Bacterial muropeptides promote OXPHOS and suppress mitochondrial stress in mammals

Mitochondria as sensors of intracellular pathogens

Mitochondria must sense their environment to enable cells and organisms to adapt to diverse environments and survive during stress. However, during microbial infection, an evolutionary pressure since the inception of the eukaryotic cell, these organelles are traditionally viewed as targets for microbes. In this opinion we consider the perspective that mitochondria are domesticated microbes that sense and guard their 'host' cell against pathogens. We explore potential mechanisms by which mitochondria detect intracellular pathogens and induce mitochondria-autonomous responses that activate cellular defenses.

Bacterial peptidoglycan acts as a digestive signal mediating host adaptation to diverse food resources in C. elegans

Food availability and usage is a major adaptive force for the successful survival of animals in nature, yet little is known about the specific signals that activate the host digestive system to allow for the consumption of varied foods. Here, by using a food digestion system in C. elegans, we discover that bacterial peptidoglycan (PGN) is a unique food signal that activates animals to digest inedible food. We identified that a glycosylated protein, Bacterial Colonization Factor-1 (BCF-1), in the gut interacts with bacterial PGN, leading to the inhibition of the mitochondrial unfolded protein response (UPRmt) by regulating the release of Neuropeptide-Like Protein (NLP-3). Interestingly, activating UPRmt was found to hinder food digestion, which depends on the innate immune p38 MAPK/PMK-1 pathway. Conversely, inhibiting PMK-1 was able to alleviate digestion defects in bcf-1 mutants. Furthermore, we demonstrate that animals with digestion defects experience reduced natural adaptation capabilities. This study reveals that PGN-BCF-1 interaction acts as "good-food signal" to promote food digestion and animal growth, which facilitates adaptation of the host animals by increasing ability to consume a wide range of foods in their natural environment.