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Sarah Vanderlinde Bench B 31/08/2016

Classification

Higher order taxa

Bacteria; FCB group (Fibrobactere-Chlorobi-Bacteroidetes superphylum); Bacteroidetes; Bacteroidetes; Bacteroidales; Porphyromonadaceae; Porphyromonas

Species

Porphyromonas gingivalis, Strain W83

Description and significance

Porphyromonas gingivalis is a gram negative, rod shaped bacterium typically found in the subgingival niche of people suffering from periodontal disease ^[1]. H. Werner first isolated strain W83 in the 1950s (Bonn, Germany) from an unknown oral disease sample ^[2]. Oral samples can be cultured on horse blood agar at 37°C under anaerobic conditions to form black-pigmented colonies after 6-10 days ^[1]. P. gingivalis is a prominent and typically commensal member of the oral microbiome however under certain conditions can for a complex with other oral pathogens to produce periodontal lesions ^[2]. This complex, termed the “red complex” includes P. gingivalis, Treponema denticola, and Tannerella forsythia and has been associated with severe periodontal disease ^[2]. Periodontitis is a polymicrobial disease characterized by initial inflammation of gingival tissue which if left untreated, can lead to the eventual destruction of tooth-supporting structures and loss of teeth ^[1]. The World Health Association have stated that 10-15% of the global population suffer from periodontitis, making the study and potential targeting of its causative bacteria an essential field of biomedical research ^[3].

Genome structure

P. gingivalis strain W83 has a circular genome, 2,343,479 bp in length with an average GC content of 48.3% ^[4]. It contains 1,990 identified open reading frames (ORFs) (85% of the genome), 54% of which were determined to have biological roles. The P. gingivalis genome has four ribosomal operons (5S-23S-tRNAAla-tRNAIle-16S), 2 structural RNA genes and 53 tRNA genes with specificity for all 20 amino acids ^[4]. Approximately 6% of the genome consists of repetitive elements including DNA repeats and transposable elements. DNA repeats consisted of uninterrupted direct repeats and clustered regularly interspaced short palindromic repeats (CRISPRs). Strain W83 does not appear to contain other classes of repetitive elements such as ERIC and REP ^[4].

Cell structure and metabolism

P. gingivalis is non-motile and requires iron for growth, therefore causing it to form black colonies on blood agar after 6-10 days due to heme accumulation [1].

Ecology

P. gingivalis is an obligate anaerobe typically found in the subgingival sulcus of the human oral cavity. It is able to survive in the deep periodontal pocket due to its ability to ferment amino acids for energy production ^[1]. P. gingivalis is a secondary coloniser in dental plaque formation, often adhering to primary colonisers such as Streptococci and Actinomyces naeslundii ^[4]. As well as in the oral cavity, P. gingivalis has been found in the upper gastrointestinal tract, respiratory tract, colon and women with bacterial vaginosis ^[5].

Pathology

Recent research has shown that only a small number of bacteria found in the subgingival niche contribute to periodontitis, of which P. gingivalis is the major etiological factor. Datta et al. (2008) identified P. gingivalis in 85.75% of subgingival plaque samples from patients with chronic periodontitis. It first invades oral epithelial cells via phagosome uptake where it then activates cellular autophagy to create a replicative niche and suppress apoptosis ^[2]. Biofilm formation and bacterial dipeptidyl peptidase IV (DPPIV) also aid in P. gingivalis pathogenicity.

Application to biotechnology

Bioengineering, biotechnologically relevant enzyme/compound production, drug targets,…

Current research

Research is currently being conducted into the symbiotic relationship between bacteria that contribute to periodontal disease, in particular P. gingivalis and Aggregatibacter actinomycetemcomitans. Previous studies have found that neither of these bacteria is able to survive and cause disease without the other, therefore making their relationship of great interest. Studies are also being conducted into the structure and production of fimbriae as a potential target to prevent tooth adhesion and biofilm formation ^[7]. Recent clinical and epidemiological studies have shown that P. gingivalis may facilitate the development and progression of collagen induced arthritis ^[8]. P. gingivalis has the unique ability to express citrullinating peptidylarginine deiminase enzyme. This enzyme has the ability to convert arginine residues in proteins to citrulline and recent research has suggested that autoimmunity against citrullinated proteins may be a contributing factor to the development of rheumatoid arthritis ^[8].

References

1. [How, K. Y., Song, K. P., and Chan, K. G. (2016).Porphyromonas gingivalis: An Overview of Periodontopathic Pathogen below the Gum Line. Frontiers in Microbiology, 7, 53.]

2. [Mysak, J., Podzimek, S., Sommerova, P., Lyuya-Mi, Y., Bartoya, J., Janatova, T., Prochazkova, J and Duskova, J. 2014 Porphyromonas gingivalis: Major Periodontopathic Pathogen Overview. Journal of Immunology Research, vol. 2014, Article ID 476068, 8 pages. doi:10.1155/2014/476068]

3. [Petersen P. E. and Ogawa H. (2012) The global burden of periodontal disease: towards integration with chronic disease prevention and control. Periodontology, 2000 15–39. 10.1111/j.1600-0757.2011.00425.x]

4. [Nelson, K. E., Fleischmann, R. D., DeBoy, R. T., Paulsen, I. T., Fouts, D. E., Eisen, J. A. and Fraser, C. M. (2003) Complete Genome Sequence of the Oral Pathogenic Bacterium Porphyromonas gingivalis Strain W83. Journal of Bacteriology, 185(18), 5591–5601. http://doi.org/10.1128/JB.185.18.5591-5601.2003]

5. [Africa, C., Nel, J. and Stemmet, M. (2014) Anaerobes and Bacterial Vaginosis in Pregnancy: Virulence Factors Contributing to Vaginal Colonisation. International Journal of Environmental Research and Public Health, 7, 11, 6979–7000. doi:10.3390/ijerph110706979]

6. [Datta, H. K., Ng, W. F., Walker, J. A., Tuck, S. P. and Varanasi, S. S. (2008) The cell biology of bone metabolism. J. Clin. Pathol. 61 577–587. 10.1136/jcp.2007.048868]

7. [Lin, X., Wu, J and Xie, H. (2006) Porphyromonas gingivalis minor fimbriae are required for cell-cell interactions. Infection and Immunity, 74, 10, 6011–6015.]

8. [Kharlamova, N., Sherina, N., Quirke, A. M. and Eriksson, K. (2014) A6.8 Elevated antibody levels to porphyromonas gingivalis detected in rheumatoid arthritis patients with a specific anti-citrullinated protein/peptide antibody profile. Annals of the Rheumatic Diseases, 1, 73, A73–A74.]

This page is written by Sarah Vanderlinde for the MICR3004 course, Semester 2, 2016