Cellulose accumulation and a cellulose synthase gene are responsible for cell aggregation in the cyanobacterium Thermosynechococcus vulcanus RKN. Plant Cell Physiol

A thermophilic cyanobacterium, Thermosynechococcus vulcanus RKN, exhibits cell aggregation under low tempera-ture illuminated conditions as a means of physiological ac-climation to avoid excess light stress. The cell aggregation was dispersed with cellulase treatment. We developed a method to quantify small amounts of cellulose by partial cellulose purification followed by quantitation of liberated glucose by cellulase. Under low temperature illuminated light conditions, cellulose accumulation was induced approximately 2-fold, to 10 mg (4 109 cells)1, and slightly preceded aggregation. Based on sequence similarity, three candidate genes for cellulose synthase (Tvtll0007, Tvtlr1795 and Tvtlr1930-33) were cloned from T. vulcanus. Gene dis-ruption analysis showed that only Tvtll0007 was responsible for both the light- and low temperature-induced cell aggre-gation and the induction of cellulose accumulation. Gene expression analysis suggested that the low temperature illu-minated conditions quickly induced expression of Tvtlr1795 and Tvtlr1930-33, while the induction of Tvtll0007 was slow. These results suggest that Tvtll0007 encodes a functional cellulose synthase whose activity may not be regulated at the transcriptional level