title: Detecting Bacterial Surface Organelles on Single Cells Using Optical Tweezers.
abstract: Bacterial cells display a diverse array of surface organelles that are important for a range of processes such as intercellular communication, motility and adhesion leading to biofilm formation, infections, and bacterial spread. More specifically, attachment to host cells by Gram-negative bacteria are mediated by adhesion pili, which are nanometers wide and micrometers long fibrous organelles. Since these pili are significantly thinner than the wavelength of visible light, they cannot be detected using standard light microscopy techniques. At present, there is no fast and simple method available to investigate if a single cell expresses pili while keeping the cell alive for further studies. In this study, we present a method to determine the presence of pili on a single bacterium. The protocol involves imaging the bacterium to measure its size, followed by predicting the fluid drag based on its size using an analytical model, and thereafter oscillating the sample while a single bacterium is trapped by an optical tweezer to measure its effective fluid drag. Comparison between the predicted and the measured fluid drag thereby indicate the presence of pili. Herein, we verify the method using polymer coated silica microspheres and Escherichia coli bacteria expressing adhesion pili. Our protocol can in real time and within seconds assist single cell studies by distinguishing between piliated and nonpiliated bacteria.
authors.affiliation: Department of Physics, and ‡Department of Chemistry, Umeå University , 901 87 Umeå, Sweden.
authors.forename: Johan
authors.initials: J
authors.lastname: Zakrisson
authors.affiliation: Department of Physics, and ‡Department of Chemistry, Umeå University , 901 87 Umeå, Sweden.
authors.forename: Bhupender
authors.initials: B
authors.lastname: Singh
authors.affiliation: Department of Physics, and ‡Department of Chemistry, Umeå University , 901 87 Umeå, Sweden.
authors.forename: Pontus
authors.initials: P
authors.lastname: Svenmarker
authors.affiliation: Department of Physics, and ‡Department of Chemistry, Umeå University , 901 87 Umeå, Sweden.
authors.forename: Krister
authors.initials: K
authors.lastname: Wiklund
authors.affiliation: Department of Physics, and ‡Department of Chemistry, Umeå University , 901 87 Umeå, Sweden.
authors.forename: Hanqing
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Department of Physics, and ‡Department of Chemistry, Umeå University , 901 87 Umeå, Sweden.
authors.forename: Shoghik
authors.initials: S
authors.lastname: Hakobyan
authors.affiliation: Department of Physics, and ‡Department of Chemistry, Umeå University , 901 87 Umeå, Sweden.
authors.forename: Madeleine
authors.initials: M
authors.lastname: Ramstedt
authors.affiliation: Department of Physics, and ‡Department of Chemistry, Umeå University , 901 87 Umeå, Sweden.
authors.forename: Magnus
authors.initials: M
authors.lastname: Andersson
mesh_terms: D018441:Biofilms; D004926:Escherichia coli / Q000166:cytology* / Q000502:physiology; D010861:Fimbriae, Bacterial / Q000378:metabolism; D052898:Optical Tweezers; D015388:Organelles / Q000378:metabolism*; D059010:Single-Cell Analysis / Q000295:instrumentation*