title: Viscoelastic properties of levan-DNA mixtures important in microbial biofilm formation as determined by micro- and macrorheology.
abstract: We studied the viscoelastic properties of homogeneous and inhomogeneous levan-DNA mixtures using optical tweezers and a rotational rheometer. Levan and DNA are important components of the extracellular matrix of bacterial biofilms. Their viscoelastic properties influence the mechanical as well as molecular-transport properties of biofilm. Both macro- and microrheology measurements in homogeneous levan-DNA mixtures revealed pseudoplastic behavior. When the concentration of DNA reached a critical value, levan started to aggregate, forming clusters of a few microns in size. Microrheology using optical tweezers enabled us to measure local viscoelastic properties within the clusters as well as in the DNA phase surrounding the levan aggregates. In phase-separated levan-DNA mixtures, the results of macro- and microrheology differed significantly. The local viscosity and elasticity of levan increased, whereas the local viscosity of DNA decreased. On the other hand, the results of bulk viscosity measurements suggest that levan clusters do not interact strongly with DNA. Upon treatment with DNase, levan aggregates dispersed. These results demonstrate the advantages of microrheological measurements compared to bulk viscoelastic measurements when the materials under investigation are complex and inhomogeneous, as is often the case in biological samples.
authors: Faculty of Mathematics and Physics, University of Ljubljana, Ljubljana, Slovenia.
authors: Biljana
authors: B
authors: Stojković
authors: Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia.
authors: Simon
authors: S
authors: Sretenovic
authors: Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia.
authors: Iztok
authors: I
authors: Dogsa
authors: Faculty of Mathematics and Physics, University of Ljubljana, Ljubljana, Slovenia.
authors: Igor
authors: I
authors: Poberaj
authors: Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia. Electronic address: david.stopar@bf.uni-lj.si.
authors: David
authors: D
authors: Stopar
mesh_terms: D000818:Animals; D001419:Bacteria / Q000378:metabolism*; D018441:Biofilms / Q000254:growth & development*; D004247:DNA / Q000737:chemistry*; D004548:Elasticity; D005399:Fishes; D005630:Fructans / Q000737:chemistry*; D008297:Male; D008857:Microscopy, Interference; D012212:Rheology; D012996:Solutions; D014783:Viscosity
chemical_list: D005630:Fructans; D012996:Solutions; D004247:DNA; C072599:levan
references: Carbohydr Polym. 2014 Jan 30;101:29-35
references: 24299745
references: J Chem Phys. 2008 Nov 14;129(18):185103
references: 19045431
references: Langmuir. 2014 Apr 15;30(14):4172-82
references: 24654746
references: Phytopathology. 2009 Nov;99(11):1237-44
references: 19821727
references: Proc Natl Acad Sci U S A. 2010 Jun 29;107(26):11715-20
references: 20498087
references: Microb Biotechnol. 2009 Nov;2(6):634-41
references: 21255298
references: Proc Natl Acad Sci U S A. 2012 Jan 17;109(3):799-804
references: 22203973
references: Carbohydr Polym. 2013 Feb 15;92(2):1234-42
references: 23399151
references: Carbohydr Polym. 2013 May 15;94(2):882-8
references: 23544646
references: PLoS One. 2013;8(4):e62044
references: 23637960
references: Environ Microbiol Rep. 2013 Dec;5(6):778-86
references: 24249286
references: Science. 2002 Feb 22;295(5559):1487
references: 11859186
references: Biotechnol Bioeng. 2002 Nov 5;80(3):289-96
references: 12226861
references: J Microbiol Methods. 2003 Jan;52(1):69-73
references: 12401228
references: Int J Biol Macromol. 2004 Apr;34(1-2):37-41
references: 15178007
references: J Dent Res. 1974 Mar-Apr;53(2):442-6
references: 4521906
references: Adv Appl Microbiol. 1990;35:171-94
references: 2205081
references: Nucleic Acids Res. 2006;34(2):564-74
references: 16449200
references: J Cosmet Sci. 2005 Nov-Dec;56(6):395-406
references: 16538295
references: Microbiology. 2006 Oct;152(Pt 10):2909-18
references: 17005972
references: Anal Bioanal Chem. 2014 Feb;406(6):1597-605
references: 24121433