HETEROTROPHIC GROWTH OF 2 STRAINS OF THE ACIDO-THERMOPHILIC RED ALGA GALDIERIA-SULPHURARIA

The acido- and thermophilic red alga Galdieria sulphuraria (Galdieri) Merola grows under mixo- and heterotrophic conditions on 27 different sugars and sugar alcohols as sole carbon source. We separated two stra ins from an isolate originally collected at Mt. Lawu (Indonesia). Thes e strains are indistinguishable in growth and pigmentation under autot rophic conditions. However, under heterotrophic conditions, strain 074 W lost most of its pigments whereas strain 074 G stayed green on all substrates tested. Strain 074 G had the highest pigment content when g rown on sugar alcohols. Usually the alga exhibited a short lag-phase f ollowed by logarithmic growth. However, when transferred from auto- to heterotrophic conditions a lag-period of about 45 days was observed w ith the sugar alcohol dulcitol. Similarly, long lag-periods were also noticed for strain 074 G grown on D-mannitol and for strain 074 W grow n on D-ribose. The length of the lag-phase is a function of the length of the previous culture under autotrophic conditions. This enormous v ersatility in the heterotrophic growth of Galdieria sulphuraria presen ts an ideal system to study the metabolism of rare sugars and sugar al cohols.