Electron microscopy has largely contributed to the study of bacterial anatomy. However, as varied alterations can occur during cell preparation, at the level of cell structure and at the molecular level, it is difficult to know to what extent electron micrographs correspond to the true appearance of the living state. The recent development of cryomethods which avoid some of the alterations which may occur during conventional fixation and embedding procedures, has shed new light on bacterial anatomy. These have definitively proved that mesosomes do not exist, but are artefactual structures induced by the fixative. New features of the bacterial "nucleus" relating to its shape and fine structure appeared in thin sections of Gram-positive and Gram-negative bacteria prepared by cryosubstitution. New information has also been obtained on the cell wall structure of different bacterial species.

Bacteria↗

PubMedDate not supplied

Contribution of electron microscopy in the study of the interactions between pathogenic bacteria and their host cells.

Our knowledge on the functional anatomy of bacteria is based on the electron microscopic (EM) studies performed during the last forty years. Most pathogenic properties however cannot be visualized in EM because they are not related to defined structures. In contrast, EM studies have provided important data on the behaviour of pathogenic bacteria in their host cells. They have shown that many bacterial species have developed different stratagems to survive and multiply in their host cell. Some are even able to use the host cell machinery to move and invade adjacent cells.

Animals↗

PubMedDate not supplied

Ultrastructural study of the interaction of the fungi Sporothrix schenckii and Ceratocystis stenoceras with bone-marrow-derived murine macrophages.

Bone-marrow-derived macrophages of C57BL/6 mice cultivated in vitro were infected with the yeast form of Sporothrix schenckii or Ceratocystis stenoceras. Observations made in light and electron microscopy showed that part of the S. schenckii-containing phagosomes rapidly fused with lysosomes and fungal cells were digested. Surviving fungal cells elongated very rapidly and were liberated into the culture medium after 48 h upon macrophage lysis. The cells of the non-pathogenic isolate C. stenoceras did not elongate and were almost all digested after 8 days, while macrophages were unaltered. Staining for acid phosphatase showed that this enzymatic activity increased soon after ingestion with both isolates. However, this increase was less pronounced with S. schenckii than with the non-pathogenic isolate. The search for a toxic substance produced by S. schenckii and responsible for the low content in acid phosphatase and subsequent macrophage lysis remained negative. It is thus probable that both phenomena essentially resulted from fungus filamentation which led to a dramatic distortion of phagosomes and host cells.

Acid Phosphatase↗

PubMedDate not supplied

Plasmid-mediated intracellular multiplication of Shigella flexneri.

Explore the source record for details and available documents.

Animals↗