Regulators on Friday shut down Ohio’s AmTrust Bank, the fourth-largest bank to fail this year. They also closed five others, bringing to 130 the number of U.S. banks to be brought down so far in 2009 by recession and mountains of bad debt. The Federal Deposit Insurance Corp. took over AmTrust Bank, based in Cleveland, with about $12 billion in assets and $8 billion in deposits. Its failure is expected to cost the federal deposit insurance fund an estimated $2 billion. Also seized by the FDIC were three Georgia banks, Benchmark Bank, based in Aurora, Ill., and Greater Atlantic Bank of Reston, Va.