving over time.
Project description:The 240-kb Salmonella phage SPN3US genome encodes 264 gene products, many of which are functionally uncharacterized. We have previously used mass spectrometry to define the proteomes of wild-type and mutant forms of the SPN3US virion. In this study we sought to determine if this technique was suitable for the characterization of the SPN3US proteome during liquid infection. Mass spectrometry of SPN3US-infected cells identified 232 SPN3US and 1994 Salmonella proteins. SPN3US proteins with related functions, such as proteins with roles in DNA replication, transcription and virion formation, were coordinately expressed in a temporal manner. Mass spectral counts showed the four most abundant SPN3US proteins to be the major capsid, two head ejection proteins, and the functionally unassigned protein, gp22. This high abundance of gp22 in infected bacteria contrasted with its absence from mature virions, suggesting it might be the scaffold protein, an essential head morphogenesis protein yet to be identified in giant phages. These studies demonstrate the power of mass spectral analyses for facilitating the acquisition of new knowledge into the molecular events of viral infection.
