CELLULOSE MICROFIBRIL ASSEMBLY IN ERYTHROCLADIA-SUBINTEGRA ROSENV - AN IDEAL SYSTEM FOR UNDERSTANDING THE RELATIONSHIP BETWEEN SYNTHESIZINGCOMPLEXES (TCS) AND MICROFIBRIL CRYSTALLIZATION

The marine red alga Erythrocladia subintegra synthesizes cellulose mic rofibrils as determined by CBH I-gold labelling, X-ray and electron di ffraction analyses. The cellulose microfibrils are quite thin, ribbon- like structures, 1-1.5nm in thickness (constant), and 10-33 nm in widt h (variable). Several laterally associated minicrystal components cont ribute to the variation in microfibrillar width. Electron diffraction analysis suggested a uniplanar orientation of the microfibrils with th eir (101) lattice planes parallel to the plasma membrane surface of th e cell. The linear particle arrays bound in the plasma membrane and as sociated with microfibril impressions recently demonstrated in Erythro cladia have been shown in this study to be the cellulose-synthesizing terminal complexes (TCs). The TCs appear to be organized by a repetiti on of transverse rows consisting of four TC subunits, rather than by f our rows of longitudinally-arranged TC subunits. The number of transve rse rows varied between 8-26, corresponding with variation in the leng th of the TCs and the width of the microfibrils. The spacings between the neighboring transverse rows are almost constant being 10.5-11.5 nm . Based on the knowledge that Acetobacter, Vaucheria, and Erythrocladi a synthesize similar thin, ribbon-like cellulose microfibrils, the str uctural characteristics common to the organization of distinctive TCs occurring in these three organisms has been discussed, so that the mod e of cellulose microfibril assembly patterns may be deciphered.