Where a bustling laboratory would have unmasked the genetic secrets of tortilla chips and cereal, the room is quiet. The refrigerator is bare. And the patrons who stream through the Massachusetts Museum of Contemporary Art are informed that one of its planned exhibits has been seized by the FBI.The tale began last month in Buffalo with a frantic call to 911 when artist Steven Kurtz’s 45-year-old wife died of cardiac arrest in her sleep. The paramedics who responded were alarmed by Kurtz’s laboratory, where he kept a machine for analyzing the genetic makeup of food, along with various strains of bacteria.Kurtz’s work was confiscated. The exhibit he and his colleagues had prepared for MASS MoCA was canceled. And at least eight other artists have been called before a federal grand jury. Supporters who have created a defense fund for Kurtz say they believe he is being investigated for possession of biological agents.