Inactivation of swmA results in the loss of an outer cell layer in a swimming synechococcus strain.
The mechanism of nonflagellar swimming of marine unicellular cyanobacteria remains poorly understood. SwmA is an abundant cell surface-associated 130-kDa glycoprotein that is required for the generation of thrust in Synechococcus sp. strain WH8102. Ultrastructural comparisons of wild-type cells to a mutant strain in which the gene encoding SwmA has been insertionally inactivated reveal that the mutant lacks a layer external to the outer membrane. Cryofixation and freeze-substitution are required for the preservation of this external layer. Freeze fracturing and etching reveal that this additional layer is an S-layer. How the S-layer might function in motility remains elusive; however, this work describes an ultrastructural component required for this unique type of swimming. In addition, the work presented here describes the envelope structure of a model swimming cyanobacterium.
McCarren
J
J
Marine Biology Research Division, Scripps Institution of Oceanography, University of California-San Diego, 3135 Hubbs Hall, 8750 Biological Grade, La Jolla, CA 92093-0202, USA.
Heuser
J
J
Roth
R
R
Yamada
N
N
Martone
M
M
Brahamsha
B
B
D001426:Bacterial Proteins / Q000502:physiology*; D002135:Calcium-Binding Proteins / Q000502:physiology*; D002462:Cell Membrane / Q000648:ultrastructure*; D005614:Freeze Fracturing; D046940:Synechococcus / Q000648:ultrastructure*
D001426:Bacterial Proteins; D002135:Calcium-Binding Proteins; C100438:SwmA protein, Synechococcus