Defense Date


Document Type


Degree Name

Master of Science



First Advisor

Janina Lewis


Periodontitis affects 10 to 15 percent of most adult populations and can contribute to numerous systemic diseases. Porphyromonas gingivalis, a gram-negative anaerobic bacterium, is a recognized prime causative agent in periodontitis. Studies have shown a number of small non-coding RNAs (sRNAs) have been related to bacterial virulence. Many of these sRNAs require the facilitation of the bacterial Sm-like protein, Hfq, for optimum function. Hfq is a RNA chaperone involved in RNA stability, sRNA function, and polyadenylation. Mutants lacking in Hfq often show pleiotropic phenotypes, although the extent and severity of hfq null phenotypes is often species-specific. Hfq has been encoded by nearly half of eubacteria, including pathogens. Based on a standard BLAST search, hfq has not been detected in P. gingivalis. It is highly likely, however, that the bacterium possesses an Hfq homologue due to its importance as an overall RNA cofactor. The P. gingivalis hypothetical protein, PG0228, possesses the Sm-like protein motif, thus we believe it is an excellent Hfq candidate. Our goal was to characterize PG0228 so we can gain a better insight into the function of this hypothetical protein and determine if it indeed behaves like Hfq. Microarray analysis, growth studies, and a survival study were done on a Δ0228 mutant to determine the biological role of the protein encoded by PG0228. PG0228 was also tagged in vivo in order to determine if the protein binds to RNA. Our results show P. gingivalis deficient in PG0228 show significant similarities to other bacterium deficient in hfq. The Δ0228 strain showed significant sensitivity to host defense mechanisms and an overall gene regulation in 15% of the genome. In addition, the mutant is viable but produces a lower final cell density. Thus, we believe PG0228 is an excellent Hfq candidate, and suggest further studies will show PG0228 is an Hfq homologue.


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