Clostridium sp. (tetanus, gangrene, botulism) is different from Bacillus sp. (anthrax, food poisoning, etc.). Clostridium is strictly anaerobic (loves low or no-oxygen environments such as cans or infected wounds), while Bacillus can live under both conditions. Both clostridia and bacilli are spore-formers when environmental conditions aren't favorable for them, though clostridial spores aren't as narly as hardy as those of bacilli.
Tetanus (Clostridium tetani) causes disease by excreting a toxin which bonds to nerve end-plates, causing severe spasms - similar but not quite the same as that which nerve agents do. Clostridium botulinum is the reason for the canning industry, and his cousin Clostridium perfringens is the reason for the autoclave (basically a smaller version of the pressure-steam can heater). These diseases are generally treated with anti-sera or anti-toxins.
Anthrax (Bacillus anthracis) causes disease by direct infection, and these bacteria grow so fast that they choke the host's cells with their waste products. Bacilli are so wimpy with regards to antibiotics that some are used to test food products for the presence of antibiotics.
But... when the Anthrax scare was going around, I was carrying some of this stuff in my pocket ;-)
