This study demonstrates that the termite flagellate Trichomitopsis termopsidis possesses intrinsic cellulolytic activity independent of bacterial symbiosis. Researchers cultivated T. termopsidis axenically (without bacteria) and showed that homogenates of these flagellates enzymatically hydrolyzed carboxymethylcellulose, producing reducing sugars with peak activity at pH 5.3 and 37°C. The cellulolytic activity was substantially higher than in the related flagellate Tritrichomonas foetus. In vivo experiments involved defaunating termites (Zootermopsis species) and refaunating them with either axenic T. termopsidis, heat-killed flagellates, or mixed intestinal fauna. After one year, 46% of termites refaunated with living T. termopsidis survived, compared to 0% of those receiving heat-killed flagellates. These results establish that T. termopsidis itself digests cellulose and provides essential nutrition to termites, resolving earlier questions about whether bacterial endosymbionts were responsible for cellulolytic activity. The findings confirm the nutritional importance of this flagellate in the termite-protist symbiosis.

Key findings

• Axenically-cultivated T. termopsidis possesses significant cellulolytic activity (3450 U/mg protein) independent of bacterial symbionts
• Homogenates of T. termopsidis hydrolyzed carboxymethylcellulose optimally at pH 5.3 and 37°C
• Defaunated termites refaunated with live T. termopsidis showed 46% survival after one year, versus 0% survival with heat-killed flagellates
• T. termopsidis can support termite nutrition and prolong survival when present as the sole cellulolytic flagellate