DISTRIBUTION OF BACTERIOCHLOROPHYLL HOMOLOGS IN NATURAL-POPULATIONS OF BROWN-COLORED PHOTOTROPHIC SULFUR BACTERIA

The relative content of the four main bacteriochlorophyll (BChl) e hom ologs of several populations of brown-colored photosynthetic sulfur ba cteria grown in different waterbodies have been measured by high perfo rmance liquid chromatography and statistically compared by principal c omponent analysis. All the studied populations possessed representativ e pigment patterns enriched in highly alkylated bacteriochlorophyll e homologs, with average contents of 0.02 +/- 0.01%, 24.92 +/- 1.01%, 35 .2 +/- 0.70%, and 39.9 +/- 0.71% for bacteriochlorophyll e(1), e(2), e (3), and e(4), respectively. These values clearly differ from those ob tained for the same species growing under optimal conditions in labora tory batch cultures (4.99 +/- 1.11%, 50.34 +/- 1.73%, 28.99 +/- 0.63%, and 15.6 +/- 1.10% for bacteriochlorophyll e(1), e(2), e(3), and e(4) , respectively). Multivariate statistical analyses grouped samples int o two main clusters, both related to the developmental state of the po pulation. Within these clusters, samples were arranged in several grou ps according to the physiological pigment response of bacterial popula tions to light limitation. Although bacteriochlorophyll homolog distri bution cannot be considered a real taxonomic character, the data prese nted demonstrate that it can be useful in field studies since it refle cts both the physiological status of the cells and the light regime un der which the population has been growing.