Non-mammals and mammal gut defense

Contributed by Nguyet Kong

Chitin is a fibrous substance containing polysaccharides and form the exoskeleton of arthropods such as insects and crustaceans and are commonly found on the cell walls of fungi. Non- mammals protect their gut walls with a layer of chitin and that layer will prevent bacterial infections. Whereas a mammal’s gut is lined with a mucous layer that will allow the bacteria to colonize but not invade the cell wall.

Dr. Keisuke Nakashima led his team to map the evolution of the animal gut and have it evolved to defend itself from bacterial infection.  They have noticed that Tunicates (sea squirts) have both chitin and mucous in their guts and are closely related to mammals and is an ideal model to study the evolution of the gut lining. When the team chemically prevent the tunicates to produce chitin they would die unless treated with antibiotics. It shows that the chitin layer has some antimicrobial properties preventing bacterial infection. After years, Dr. Nakashima’s team was able to map out an evolutionary path from one gut model to the next, showing how one body structure is able to keep everyone safe from bacterial infection.


Nakashima, K. et al. Chitin-based barrier immunity and its loss predated mucus-colonization by indigenous gut microbiota. Nature Communications, 2018; 9: 3402.

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