This causes the capsule to swell, and this can be easily visualised by suspension in India Ink. The ink particles cannot penetrate the capsule, which this appears as a halo around the bacterial cells. These resist a range of hazardous environments, and protect against heat, radiation, and desiccation. All these bacteria are 'anaerobic'. The aerobic sporing bacteria can also cause disease.
Anthrax is caused by Bacillus anthracis .
Bacillus cereus causes two types of food poisoning. Some bacteria have an absolute requirement for oxygen. These are the obligate aerobes . Others, the facultative anaerobes can survive in the absence as well as the presence of oxygen. The obligate anaerobes are killed by traces of oxygen.