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T2-08 Complete Genome Sequence of the Thermotolerant Foodborne Pathogen Salmonella enterica Serovar Senftenberg ATCC 43845 and Phylogenetic Analysis of Loci Encoding Thermotolerance

Monday, July 10, 2017: 10:45 AM
Room 16 (Tampa Convention Center)
Scott Nguyen , USDA ARS U.S. Meat Animal Research Center , Clay Center , NE
James Bono , USDA ARS U.S. Meat Animal Research Center , Clay Center , NE
Timothy Smith , USDA ARS U.S. Meat Animal Research Center , Clay Center , NE
Gregory Harhay , USDA ARS U.S. Meat Animal Research Center , Clay Center , NE
Dayna Harhay , USDA ARS U.S. Meat Animal Research Center , Clay Center , NE
Audio File Recorded Presentation
Introduction: Previous studies in Cronobacter sakazakii, Klebsiella spp., and Escherichia coli have identified a genomic island that confers thermotolerance to its hosts. This island has recently been identified in Salmonella enterica serovar Senfentenberg ATCC 43845, a historically important, heat resistant isolate. Comprehensive analyses of the genetic mechanisms contributing to the thermotolerance of this strain have been impaired, as the complete genome sequence has not, previously, been available.

Purpose: This study was undertaken to characterize the complete genome sequence of Salmonella Senftenberg ATCC 43845, in order to facilitate our understanding of the genetic determinants contributing to the thermotolerance of this strain, and to conduct a phylogenetic analysis of thermotolerance loci, in order to examine their distribution among the Proteobacteria.

Methods:   Long-read, single molecule, real time sequencing technology was used to obtain the complete chromosome and finished quality assembly of Salmonella Senftenberg ATCC 43845. Thermal tolerance loci identified in Salmonella Senftenberg were used to identify related islands in the GenBank nr (nonredundant) database using BLASTn. Loci were aligned using MAFFT and the resulting aligned sequences were analyzed by jModelTest 2 to determine parameters for MrBayes 3.2.6 analysis, which was used to calculate a Bayesian inference tree of the loci.

Results: Complete genome sequence analysis revealed that Salmonella Senftenberg ATCC 43845 contains not one, but two copies of a thermotolerance island on a 341.3 kb IncHI2 plasmid. Phylogenetic analysis of these loci revealed three clades with a sparse, yet broad distribution in the Proteobacteria and sheds light on the evolution and distribution of loci conferring resistance to environmental stressors such as heat and desiccation.

Significance: This is the first report that Salmonella Senftenberg ATCC 43845 contains not one, but two copies of a thermotolerance island on a 341.3 kb IncHI2 plasmid. The data presented expand our understanding of the distribution and evolution of genetic mechanisms of heat resistance in foodborne bacterial contaminants.

Back to: Technical Session 2 - Molecular Analytics, Genomics, and Microbiome
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