The brain is thought to be a sterile environment, free from germs. But unexpected deposits of bacteria have been found inside brain tumors, apparently affecting how the cancers grow and behave, a new study says. "This work opens a new dimension in our understanding of brain tumor biology," senior researcher Dr. Jennifer Wargo , a professor of surgical oncology and genomic medicine at the University of Texas MD Anderson Cancer Center in Houston, said in a news release. "By mapping how microbial