Potential usefulness of SNP in the 16S rRNA gene serving as informative microbial marker for forensic attribution

The field of microbial forensics focuses on the attribution of numerous microbes used by perpetrators inbiocrime and bioattack, including many foodborne pathogens such as Escherichia coli O157:H7 caused serious zoonotic disease. Recent source tracing analysis with the 16S rRNA gene, even genome-wide variations of a pathogen, is increasing as sequencing technologies advance. By using whole genome sequence analysis, more SNPs have been used to create a very finely resolved phylogenetic tree for discriminating close evolutionary relationship among strains. In our study, 1401bp of 16S rRNA gene in Enterohemorrhagic Escherichia coli (EHEC) O157:H7 strains were sequenced. The result showed that nucleotide transition and nucleotide transversion happened at 14 positions of sequence in the research strains, and variation of seven positions was located at one of nine separate hypervariable regions (V7). Another SNP within the constant region of 16S rRNA gene was also observed as the previous studies. Through comparing the available sequences obtained from the NCBI database, SNP was the only 16S rRNA polymorphism detected among the closely related EHEC O157:H7 stains. Our investigation demonstrates that unique SNPs in 16S rRNA gene have potential discriminatory power as other species-/strain-specific informative markers for attribution purpose.