Putrefaction, i.e.
fermentation of proteins, is considered the final step following death, and is carried out mainly by
anaerobic organisms from the bowel. Putrefying bacteria produce a plethora of
enzymes which aid in disintegration of the body. Because of the lack of immune function within the body, these bacteria spread through blood vessels and utilize the carbohydrates and proteins in the blood as an energy source. The main bacterial species carrying out putrefaction is
Cl. welchii. This bacterium contributes to gas formation, breakdown of remaining blood clots, disintegration of tissue, and marked hemolysis. This breakdown begins immediately after death, but is not noticeable to the naked eye until several hours after death. Within the following days, the body will begin to break down. The three characteristics of putrefaction are discoloration, disfiguration, and dissolution. There are many factors that could affect the rate of putrefaction in animals such as age, body composition, temperature, and if the body is located in a wet or dry area. Temperature must be between 0 °C and 48 °C for putrefaction to occur. The established bacterial community also play a role in rate of putrefaction. Newborn children that have not been fed will decompose slower than a toddler's body because of the lack of an established gut microbiota. Older individuals tend to decompose slower than younger individuals. Individuals with inflammatory disease, eating disorders, sepsis, and other conditions that affect gut microbiota will all decompose at different rates. ==Putrefying bacteria in gut==