Clostridia

The Clostridia are a class of Firmicutes, including Clostridium and other similar genera.

Clostridia
File:Clostridium botulinum.jpg
Clostridium botulinum
Scientific classification
Unrecognized taxon (fix):	Clostridia
Orders
Clostridiales Caldicoprobacteraceae Catabacteriaceae Christensenellaceae Clostridiaceae Defluviitaleaceae Eubacteriaceae Gracilibacteraceae Heliobacteriaceae Hungateiclostridiaceae Lachnospiraceae Oscillospiraceae Peptococcaceae Peptostreptococcaceae Proteinivoraceae Ruminococcaceae Symbiobacteriaceae Syntrophomonadaceae Vallitaleaceae Halanaerobiales Halanaerobiaceae Halobacteroidaceae Natranaerobiales Natranaerobiaceae Thermoanaerobacteriales Thermoanaerobacteraceae Thermodesulfobiaceae "Ca. Borkfalkiales" "Ca. Borkfalkiaceae"

The Clostridia are obligate anaerobes. They lack aerobic respiration, and oxygen is toxic to them. Species of the genus Clostridium are all Gram-positive and can form spores.

Studies show they are not a monophyletic group. In fact, they are highly polyphyletic. Their relationships are not certain. Most are put in the Clostridiales, but is not a natural group. It is likely to be redefined in the future.

Most species of the genus Clostridium are saprophytic organisms found in many places, most notably the soil. However, the genus does contain some human pathogens. The toxins produced by some members of the Clostridium genus are among the most dangerous known. Examples are tetanus toxin (known as tetanospasmin) produced by C. tetani and botulinum toxin produced by C. botulinum.

Notable species of this class include:

• Clostridium perfringens (Gangrene, food poisoning)
• Clostridium difficile (Pseudomembranous colitis)
• Clostridium tetani (Tetanus)
• Clostridium botulinum (Botulism)
• Clostridium acetobutylicum
• Clostridium haemolyticum
• Clostridium novyi
• Clostridium oedematiens

Heliobacteria are also members of the class Clostridia.