Measurement of the adhesive force between a single Klebsiella pneumoniae type 3 fimbria and collagen IV using optical tweezers Bo-Jui Chang a,1 , Ying-Jung Huang b,1 , Chia-Han Chan c , Long Hsu c, * , Hwei-Ling Peng b , Hwan-You Chang d , Tri-Rung Yew e , Cheng-Hsien Liu f , Sien Chi a,g a Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu City 300, Taiwan b Department of Biological Science and Technology, National Chiao Tung University, Hsinchu City 300, Taiwan c Department of Electrophysics, National Chiao Tung University, Hsinchu City 300, Taiwan d Institute of Molecular Medicine and Department of Life Sciences, National Tsing Hua University, Hsinchu City 300, Taiwan e Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu City 300, Taiwan f Department of Power Mechanical Engineering, National Tsing Hua University, Hsinchu City 300, Taiwan g Department of Electrical Engineering, Yuan Ze University, Zhongli City, Taoyuan County 32003, Taiwan Received 22 August 2006 Available online 12 September 2006 Abstract Type 3 fimbriae are important adhesive filaments that assist Klebsiella pneumoniae to establish an infection. Different MrkD adhesin variants on the fimbriae are known to display distinct adherence capability for the bacteria to bind extracellular matrix proteins, although the difference has not been determined physically. For this reason, the adhesive force between type 3 fimbriae and collagen IV were measured using optical tweezers. The measured force data displayed a periodic histogram thus Fourier analysis was applied to group it to extract the adhesive force of a single molecular pair. Specifically, we showed that grouping should begin with an offset at the first half of the period. Finally, we first present the adhesive force between each mrkD V2 -, mrkD V3 -, and mrkD V4 -expressed fimbriae and collagen IV is 2.03, 3.79, and 2.87 pN, respectively. This result can be referred to further research on mrkD allelic effect on bacteria infection. Ó 2006 Elsevier Inc. All rights reserved. Keywords: Adhesive force; Type 3 fimbriae; Grouping offset; Klebsiella pneumoniae; Optical tweezers; Fourier analysis Klebsiella pneumoniae is an opportunistic pathogen that causes complicated urinary tract infection, pneumonia, septicemia, and liver abscess in immunocompromised patients [1,2]. The ability of many K. pneumoniae clinical isolates to colonize respiratory and urinary epithelia has been attributed to the presence of many adhesive mole- cules, including type 3 fimbriae [3]. The fimbriae, encoded by a multigene operon, contain the major subunit MrkA that forms the shaft of the fimbriae and MrkD adhesin [4]. On the tip of the fimbriae, MrkD adhesin is responsible for mediating erythrocyte agglutination in a mannose inde- pendent way [5] and could affect biofilm formation of the bacteria [6]. Although the receptor for the adhesin has yet to be identified, in vitro research indicates that bacteria expressing type 3 fimbriae are able to bind to type IV and V collagen, which may be exposed on exfoliated and denuded epithelial surfaces during infections [7]. Our analysis of K. pneumoniae clinical isolates from Tai- wan has revealed the presence of four mrkD alleles, namely mrkD v1 (GenBank Accession No. AY225462), mrkD v2 (GenBank Accession No. AY225463), mrkD v3 (GenBank Accession No. AY225464), and mrkD v4 (GenBank Acces- sion No. AY225465). To investigate the effect of the allelic variation on binding activity of the fimbriae, a type 3 0006-291X/$ - see front matter Ó 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.bbrc.2006.08.190 * Corresponding author. Fax: +886 3 5131241. E-mail address: long@cc.nctu.edu.tw (L. Hsu). 1 These authors contributed equally to this work. www.elsevier.com/locate/ybbrc Biochemical and Biophysical Research Communications 350 (2006) 33–38 BBRC