Studies of the iron-sulphur centers of the bacteriaShewanella putrefaciens (MR-1)

Shewanella putrefaciens (MR-1) can be grown using any one of several different terminal acceptors. This respiratory versatility stimulated our studies of the respiratory chain of MR-1 using whole cell analysis by ESR spectroscopy. Initial analyses of aerobically grown cells showed the presence of the succinate dehydrogenase complex. Also, it was shown that inS. putrefaciens which were grown anaerobically with iron as the only electron acceptor the ESR signal atg=2.021 appeared at low temperatures. This ESR signal resembled the ESR signal of Fe-S] center of succinate dehydrogenase in oxidized state. However this new ESR signal had a different temperature dependence. It can be seen at temperature as high as 40 K. The line shape andg-factor of the new center are very similar to those of 3Fe-4S] centers. As this ESR signal can be seen only in the anaerobic samples grown with iron as acceptor we suggest that this center is located in the terminal part of the respiratory chain and is associated with the reduction of iron or another electron acceptor.