CNRI / SCIENCE PHOTO LIBRARY CNRI / SCIENCE PHOTO LIBRARY
Transmission electron micrograph (TEM) of the gram-positive bacteria Streptococcus pneumoniae (the pneumonococcus), a cause of pneumonia in humans. The spherical bacteria secrete a viscous material to form a capsule around their cell wall. The role of the capsule is uncertain, but is associated with virulence in pathogenic organisms. It gives the bacteria protection against the immune system of an invaded host (animal or human). Capsulated organisms resist phagocytosis (engulfing) by scavenging macrophages and continue to multiply. Magnification: x6000 at 35mm size, x12,000 at 6x7cm size.
Model release not required. Property release not required.