Clostridia
Clostridium
The genus Clostridium consists of Gram-positive, mostly obligately anaerobic bacteria capable of forming highly resistant endospores. They are ubiquitously found in soil, aquatic sediments, and the intestinal tracts of humans and animals. While many species play an essential role in decomposing organic matter, some members are known pathogens causing diseases such as tetanus or botulism.
Details
Identification
Rod-shaped morphology, Gram-positive (in young cultures), formation of terminal or subterminal endospores, obligately anaerobic growth.
Social behavior
Often associated in biofilms or as part of the complex microbiota in the gut.
Diet
Chemoorganotrophic; decomposition of carbohydrates (saccharolytic) or proteins (proteolytic) through fermentation.
Overwintering
Survival as highly resistant endospores that withstand extreme temperatures and desiccation.
Ecology
Ecological role
Important decomposers in the carbon cycle; some species fix atmospheric nitrogen (e.g., C. pasteurianum).
Natural predators
Bacteriophages, protozoan organisms (amoebae).
Competitor species
Other anaerobic bacteria, in the gut primarily Bacteroidetes and Firmicutes.
Ecosystem service
Nutrient recycling through the decomposition of cellulose and proteins in anaerobic environments.
Threats
Use of broad-spectrum antibiotics (leading to dysbiosis), oxygen ingress into anaerobic habitats.
Scientific profile
Profile
Habitat
Ubiquitously distributed in anoxic environments: soils, limnic and marine sediments, sewage, manure, and as part of the natural intestinal flora.
Ecological role
Important decomposers in nutrient cycling; degradation of complex organic matter. Some species (e.g., C. pasteurianum) are capable of free-living nitrogen fixation.