Investigating the Surface Structure and Antibody Recognition Forces of Tannerella Forsythia by Scanning Probe Microscopy

Abstract

Tannerella forsythia ATCC 43037 (Tf) is a Gram-negative oral anaerobe which is one of the major contributors to periodontal disease in humans [1]. It possesses a glycosylated S-layer consisting of two regularly arrayed subunits as outermost cell envelope layer. The S-layer of Tf was shown to be a virulence factor, capable of delaying the bacterium's recognition by the innate immune system [2] and mediating adhesion and invasion of host cells [3]. In this study, we used scanning probe microscopy to probe the S-layer surface of live Tf cells by investigating the nano subunit structure so as to characterize the surface structure and the interactions of Tf S-layer proteins. High-resolution imaging of living Tf wild-type cells has shown a periodic square lattice structure with about 10 nm dimension, while on the surface of an S-layer single mutant no periodic structure was visible. In addition, single-molecule force spectroscopy using a TfsA S-layer protein specific antibody immobilized onto AFM tips revealed specific interaction forces with the S-layer structure on living Tf wild-type cells. Our data contribute to the elucidation of a surface structure on living bacteria and to the understanding of their subunit arrangement with nano-meter resolution.[1] S. Holt, and J. Ebersole Periodontology 2000 38 (2000) 72.[2] G. Sekot, G. Posch, P. Messner, M. Matejka, X. Rausch-Fan, O. Andrukhov, and C. Schaffer, J. Dent, Res 90 (2011) 109[3] J. Sakakibara, K. Nagano, and Y. Murakami, Microbiology 153 (2007) 866.