Treponema denticola biofilm-induced expression of a bacteriophage, toxin–antitoxin systems and transposases

Abstract

Treponema denticola is an oral spirochaete that has been strongly associated with chronic periodontitis. The bacterium exists as part of a dense biofilm (subgingival dental plaque) accreted to the tooth. To determine T. denticola gene products important for persistence as a biofilm we developed a continuous-culture biofilm model and conducted a genome-wide transcriptomic analysis of biofilm and planktonic cells. A total of 126 genes were differentially expressed with a fold change of 1.5 or greater. This analysis identified the upregulation of putative prophage genes in the T. denticola 35405 genome. Intact bacteriophage particles were isolated from T. denticola and circular phage DNA was detected by PCR analysis. This represents the first, to our knowledge, functional bacteriophage isolated from T. denticola, which we have designated Qtd1. In biofilm cells there was also an upregulation of genes encoding several virulence factors, toxinantitoxin systems and a family of putative transposases. Together, these data indicate that there is a higher potential for genetic mobility in T. denticola when growing as a biofilm and that these systems are important for the biofilm persistence and therefore virulence of this bacterium.

Virulence Factors of the Oral Spirochete Treponema denticola

“…A functional lysogenic bacteriophage, φtd1, was discovered during T. denticola biofilm growth that may be capable of transferring virulence-related genes through horizontal gene transfer. The bacteriophage is 37,920 bp in length and has a GC content of ~37%, similar to that of T. denticola (Mitchell et al, 2010). Analysis of these data together indicates that there is a higher potential for genetic mobility in T. denticola when growing as a biofilm, and that these systems are important for biofilm persistence and therefore virulence of this bacterium.…”

“…T. denticola was initially inoculated into the chemostat, and once cell density had stabilized, P. gingivalis was added to the continuous culture. (b) Electron micrograph of T. denticola biofilm formed on a glass rod submerged in continuous culture after 14 days' incubation as described previously (Mitchell et al, 2010). Outer sheath vesicles are indicated by arrows.…”

“…This system was then used specifically to determine the effects of biofilm growth relative to the planktonic state. In the biofilm, 126 T. denticola genes were differentially expressed, with a fold change of 1.5 or greater (Mitchell et al, 2010). In biofilm cells, there was an up-regulation of genes encoding several putative virulence factors, including cystalysin and the outer membrane dentilisin protease lipoprotein complex, toxinantitoxin systems, and a family of putative transposases (Mitchell et al, 2010).…”

“…Twenty-five of the 35 putative transposase genes were significantly up-regulated in the biofilm relative to planktonic cells. This could lead to extensive chromosomal re-arrangement, resulting in the development of population-level diversity, or may represent a novel gene-regulatory mechanism (Mitchell et al, 2010). A functional lysogenic bacteriophage, φtd1, was discovered during T. denticola biofilm growth that may be capable of transferring virulence-related genes through horizontal gene transfer.…”

Possibilities of Molecular-Genetic Tests in Periodontology

“…Results of numerous domestic and foreign authors studies show, that the periodontal diseases leading etiological factor are periopathogenic bacteria [2][3][4][5]. Most of them are anaerobes, characterized by high adhesiveness, invasiveness and toxicity.…”