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N. Orologas, S.G. Delivopoulos, A. Dimopoulou andI. Tsekos. 2005. Effects of 2,6-dichlorobenzonitrile on plasma membrane cellulose synthesizing complexes and cellulose localization in cells of the red alga Erythrocladia subintegra. Phycologia44: 465–476.The effects of 2,6-dichlorobenzonitrile (DCB), a cellulose biosynthesis inhibitor, on the density (number/μm2), the terminal complex (TC) length, the number of transverse rows of TC subunits of cellulose synthesizing linear TCs, the cellulose microfibril width and the structure and morphology of cell wall and colonies of Erythrocladia subintegrawere investigated. Treatment with 50 μM of DCB caused a partial inhibition of cellulose synthesis, whereas with higher concentrations (75–100 μM) no TCs were observed; this shows that DCB at these concentrations inhibits cellulose synthesis completely. The cellulose synthesis inhibition had a direct impact on the morphology of cells and colonies as well as on the cell wall structure and function. Ultrathin sections of E. subintegrafixed cells, when treated with cellobiohydrolase I (CBH I)–colloidal gold complex (10 nm gold particles), showed significant gold particle labelling on the cellulose microfibrils. In order to better visualize the inhibitory effect of DCB on cellulose synthesis, a combination of DCB and CBH I–gold complex treatment was applied. DCB treatment with increasing concentration (50, 75 and 100 μM) resulted in a gradual decreasing of the enzyme–gold labelling.