Cm. Borrego et al., Temporal variability of Chlorobium phaeobacteroides antenna pigments in a meromictic karstic lake, AQUAT MIC E, 17(2), 1999, pp. 121-129
The changes in the antenna pigment composition of Chlorobium phaeobacteroid
es growing in 2 meromictic basins of Lake Banyoles have been studied during
a seasonal growth period. Changes involved both the increase in carotenoid
content and the enrichment of the antenna in highly alkylated bacteriochlo
rophyll e (BChl e) homologs. Interestingly, the homolog composition at the
end of the growth period was similar to those measured in laboratory cultur
es incubated at low Light intensity, which are characterised by high amount
s of BChl e homologs possessing larger alkyl substituents at the C-8 positi
on of the macrocycle (i.e, isobutyl and neopentyl). Furthermore, difference
s in the vertical distribution of both pigments were also observed. Seasona
l variation in the antenna pigment composition could be interpreted as a re
sponse to gradual changes in light regime during growth, mainly caused by s
elf-shading and by the development of an overlying population of the purple
sulphur bacterium Chromatium minus, which acts as a biological filter for
Light. The increase in both antenna pigments is discussed on the basis of r
ecent findings on the spectral properties of BChl e and carotenoids and the
role in the light adaptation processes is accordingly interpreted.