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Updated: Jun 9, 2026
Sample Preparation for Single Virion Atomic Force Microscopy and Super-resolution Fluorescence Imaging
Published on: January 2, 2014
Structural analysis of a Synechococcus myovirus S-CAM4 and infected cells by atomic force microscopy
Yuri G Kuznetsov1, Jennifer B H Martiny, Alexander McPherson
1Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697-3900, USA.
Abstract:
A tailed cyanophage, S-CAM4 (family Myoviridae) from California coastal waters that infects Synechococcus, was characterized by atomic force microscopy. Capsomeric clusters of protein composing the 85 nm diameter icosahedral head were resolved and indicated a triangulation number of T=16. The 140 nm tail assembly, exhibiting a helical appearance with a 13 nm pitch, was seen in both extended and contracted states, the latter exposing the injection tube within. Attached below the base plate were six 50 nm long fibres, and six fibres 275-300 nm in length protruded from the periphery of the base plate. Protein-free DNA was abundant from ruptured heads. Virus attached en masse, in clusters and individually to cells, and cell fragments were recorded, as were perforated cells lysed by the phages. The capsid structure appears most closely related to that of the cyanophage Syn9 and the Bacillus subtilis phage SPO1, which may, in turn, be evolutionarily related to herpesvirus.
Insights
This study details the atomic force microscopy of S-CAM4, a cyanophage infecting Synechococcus. Its detailed structure, including head, tail, and fibers, was resolved, revealing insights into viral infection mechanisms.
Area of Science:
- Microbiology
- Virology
- Structural Biology
Background:
- Cyanophages are viruses that infect cyanobacteria, playing crucial roles in marine ecosystems.
- Understanding phage structure is key to deciphering infection mechanisms and evolutionary relationships.
Purpose of the Study:
- To characterize the morphology of the tailed cyanophage S-CAM4 using atomic force microscopy.
- To elucidate the structural details of the phage head, tail, and baseplate fibers.
Main Methods:
- Atomic force microscopy (AFM) was employed to visualize the S-CAM4 virion.
- Detailed measurements of the icosahedral head, helical tail, and baseplate fibers were obtained.
Main Results:
- The 85 nm icosahedral head showed T=16 triangulation. The 140 nm tail exhibited helical symmetry with a 13 nm pitch.
- Distinct head and tail structures, including an exposed injection tube in the contracted state, were resolved.
- Multiple tail fibers of varying lengths were observed, crucial for cell attachment.
Conclusions:
- The structural analysis of S-CAM4 provides a detailed understanding of its morphology.
- S-CAM4 shares structural similarities with other cyanophages and potentially evolutionary links to herpesviruses.
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