Structural and Mechanical Properties of Klebsiella pneumoniae Type 3 Fimbriae

Feng-Jung Chen, Chia-Han Chan, Ying-Jung Huang, Kuo-Liang Liu, Hwei-Ling Peng, Hwan-You Chang, Gunn-Guang Liou, Tri-Rung Yew, Cheng-Hsien Liu, Ken Y. Hsu, and Long Hsu
This study investigated the structural and mechanical properties of Klebsiella pneumoniae type 3 fimbriae, which constitute a known virulence factor for the bacterium. Transmission electron microscopy and optical tweezers were used to understand the ability of the bacterium to survive flushes. An individual K. pneumoniae type 3 fimbria exhibited a helix-like structure with a pitch of 4.1 nm and a three-phase force-extension curve. The fimbria was first nonlinearly stretched with increasing force. Then, it started to uncoil and extended several micrometers at a fixed force of 66 ± 4 pN (n = 22). Finally, the extension of the fimbria shifted to the third phase, with a characteristic force of 102 ± 9 pN (n = 14) at the inflection point. Compared with the P fimbriae and type 1 fimbriae of uropathogenic Escherichia coli, K. pneumoniae type 3 fimbriae have a larger pitch in the helix-like structure and stronger uncoiling and characteristic forces.

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