Putrefying bacteria are bacteria involved in putrefaction of living matter. Along with other decomposers, they play a critical role in recycling nitrogen from dead organisms.
Nitrogen cycle
Putrefying bacteria use amino acids or urea as an energy source to decompose dead organisms. In the process, they produce ammonium ions. Nitrifying bacteria then convert this ammonium into nitrate, which can then be used by plants to create more proteins thus completing the nitrogen cycle.
References
Putrefying bacteria Wikipedia(Text) CC BY-SA