Rhodopseudomonas capsulata differences

Stevens, P., Vertonghen, C., Vos, P. and Ley, J. (1984). The effect of temperature and light intensity on hydrogen gas production by different Rhodopseudomonas capsulata strains. Biotechnol. Lett. 6, 277-282. 

Recently it was found that similar subunit forms could be obtained from the core antenna of both Rhodobacter sphaeroides and Rhodopseudomonas capsulata []. The B820 subunit form thus seems to be a basic form present in at least three different core antennae. This emphasizes the importance of elucidating the specific conformation of this subunit. We used low temperature fluorescence polarization measurements in combination with other spectroscopic techniques (OD and CD) to obtain information on the specific organization of the bacteriochlorophyll pigments in the subunit forms. 

In photosynthetic purple bacteria Rhodopseudomonas capsulata and sphaeroides it has been shown that the carotenoids consist of two spectrally but not chemically different pools (1,2). In vesicle preparations of these bacteria, carotenoid absorbance changes can be induced by illumination. It is generally believed that the mechanism of the carotenoid bandshift has an electrochromic character (3). 

In conclusion, the facts that temperature variations, long incubations at 36 C or reactions with small membrane penetrating molecules, affect both carotenoid populations simultaneously and to the same extent, while enz)miatic digestions with different types of proteinases and with phospholipase A2 affect the two populations differentially, the field-sensitive carotenoids being the most sensitive ones, seem to indicate that in chromatophores of Rhodopseudomonas capsulata and sphaeroides the field-sensitive carotenoids are located closer to the surface than the field-insensitive pool. 

In order to investigate whether the described spectroscopic changes were restricted to the LH Bchl of R.rubrum, we set out to study the oxidation of this Bchl in other Rhodospirillaceae. The results obtained with different Rhodopseudomonas strains are described here. They show, first that chemical oxidation of LH Bchl from Rps,sphaevoides and capsulata induces the formation of a radical which exhibits an ESR signal (3.6 G) and a NIR absorption band (.1235 nm) similar to Rds.rubrum LH Bchl, and second, that such a radical is probably due exclusively to the B870 Bchl. These results indicate that the structure of the B870 complexes of different Rhodospirillaceae has some common features. 

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