Whole cells, chlorosome-membrane complexes and isolated chlorosomes of the green mesophilic filamentous bacterium
Oscillochloris trichoides, representing a new family of the green bacteria
Oscillochloridaceae, were studied by optical spectroscopy and electron microscopy. It was shown that the main light-harvesting pigment in the
chlorosome is BChl
c. The presence of BChl
a in chlorosomes was visualized only by pigment extraction and fluorescence spectroscopy at 77 K. The molar ratio BChl
c: BChl
a in chlorosomes was found to vary from 70:1 to 110:1 depending on light intensity used for cell growth. Micrographs of negatively
and positively stained chlorosomes as well as of ultrathin sections of the cells were obtained and used for morphometric measurements
of chlorosomes. Our results indicated that
Osc. trichoides chlorosomes resemble, in part, those from
Chlorobiaceae species, namely, in some spectral features of their absorption, fluorescence, CD spectra, pigment content as well as the
morphometric characteristics. Additionally, it was shown that similar to
Chlorobiaceae species, the light-harvesting chlorosome antenna of
Osc. trichoides exhibited a highly redox-dependent BChl
c fluorescence. At the same time, the membrane B805–860 BChl
a antenna of
Osc. trichoides is close to the membrane B808–866 BChl
a antenna of
Chloroflexaceae species.
This revised version was published online in June 2006 with corrections to the Cover Date.
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