[Study of the state of intracellular iron in photosynthesizing purple sulfur bacteria using the Mossbauer effect].

The work presents the results of the first stage of the study on the valent and structural state and function of the iron atoms in the donor-acceptor environment of the photosynthetic reaction centres of purple bacteria. 57Fe was introduced by cultivating the microorganisms in a medium enriched in this isotope. At 77 K the maxima observed in the Mössbauer spectra in intact freeze-dried cells at a speed of +2 mm/s and --1 mm/s are attributed to doublets 1.11 with the isomer ahifts of 1.3 and 0.5 mm/s respectively and the constants of the quadrupole splitting (Q.S.) of 2 mm/s and 2.2 mm/s. These are presumed to arise from cytochromes type c. The Mössbauer parameters of the intense assymetric quadrupole-split doublet of a more complex nature in the mid of the spectrum with line widths of 0.5 to 7.0 mm/s and 0.5 to 1.5 mm/s fit to these of bacterial ferredoxin. From the analysis of the control and dithionite-treated samples of the temperature dependency of the observable parameters over a temperature range of 77 to 300 K it can be concluded that in cells the iron atoms are present in various valency and spin states and the relation between the redox states of the iron atoms is dependent, in particular, on the age of the culture. The Mössbauer spectra of the cell fragments indicate that most of the intracellular iron, first of all the heme iron, is bound to the fraction of photosynthetic membranes.