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The electron microscopic structure, molecular biology and function of the crystalline surface proteins of the bacterial cell walls

Kari Lounatmaa, Ph. D., Docent

Institute of Biotechnology
Electron Microscopy Unit
Phone: 358-9-708 59503
Fax: 358-9-708 59498

Previous and current research

Bacterial surface structures are of considerable interest because these structures often have a key role in the interaction of the bacterial cell with its surroundings. Many of the surface structures, such as capsules and fimbriae, are recognized as important virulence factors of various species. During the last ten years, another bacterial surface structure has increasingly become a focus of interest, crystalline proteinaceous surface layers, S-layers. Early studies on S-layers concentrated mostly on bacteria of non-human origin. However, recently, several gram-positive and gram-negative species found in clinical infections in humans have been shown to possess an S-layer. Corynebacterium diphtheriae and Bacillus anthracis are probably the best known human pathogens with an S-layer, but new S-layered species are regularly found, especially from the oral cavity. So far little is known about the role of this layer for bacterial ecology and virulence in opportunistic infections of man. Our results indicate that the S-layers are major determinants of cell surface hydrophobicity and are involved in resistance to phagocytosis.

Future projects

- structure of S-layer from new species

- role of S-layer in bacterial binding to host molecules


To understand the role of the S-proteins in bacterial ecology and virulence.


Markus Haapasalo, DDS, Ph. D.; Eero Kerosuo, DDS, Ph. D.; Anja Kotiranta,

DDS; Kirsti Kari, M.Sci.

Selected Publications

Lounatmaa, K., M. Haapasalo. E. Kerosuo and H. Jousimies-Somer. S-layers found on clinical isolates. In: Advances in Bacterial Paracrystalline Surface Layers, edited by T.J. Beveridge and S.F. Koval, Plenum Press, New York, 33-43, 1993.

Kotiranta, A., M. Haapasalo, K. Lounatmaa and K. Kari. Crystalline surface protein of Peptostreptococcus anaerobius. Microbiol. 140: 1065-1073, 1995.

Kotiranta, A., K. Lounatmaa, K. Kari, E. Kerosuo and M. Haapasalo. Function of the S-layer of some gram-positive bacteria in phagocytosis. FEMS Microbiology Review 20: 110-114, 1997.


Academy of Finland, Finnish Dental Society, University of Oslo

Last update 01.07.1998 Maintained by Jari Ylšnne (