Jack Guynn, president and chief executive of the

Federal Reserve's

Atlanta branch, will retire Oct. 1, marking the latest in a series of membership changes for the central bank's policymaking committee.

Guynn is part of the

Federal Open Market Committee

, the group that has the power to raise or lower short-term interest rates.

He's also the second FOMC member in the last two days to say he's leaving. On Wednesday, Mark Olson submitted his resignation from the Fed's board of governors to become chairman of the Public Company Accounting Oversight Board.

"It has been a privilege to spend my entire career working with the Federal Reserve Bank of Atlanta, including the last 10 years as the bank's president," Guynn said. "The Atlanta Fed is an outstanding organization, and its employees are truly dedicated to helping ensure the health and stability of the nation's economy and financial system. I am proud of the work that we have accomplished together, and I feel the bank is well positioned for the future."

Guynn, who turns 64 later this year, will focus on community and civic work and other interests, according to a statement on the Atlanta Fed's Web site. The statement also said Guynn's retirement will give him time to recover from surgeries he's had because of arthritis. He has spent 42 years with the Atlanta Fed.

David Ratcliffe, chairman of the Atlanta Fed's board of directors, will form a committee to conduct a nationwide search for candidates to fill Guynn's position. Ratcliffe is the chairman, president and chief executive of

Southern Co.

(SO) - Get Report

.

No timetable has been set, but if a replacement isn't found by the day Guynn retires, Patrick Barron, the Atlanta Fed's first vice president, will assume the duties of the president on an interim basis. The Atlanta Fed oversees Alabama, Florida, Georgia, and parts of Louisiana, Mississippi and Tennessee.

Meanwhile, Olson, a member of the board of governors since December 2001, was named this week by

Securities and Exchange Commission

Chairman Christopher Cox to head the Public Company Accounting Oversight Board until 2010.

The PCAOB was created through the Sarbanes-Oxley Act to oversee the audits of public companies and to protect the interests of investors.

Olson won't attend the June 28-29 meeting of the FOMC. "Mark's leadership and wide experience in financial services and government were invaluable assets for the effective operation of both the board and Federal Reserve System during his tenure," said Fed Chairman Ben Bernanke in a statement. "He has been an exemplary colleague, and I will miss his wise counsel."

The Fed's board of governors has seven members. They are nominated by the U.S. President and must be confirmed by the Senate. A full term is 14 years.

Earlier this year, Randy Kroszner and Kevin Warsh filled two vacant seats on the board of governors, and Roger Ferguson, the Fed's vice chairman, stepped down after more than eight years on the board. Of course, the biggest change at the Fed came in February when Bernanke took over for Alan Greenspan, who had led the central bank since 1987.