Draft Genome Sequence of Periopathogen Tannerella forsythia Isolate 9610

Objectives: Tannerella forsythia, a Gram-negative oral anaerobe, is one of three members of the “red-complex” of periopathogens associated with development of periodontitis. Due to T. forsythia’s fastidious growth requirements, relatively little is known of it’s inter-microbial relationships and virulence mechanisms. The objective of this study is to identify and phylogenetically place a draft genome sequence of T. forsythia clinical isolate 9610.
Methods: Isolate 9610 was serially diluted on blood agar medium for a total of 3 passages, anaerobically incubated at 37°C for 3 days, then anaerobically incubated in SHI liquid media at 37°C for 3 days. The Illumina MiSeq platform was used to produce paired-end 300 bp reads, which were then assembled using SPAdes 3.9.0.
Results: The assembled genome is composed of 2,488 coding genes, 44 tRNAs, 5 rRNAs, and 1 clustered regularly interspaced short palindromic repeat (CRISPR). Phylogenetic relatives of isolate 9610 were identified by creating a 16S rRNA gene phylogenetic tree. The closest relatives were found to be T. forsythia KS16, 92A2, and ATCC 43037, with an average amino acid identity (AAI) of 98.26%, 97.93% and 97.77%, respectively. When compared to KS16, 92A2, and ATCC 43037, isolate 9610 was found to possess six unique genes in addition to polymorphisms and is missing 283 genes present in KS16.
Conclusions: These results support the identification of isolate 9610 as a novel genome within the T. forsythia species. Importantly, this study identified the presence of valine-glycine repeat protein G (VgrG), a puncturing component of the type VI secretion system (T6SS) used by Gram-negative bacteria to deliver effectors unto target cells via direct cell-cell contact. Further study is required to determine if isolate 9610 possesses other distinct components of the T6SS and, if so, how the T6SS is used for microbial competition or pathogenesis.