U-M microbiologist Philip C. Hanna, Ph.D., announced his research findings in a Feb. 14 presentation at the American Association for the Advancement of Science meeting. His results are surprising, because most scientists believe B. anthracis spores will not germinate and grow unless they are inside a living host.
During the AAAS symposium on how environmental organisms cause disease, Hanna described what happened when he seeded soil samples with anthrax spores, added water and let the mixture incubate in the laboratory.
"All stages of the anthrax life cycle were found to occur in soil, including germination of spores, bacterial reproduction and formation of new spores," said Hanna, an assistant professor of microbiology and immunology in the U-M Medical School. "Our research demonstrates that anthrax can complete its full life cycle without a mammalian host."
Researchers in Hanna's laboratory collected ordinary soil from the bank of Miller's Creek part of the Huron River watershed in Ann Arbor, Mich. The soil was taken to the laboratory where U-M researchers added water and dormant spores of an attenuated, or non-infectious, strain of B. anthracis, which was modified to make it safe to handle in university laboratory facilities. Then, U-M scientists cultured the soil samples to see whether the spores would germinate and grow.
"The spores germinated and continued to replicate until they ran out of nutrients in the soil," Hanna reported. "At that point, the bacteria formed new spores and became dormant. In every case, we ended up with more spores than we added t
Contact: Sally Pobojewski
University of Michigan Health System