The effects of 2,6-dichlorobenzonitrile
(DCB, a known inhibitor of cellulose synthesis) and Tinopal LPW
(TPL, an agent which disrupts glucan crystallization) on the structure
of cellulose synthesizing complexes (terminal complexes, TCs)
in the xantho-phycean alga Vaucheria hamata were investigated.
DCB (1OI~M) inhibits nascent fibril formation from the TC subunit
(based on the absence of impressions) although it does not alter
the overall shape of the rectangular TC during the short treatment
of 20 min. With a prolonged treatment (60 min), the arrangement
of TC subunits becomes disordered, and particles generally exhibited
as doublets of subunits are released from each other. DCB also
interferes with the formation of the overall shape of the TC although
it does not disturb the conversion into TC rows of the subunits
(the zymogenic precursor of the TC) packed in the globules. A
15 min treatment with TPL (1 mM) destroys the TC integrity by
reducing the subunits into small fragments or particulate aggregates.
The particulate rows of the TC are interrupted at many points,
and fragments and particulate aggregates are dispersed by prolonged
treatment (45 min) with TPL. Unlike DCB, TPL inhibits the conversion
of globule subunits into TC rows. New insights on the structural
characteristics necessary for cellulose microfibril assembly and
possible mechanisms for the biogenesis of the Vaucheria
TC come from these data.