Unexpected capacity for organic carbon assimilation by Thermosynechococcus elongatus, a crucial photosynthetic model organism

Abstract

Genetic modification of key residues of photosystems is essential to identify functionally crucial processes by spectroscopic and crystallographic investigation; the required protein stability favours use of thermophilic species. The currently unique thermophilic photosynthetic model organism is the cyanobacterial genus Thermosynechococcus. We report the ability of Thermosynechococcus elongatus to assimilate organic carbon, specifically d-fructose. Growth in the presence of a photosynthesis inhibitor opens the door towards crucial amino acid substitutions in photosystems by the rescue of otherwise lethal mutations. Yet depression of batch-culture growth after 7 days implies that additional developments are needed. Surprisingly, Thermosynechococcus is capable of organic carbon assimilation. The most efficient organic carbon source is d-fructose at levels around 40 mm. A step towards genetic modification of key photosystem II residues in T. elongatus.