[A comparative study of the fluorescence properties of the chlorosomal antenna of the green bacterium from the family Oscillochloridaceae and the members from two other families of green bacteria].

The fluorescence properties of bacteriochlorophylls (BChl) of the chlorosomal light-harvesting antenna of Oscillochloris trichoides (strain DG-6) from a new family of green filamentous bacteria Oscillochloridaceae were investigated in comparison with green bacteria from two other families. A strong dependence of the fluorescence intensity of chlorosomal bacteriochlorophyll c of Osc. trichoides on the redox potential of medium was found, which previously was observed only in green sulfur bacteria. The presence of BChl a in chlorosomes did not appear in their absorption spectra but was visualized by fluorescence spectroscopy at 77 K. From the comparative analysis of fluorescence spectral data for the chlorosomal light-harvesting antenna of Osc. trichoides and similar spectral data for green bacteria from two other families, it was concluded that, in some fluorescence spectral features (spectral position of bacteriochlorophyll c/a fluorescence bands; shape and full width at half maximum fluorescence band of chlorosomal bacteriochlorophyll c; the Stokes shift value of bacteriochlorophyll c band; a high molar ratio of bacteriochlorophyll c : bacteriochlorophyll a in chlorosomes that makes the bacteriochlorophyll a fluorescence band unresolved at room temperature; and highly redox-dependent fluorescence intensity of chlorosomal bacteriochlorophyll c), Osc. trichoides chlorosomes are close to the chlorosomal antenna of Chlorobiaceae species.