H-070. Computational Prediction of PilR-Regulated Sequence Elements in the Genome of Geobacter sulfurreducens

J. F. Barbe1, T. Ueki2, K. Juarez-Lopez3, R. M. Adkins1, D. R. Lovley2, J. Krushkal1;
1Univ. of Tennessee Hlth. Sci. Ctr., Memphis, TN, 2Univ. of Massachusetts, Amherst, MA, 3Inst. de Biotecnología/UNAM, Cuernavaca, MEXICO.

Geobacter sulfurreducens is a pure culture model representative of the family Geobacteraceae, which is a group of organisms from the delta subdivision of Proteobacteria participating in bioenergy production and in environmental bioremediation. PilR is an enhancer binding protein (EBP), which acts cooperatively with RpoN in transcriptional regulation. Both RpoN and PilR are involved in the complex regulation of expression of the pilA gene, whose product is pilin, a structural component of pili. G. sulfurreducens pili are electrically conductive nanowires that are required for Fe(III) oxide reduction and for optimal current production in microbial fuel cells. Earlier studies in other organisms suggested candidate sequence elements and/or repeated sequence patterns which may be recognized by PilR. Using sequence conservation information, pattern searches, and microarray analysis of a pilR deletion mutant, we performed in silico prediction of multiple G. sulfurreducens sequence elements, which are likely to be regulated by PilR. These sites were identified upstream of multiple genes whose products participate in biosynthesis, assembly, and function of pili and flagella, in secretary pathways, and in cell wall biogenesis. We also documented the co-occurrence of many predicted PilR regulatory sites with RpoN-regulated promoters, in agreement with the suggested involvement of both RpoN and PilR in regulation of expression of PilR-dependent genes. These computational findings of PilR-regulated sequence elements will aid in a better understanding of the intrinsic nature of molecular mechanisms regulating production and assembly of pili and flagella that are important for Fe(III) reduction and the production of electric current.