Reaction centres (RC) from the purpie bacterium Rhodohacter sphaeroides (strain R-24.1 and carotenoid-free mutant R-26.1) were separated and immobilized in isotropic and stretched polyvinyl alcohol (PVA) films. Absorption, fluorescence, delayed luminescence (8-300 K) and photoacoustic spectra (PAS) of immobilized samples were measured. The RC from wild strain R-24.1 and ffom carotenoid-free mutant R-26.1 were differently oriented in the stretched polymer film. In R-24.1 the long axis of the RC complex was directed under some angle with respect to the perpendicular direction to the PVA film plane, whereas in R-26.1 it was almost perpendicular to this plane. The shapes of linear dichroism (LD) of both strains were different. Delayed luminescence (DL) bands were located in a similar wavelength range as the bacteriochlorophyll and bacteriopheophytin prompt fluorescence bands. Intensity of DL was independent of temperature in the 8-300 K range. The intensity of DL was about three time lower than that of the fluorescence. The dependence of PAS on the frequency of radiation modulation and on the phase shift between modulated acting radiation and measured PAS showed that part of the thermal deactivation was undergoing slowly. Intensity ratio of the slow component to the fast one and/or decay time of the slow component of thermal deactivation were different for various chromophores and for RC ffom the two strains of bacteria.
The photosynthetic bacteria (Rhodospirillum rubrum, Synechococcus and Anabaena variabilis) as well as their fragments embedded in isotropic and anisotropic polymer film were investigated. The orientation of photosynthetic pigments inside these organisms was compared, on the basis of the polarised absorption and fluorescence spectra, with the macroscopic orientation of investigated objects seen under microscope. The anisotropy of fluorescence was much higher than anisotropy of absorption. It showed strong influence of the photoselection by polarised radiation on the various bacterial chromophores exhibiting different orientations in the cells and various yields of fluorescence. The dimensions of cells were investigated on the basis of their photographs and by the scattering of the monochromatic radiation. and A. Planner ... [et al.].