title: Extracellular matrix reorganization during cryo preparation for scanning electron microscope imaging of Staphylococcus aureus biofilms.
abstract: Biofilms are three-dimensional communities of bacteria distributed in a highly hydrated extracellular matrix (ECM). They can be visualized by scanning electron microscopy (SEM), but the requisite SEM sample preparation can modify the biofilm morphology. Here, four different approaches to prepare biofilms of hydrated Staphylococcus aureus for SEM imaging are compared. In order of increasing cooling effectiveness these are: (1) drying in air; (2) plunging in liquid nitrogen; (3) plunging in liquid ethane; and (4) high pressure freezing with liquid nitrogen. These different methods give rise to markedly different biofilm morphologies, which are revealed by cryo-SEM imaging. Significantly, high-pressure frozen biofilms exhibit a rich network of nanoscale ECM fibers surrounding individual bacteria throughout the biofilm thickness. This structure is entirely lost when similar biofilms are dried in air, and it is substantially modified when these biofilms are plunged into liquid nitrogen or liquid ethane.
authors.affiliation: 1Department of Chemical Engineering and Materials Science,Stevens Institute of Technology,Hoboken,NJ 07030,USA.
authors.forename: Yong
authors.initials: Y
authors.lastname: Wu
authors.affiliation: 1Department of Chemical Engineering and Materials Science,Stevens Institute of Technology,Hoboken,NJ 07030,USA.
authors.forename: Jing
authors.initials: J
authors.lastname: Liang
authors.affiliation: 2Leica Microsystems Inc.,1700 Leider Lane,Buffalo Grove,IL 60089,USA.
authors.forename: Kim
authors.initials: K
authors.lastname: Rensing
authors.affiliation: 1Department of Chemical Engineering and Materials Science,Stevens Institute of Technology,Hoboken,NJ 07030,USA.
authors.forename: Tseng-Ming
authors.initials: TM
authors.lastname: Chou
authors.affiliation: 1Department of Chemical Engineering and Materials Science,Stevens Institute of Technology,Hoboken,NJ 07030,USA.
authors.forename: Matthew
authors.initials: M
authors.lastname: Libera
mesh_terms: D001431:Bacteriological Techniques / Q000379:methods*; D018441:Biofilms; D005109:Extracellular Matrix / Q000528:radiation effects* / Q000648:ultrastructure*; D008855:Microscopy, Electron, Scanning; D013211:Staphylococcus aureus / Q000502:physiology* / Q000648:ultrastructure*