BIOMASS COMPOSITION AND METHODS FOR THE DETERMINATION OF METABOLIC RESERVE POLYMERS IN PHOTOTROPHIC SULFUR BACTERIA

To study nutrient fluxes within aquatic ecosystems, the synthesis of b iomass and of various storage polymers has been analysed in samples fr om a meromictic alpine lake. Methods are described for the quantitativ e determination of whole cell biomass, glycogen, polyhydroxyalkanoates (PHA) and sulfur. Methods were adapted to conditions present in natur al environments and tested with samples from blooms of Chromatiaceae a nd with corresponding laboratory cultures. Dried bacterioplankton-biom ass has been analyzed for sulfur, glycogen and polyhydroxyalkanoates, and after complete oxidation for SO42-, NO3- and HPO42-. The average e lemental composition of biomass from phototrophic sulfur bacteria, dep leted of sulfur and carbon storage compounds, was C380H580O153N67P3S2. 5 M, where M stands for the content of the remaining minor elements. C , H, O, N, P and S accounted for 86.7% of the total dry mass. Storage sulfur in natural populations was equivalent to 2.5% to 13.5% of the d ry mass; its content varied by 80% within a diurnal cycle. Glycogen co ntents fluctuated by approximately 50%; they accounted for 7.5% to 15. 2% of the dry cell mass. The total content of reserve materials per ce ll never exceeded 30% of the dry mass. PHA had not been found in appre ciable amounts in cells harvested from the natural lake habitat. Under certain conditions in the laboratory Chromatium okenii could be induc ed, however, to produce polyhydroxyalkanoates. Sulfur, glycogen and PH A contents of 33, 26 and 11%, respectively, were achieved under labora tory-culture conditions. Cells with up to 60% of their dry mass consis ting of reserve materials can be obtained under selected laboratory co nditions.