Three genes PG0690, PG1075 and PG1076 encoding 4-hydroxybutyrate CoA-transferase, the coenzyme A transferase beta subunit and acyl-CoA dehydrogenase (short-chain specific) respectively, that are in the pathway branch that produces butyrate, were down-regulated, find more as were a cluster of genes encoding a methylmalonyl-CoA decarboxylase (PG1608-1612) that is part of the pathway branch that produces propionate. Signal transduction, regulatory and transcription genes

It has been well established that two-component signal transduction systems (TCSTSs) play an important role in biofilm formation in many bacteria, including E. coli [45], Enterococcus faecalis [46] and Streptococcus mutans [47]. Interrogation of the P. gingivalis W83 ORFs revealed only

6 putative TCSTSs. The transcriptomic analysis indicated that one of these TCSTSs, comprising PG1431 and PG1432, that encode a DNA-binding response regulator of the LuxR MK-1775 molecular weight family and a putative sensor histidine kinase respectively, was up-regulated in biofilm cells. To date, the involvement of signal transduction, transcriptional regulators and other transcription factors in P. gingivalis biofilm development has yet to be QNZ solubility dmso established. Homologues of the TCSTSs PG1431 and PG1432 have been found in P. gingivalis strain ATCC 33277 and were designated fimR and fimS, respectively [48]. FimR and FimS are known to regulate FimA-associated fimbriation [48]. Comparative transcriptomic profiling of P. gingivalis ATCC 33277 and its fimR deficient mutant indicated only a limited number of genes were part of the fimR regulon including PG1974, PG0644 (tlr) and the first gene of the fim locus, PG2130 [49]. Binding of FimR upstream of PG2130 initiates an expression cascade involving PG2131-34. The transcriptomic data presented here do concur with the possible positive regulation

of PG1974 by PG1431, however, they are in conflict with the role of PG1431 in the positive regulation of the fim locus because in strain W50 biofilms we observed decreased enough expression of PG2133 and PG2134 with no differential expression of fimA. Thus, the role of PG1431 and PG1432 in P. gingivalis W50 biofilm growth may not be reflected in the earlier study of P. gingivalis ATCC 33277 FimS and FimR mutants. It is predicted that there are 29 orphan transcriptional regulatory proteins in P. gingivalis but only 4 of these were differentially regulated in biofilm cells, one of which was the down-regulated PG0270, oxyR. The remaining three possible transcriptional regulators PG0173, PG0826 (of the AraC family of transcriptional regulators) and PG2186 were found to be up-regulated. Members of the AraC family of transcriptional regulators have been shown to be important in carbon metabolism, stress response and virulence in other species (for review see Gallegos), [50] and in the regulation of quorum sensing signaling in P. aeruginosa [51].