Endospore producing organisms
1. Bacillus - most are soil, freshwater or marine saprophytes and a few are pathogens (ie B. anthracis, the causal agent of anthrax)
2. Clostridium - most are soil or aquatic saprophytes or inhabitants of human intestines, but 4 pathogens are fairly well known - C. tetani (tetanus), C. botulinum (botulism), C. perfringens (gas gangrene), and C. difficile (pseudo-membranous colitis).