Serotonin modulates insect gut bacterial community homeostasis

Area of Science:

• Microbiology
• Neuroscience
• Genetics

Background:

• Metazoan guts host complex microbial communities, but host mechanisms for managing microbial dynamics and maintaining homeostasis are poorly understood.
• Understanding host-microbe interactions is crucial for metazoan health.

Purpose of the Study:

• To investigate the role of serotonin (5-hydroxytryptamine, 5-HT) in regulating gut microbiome homeostasis.
• To elucidate the molecular mechanisms by which 5-HT influences gut microbial composition.

Main Methods:

• Investigated the effect of modulating serotonin synthesis on gut microbiome composition in Bactrocera dorsalis and Aedes aegypti.
• Utilized gene knockdown of phenylalanine hydroxylase (TPH), a 5-HT biosynthetic gene, and measured dual oxidase (Duox) gene expression and reactive oxygen species (ROS) activity.
• Analyzed changes in bacterial community composition, focusing on specific genera like Serratia and Providencia.

Main Results:

• Knockdown of TPH led to increased Duox expression and ROS activity, resulting in a reduced gut microbiome load.
• TPH knockdown decreased the relative abundance of Serratia and Providencia, including opportunistic pathogens.
• Supplementation with 5-hydroxytryptophan, a 5-HT precursor, fully restored the normal gut microbiome phenotype.

Conclusions:

• Serotonin (5-HT) plays a significant role in maintaining gut homeostasis by regulating Duox gene expression and influencing the gut microbiome.
• These findings provide novel insights into the intricate relationship between host neurochemistry and microbial communities in metazoans.