Research progress on protists in termite guts

The hindgut of termites is enlarged and specialized, providing a habitat for intestinal microorganisms. Except for termites belonging to the Termitidae family, all other termite species harbor protists in their guts. The protists in the termite gut belong to the Parabasalia phylum and Preaxostyla phylum Oxymonadida order. The gut protists of termites coexist with various bacteria, exhibiting a coevolutionary relationship. Termites, protists, and bacteria form a triplex symbiotic system. The distribution of gut protists within the intestine demonstrates heterogeneity. The transmission mechanism of gut protists not only ensures the stability of the gut microbiota but also facilitates the continuous evolution of the gut microbiota colonies in termites. Additionally, the abundance of gut protists in termites is influenced by various factors, including termite caste and diet. Gut protists are crucial for termites as they contribute to the decomposition of lignocellulose, nitrogen fixation, participation in intestinal gas metabolism, and the provision of nutrients to termites. This article provides a comprehensive review of the classification of gut protists, symbiotic bacteria of protists, spatial distribution, transmission, and functions of protists, aiming to offer a valuable reference for future research.