Charting and unzipping the surface layer of Corynebacterium glutamicum with the atomic force microscope.
Bacterial surface layers (S-layers) are extracellular protein networks that act as molecular sieves and protect a large variety of archaea and bacteria from hostile environments. Atomic force microscopy (AFM) was used to asses the S-layer of Coryne-bacterium glutamicum formed of PS2 proteins that assemble into hexameric complexes within a hexagonal lattice. Native and trypsin-treated S-layers were studied. Using the AFM stylus as a nanodissector, native arrays that adsorbed to mica as double layers were separated. All surfaces of native and protease-digested S-layers were imaged at better than 1 nm lateral resolution. Difference maps of the topographies of native and proteolysed samples revealed the location of the cleaved C-terminal fragment and the sidedness of the S-layer. Because the corrugation depths determined from images of both sides span the total thickness of the S-layer, a three-dimensional reconstruction of the S-layer could be calculated. Lattice defects visualized at 1 nm resolution revealed the molecular boundaries of PS2 proteins. The combination of AFM imaging and single molecule force spectroscopy allowed the mechanical properties of the Corynebacterium glutamicum S-layer to be examined. The results provide a basis for understanding the amazing stability of this protective bacterial surface coat.
Scheuring
Simon
S
M. E. Müller Institute for Microscopy at the Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056, Switzerland.
Stahlberg
Henning
H
Chami
Mohamed
M
Houssin
Christine
C
Rigaud
Jean-Louis
JL
Engel
Andreas
A
D001425:Bacterial Outer Membrane Proteins / Q000648:ultrastructure; D002473:Cell Wall / Q000187:drug effects / Q000648:ultrastructure*; D003352:Corynebacterium / Q000737:chemistry / Q000187:drug effects / Q000648:ultrastructure*; D018625:Microscopy, Atomic Force; D008956:Models, Chemical; D013499:Surface Properties; D014357:Trypsin / Q000494:pharmacology
D001425:Bacterial Outer Membrane Proteins; D014357:Trypsin