Biodegradation of Bacillus anthracis endospores in compost

Abstract

Anthrax, a lethal infectious disease affecting primarily herbivores, is caused by an endospore-forming bacterium, Bacillus anthracis (BA). Endospores from BA are extremely stable in the environment and pose a communicable risk as a natural zoonosis and as a potential bioweapon. Composting results in microbial biodegradation of organic matter, reaching temperatures up to 70°C. I investigated the ability of compost to inactivate BA. Surrogate strains were sporulated over a range of temperatures to mimic natural sporulation environmental variations and tested in two separate experiments. The first, exposed four surrogate strains to temperatures mimicking a previous long-term (150 days) field-scale compost temperature profile. The second, composted BA endospores from two surrogate strains in laboratory scale composters for 33 days. Composting resulted in a 2 and 4 log10 reduction in endospore viability in oven and lab scale experiments, respectively. Results suggest composting has potential as a disposal method for anthrax related mortalities.