Characterization of a plasmid region involved in Bacillus anthracis toxin production and pathogenesis

• Published in: International journal of medical microbiology Vol. 290; no. 4; pp. 313 - 316
• Main Authors: Sirard, J.-C., Guidi-Rontani, C., Fouet, A., Mock, M.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Jena Elsevier GmbH 01.10.2000; Elsevier
• Subjects: Antigens, Bacterial; Bacillus anthracis - pathogenicity; Bacterial Toxins - biosynthesis; Bacterial Toxins - genetics; Bacterial Toxins - toxicity; Bacteriology; Base Sequence; Biological and medical sciences; Chromosome Mapping; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Bacterial; Genetics; germination; Humans; macrophages; Macrophages - microbiology; Microbiology; Molecular Sequence Data; phagolysosome; Plasmids; regulation of expression; resolvase; Spores, Bacterial - physiology; transposase; virulence factors; germination; phagolysosome; macrophages; regulation of expression; resolvase; transposase; virulence factors; Bacillus anthracis; Germination; Gene organization; Bacillaceae; Gene expression; Spores; Plasmid; Pathogenicity; Toxin; Regulation(control); Bacillales; Bacteria; Trans acting regulatory factor; Macrophage
• ISSN: 1438-4221; 1618-0607
• DOI: 10.1016/S1438-4221(00)80030-2

The germination of spores within the host is the initial step of anthrax infection. We have shown, using immunofluorescence staining, confocal scanning laser microscopy and image cytometry analysis, that the alveolar macrophage is the primary site of B. anthracis germination in a murine inhalation infection model. B. anthracis germinated inside macrophages, in vesicles derived from the phagosomal compartment. We have demonstrated that the toxin genes and their trans-activator, AtxA, are expressed within the macrophages after germination. It was also shown that the pXOl plasmid strongly enhanced capsule formation and that this influence is mediated by AtxA. This indicates the existence of a regulon where AtxA is the regulatory protein acting on genes located on different plasmids. We identified a tricistronic germination operon gerX located between the pag and atxA genes on the 40-kb toxin-encoding fragment of pXO1. Analysis of a gerX null mutant indicated that gerX-encoded proteins are involved in the virulence of B. anthracis.