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P2-131 Phylogenomic Analyses of Type II Toxin-Antitoxin Genes in the Foodborne Pathogen Cronobacter spp. Using Sequenced-based Bioinformatics Combined with DNA Microarray Analysis Demonstrates an Evolutionary Shared Species-Specific Line of Evolution

Tuesday, July 11, 2017
Exhibit Hall (Tampa Convention Center)
Samantha Finkelstein , U.S. Food and Drug Administration , Laurel , MD
Jayanthi Gangiredla , U.S. Food and Drug Administration , Laurel , MD
Flavia Negrete , U.S. Food and Drug Administration , Laurel , MD
Hannah Chase , U.S. Food and Drug Administration , Laurel , MD
ChaeYoon Lee , U.S. Food and Drug Administration , Laurel , MD
HyeJin Jeong , U.S. Food and Drug Administration , Laurel , MD
Isha Patel , U.S. Food and Drug Administration , Laurel , MD
Gopal Gopinath , U.S. Food and Drug Administration , Laurel , MD
Ben Tall , U.S. Food and Drug Administration , Laurel , MD
Introduction: Cronobacter spp. an etiologic agent of infantile foodborne outbreaks can survive extreme desiccation conditions, thus favoring its persistence in powdered infant formula and dry environments. Expression of toxin-antitoxin type II (TA) systems is thought to modulate bacterial physiology and survival during periods of stressful growth conditions.  The phylogenetic landscape of TA loci among Cronobacter spp. is poorly understood.

Purpose: This investigation was conducted to provide a deeper understanding of the phylogeny of TAs found among Cronobacter spp. 

Methods: One hundred forty-three WGS assemblies were uploaded to the web-based TAfinder tool at http://202.120.12.135/TADB2/index.php to identify TA loci. Additional analyses were conducted using a pan-genomic DNA microarray (MA).  Sequences of these loci were then used to confirm presence of TA alleles on the microarray and in phylogenetic analysis using CLC Genomics workbench and MEGA7.

Results: On average approximately six TAs such as relE-xre, COG5654-xre, fic-phd, fic-yhfG, and hipA loci with BLAST scores of >90% were found.  Fifty-five TA alleles were confirmed to be present on the microarray which represented six of the seven Cronobacter spp. Twenty-six duplicated alleles were removed from MA which showed that in some, but not all species, the TA allelic sequence divergence aligned with species taxa lines. For example, MA showed that 10 C. malonaticus strains clustered with some C. sakazakii strains signifying that sequence divergence of some TAs between these two species share a common phylogenetic history. WGS analysis of fic-like and a hipA-like orthologues of the seven species supported the phylogenetic relationship found by MA.

Significance: Understanding TAs among Cronobacter spp. is essential to design future studies identifying mechanisms used for survival and persistence in foods. These results demonstrate that in some species, TA alleles share a common phylogeny, while in other species, they follow species-specific phylogeny.  Their identification is critical for reliable prediction of gene function.

Back to: Poster Session 2 – Food Chemical Hazards and Food Allergens, Food Toxicology, Meat, Poultry and Eggs, Epidemiology, Retail and Food Service Safety, Communication Outreach and Education, Molecular Analytics, Genomics and Microbiome, Laboratory and Detection Methods, and Dairy
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