Dental plaque is a biofilm consisting of a complex community of over 700 different bacterial species. Epidemiological evidence suggests that a population shift toward certain gram-negative anaerobes is responsible for the initiation and progression of periodontal diseases. Tannerella forsythia, a gram-negative, filamentous, nonmotile, anaerobic bacterium, is also considered one of the pathogens implicated in contributing to advanced forms of periodontal disease in humans and is strongly associated with cases of severe periodontitis. It is found coaggregated in periodontal pockets with other putative periodontal pathogens, such as P. gingivalis and F. nucleatum. Infection with T. forsythia induces alveolar bone resorption in a mouse infection model, in which the bacterium is inoculated under the gums of mice, followed by measurement for loss of dental bone.
A. Considering all of the above information, which of Koch’s postulates as defined in Table 6–1, if any, have been satisfied so far for T. forsythia involvement in periodontal disease? Be sure to state your rationale. Provide at least two additional modern molecular experiments (different from those already described above) that could be performed to help satisfy Koch’s postulates for the involvement of each bacterial species in periodontal disease.
Table 6–1
B. Considering that periodontal disease might be a community shift-type disease with multiple microbial participants, how might you use microbialcommunity-profiling methods to demonstrate the importance of the microbial-community composition in contributing to the onset and maintenance of the diseased state? Set up the experiment first without using DNA-sequencing approaches and then using DNA-sequencing approaches. Be sure to provide your rationale for the choice of method. From your results, how could you distinguish between a model of disease caused by a microbialcommunity shift involving multiple microbes and one involving a single pathogen, such as T. forsythia or P. gingivalis, or a combination of both T. forsythia and P. gingivalis?