The doubling time of the fastest-growing bacterium, Clostridium perfringens, is 6.3 minutes under exceptional laboratory conditions. This generation time was recorded in thioglycollate medium at about 43°C, making it a reported record rather than a rate the bacterium maintains everywhere.
Clostridium perfringens is a Gram-positive, anaerobic, rod-shaped, spore-forming bacterium. Its ability to multiply rapidly is especially important in warm, oxygen-poor foods such as meat and poultry. The organism can form durable endospores that survive unfavorable conditions and then germinate when conditions improve.
The 6.3-minute figure comes from experiments on particular strains and media. In ground beef and at other temperatures, measured generation times can be longer. This is why food-safety guidance emphasizes rapid cooling and correct hot-holding of cooked foods. C. perfringens is also associated with food poisoning and serious wound infections, including gas gangrene.