Cellulose digestion by subterranean and drywood termites is dependent upon which organism?

Cellulose digestion in subterranean and drywood termites is primarily facilitated by protozoa that reside in the termite's digestive system. These protozoa have a symbiotic relationship with the termites, allowing them to break down the cellulose found in wood and plant material, which the termites consume as their primary food source.

The protozoa possess specialized enzymes that can degrade cellulose into simpler sugars, which the termites can then absorb and utilize for energy. This unique digestive process allows termites to thrive on a diet that would otherwise be indigestible to many other organisms. Without these protozoa, termites would struggle to extract the necessary nutrients from their cellulose-rich diet.

While bacteria can also play a role in the digestive process of some termites, the key players in cellulose digestion for both subterranean and drywood termites are the protozoa. Other organisms such as fungi and viruses do not have the same primary role in this specific digestion process, hence they are not the correct focus in this context.