Anthrax: Biology of Bacillus anthracis

Perhaps no other microorganism has received as much attention for its use as a potential agent for bioterrorism as Bacillus anthracis. In spite of the fact that the organism has been known for a very long time, limited progress has been made in developing a vaccine or understanding its biochemical and genetic properties. The genus Bacillus includes aerobic bacilli forming heatresistant spores. B. anthracis are the only non-motile and the most pathogenic bacilli in this genus. Pulmonary anthrax can be caused by inhalation of just 10,000 spores of anthrax and is fatal unless treated immediately with antibiotics. Anthrax is actually a disease of herbivorous animals with humans getting infected by spores due to accidental entry into the body by contact with infected animals or contaminated animal products, insect bites, inhalation or ingestion. This lethality is principally due to the polysaccharide capsule that helps the bacterium to evade immune attack and the tripartite toxin that can kill the host depending on the mode of entry of the bacillus into the host and the host’s immune status.