The Krystal hamburger chain has filed for Chapter 11 bankruptcy. The company said it owes between 50 million and 100 million dollars to food suppliers, equipment companies and others and has about 15 million dollars in assets. Founded in Chattanooga, Tennessee, in 1932, Krystal is best known for little, square hamburgers served with steamed buns and chopped onions and late-night service across the Southeast. The company has about 300 restaurants in 10 states. The company previously closed more than 40 restaurants, including 13 that shut down in December. Krystal said shifting consumer tastes, growing costs, tight labor markets and the growth of online food ordering have all contributed to the company’s financial problems.