Drosophila Antimicrobial Peptides and Lysozymes Regulate Gut Microbiota Composition and Abundance

Abstract

This study advances current knowledge in the field of host-microbe interactions by demonstrating that the two families of immune effectors, antimicrobial peptides and lysozymes, actively regulate the gut microbiota composition and abundance. Consequences of the loss of these antimicrobial peptides and lysozymes are exacerbated during aging, and their loss contributes to increased microbiota abundance and shifted composition in old flies.

Antimicrobial Peptides—or How Our Ancestors Learned to Control the Microbiome

“…Previous studies had shown that in animals in which the Relish transcription factor, the major regulator of the immune deficiency (IMD) pathway, which includes hundreds of genes involved in systemic and local immunity, was deleted, animals died prematurely with increased numbers of gut bacteria, and the species composition of the gut bacteria was different. In this report, Marra et al ( 8 ) focus on the role of the two major antimicrobial effectors expressed in the gut, AMPs and lysozyme, in the management of gut microbiota. Marra et al ( 8 ) created germfree flies by sterilization at the embryonic stage.…”

“…In this report, Marra et al ( 8 ) focus on the role of the two major antimicrobial effectors expressed in the gut, AMPs and lysozyme, in the management of gut microbiota. Marra et al ( 8 ) created germfree flies by sterilization at the embryonic stage. Two days after reaching adulthood, the flies were provided food containing specific microbial inocula.…”

“…Marra et al ( 8 ) demonstrated that the AMP mutants resembled the Relish mutants with respect to microbial load and composition, suggesting that much of the disturbance of the gut microbiome observed in IMD mutants can be ascribed to impaired expression of AMPs. Furthermore, flies lacking AMPs or lysozymes displayed reduced microbial community stability and high degree of variability of microbial species.…”

“…Loss of these effector molecules led to increased microbiota abundance and changes in composition as the flies aged. Thus, the work by Marra et al ( 8 ) demonstrates that both AMPs and lysozymes play a role in establishing and maintaining a stable gut microbiome in Drosophila . Marra and colleagues’ innovation is to show that AMPs not only defend the fly from systemic infection but also, with the assistance of lysozyme, help shape the microbiome of its gut.…”

The Interplay between the Host Microbiome and Pathogenic Viral Infections

“…Importantly, the interplay between the microbiome and viral infections depends on the microbiome’s species composition and diversity. This microbial composition is dynamic, changing over time depending on multiple factors: the host species ( 5 ) and developmental stage ( 6 ), aging ( 7 , 8 ), the particular organ within the host ( 9 , 10 ), the host immunity ( 11 – 13 ), diet ( 14 , 15 ), geography ( 8 , 16 ), infections with other pathogens ( 17 , 18 ), the host metabolic signaling pathways ( 19 ), or even circadian rhythms ( 20 ). The microbe’s composition can also be altered due to microbial transfers between humans, other animals, and the environment ( 21 ).…”