This 1983 study investigated how calcofluor white, a fluorescent brightener, affects chitin fibril assembly in two fungal species: Saccharomyces cerevisiae and Candida albicans. Researchers used calcofluor as a specific marker for chitin, observing its fluorescence at budding scars, cross-walls, and hyphal tips. When cells were incubated with calcofluor, chitin synthesis proceeded normally, but abnormal deposition of chitin occurred and the crystalline lattice structure failed to form properly. Using protoplasts of C. albicans allowed researchers to examine fibril formation without interference from pre-existing cell walls. Electron microscopy revealed that in the presence of calcofluor, individual chitin fibrils remained dispersed rather than assembling into organized ribbon-like structures. The authors conclude that calcofluor blocks the self-assembly mechanism of chitin microfibrils, likely by competing for hydrogen-bonding sites on nascent polymer chains, preventing their crystallization into the normal organized lattice structure while leaving the enzymatic synthesis intact.

Key findings

• Calcofluor white specifically binds to chitin and serves as an effective fluorescent marker for localizing chitin deposition in yeast cells at budding scars and cross-walls
• Calcofluor treatment does not inhibit chitin synthesis but prevents the crystalline lattice formation, causing abnormal chitin deposition patterns
• In C. albicans protoplasts, calcofluor-treated cells show dispersed individual fibrils and aggregates with low crystallinity instead of the organized ribbon-like microfibril networks seen in control cells
• The data support a self-assembly mechanism for chitin microfibril formation involving hydrogen bonding of polymer chains, which is disrupted by calcofluor competition for these bonding sites