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Updated: Jun 17, 2025
Systemic Bacterial Infection and Immune Defense Phenotypes in Drosophila Melanogaster
Published on: May 13, 2015
High sugar diets can increase susceptibility to bacterial infection in Drosophila melanogaster
Andrea M Darby1,2, Destiny O Okoro1,2, Sophia Aredas2,3,4
1Department of Entomology, Cornell University, Ithaca, New York, United States of America.
Abstract:
Overnutrition with dietary sugar can worsen infection outcomes in diverse organisms including insects and humans, through generally unknown mechanisms. In the present study, we show that adult Drosophila melanogaster fed high-sugar diets became more susceptible to infection by the Gram-negative bacteria Providencia rettgeri and Serratia marcescens. We found that P. rettgeri and S. marcescens proliferate more rapidly in D. melanogaster fed a high-sugar diet, resulting in increased probability of host death. D. melanogaster become hyperglycemic on the high-sugar diet, and we find evidence that the extra carbon availability may promote S. marcescens growth within the host. However, we found no evidence that increased carbon availability directly supports greater P. rettgeri growth. D. melanogaster on both diets fully induce transcription of antimicrobial peptide (AMP) genes in response to infection, but D. melanogaster provided with high-sugar diets show reduced production of AMP protein. Thus, overnutrition with dietary sugar may impair host immunity at the level of AMP translation. Our results demonstrate that dietary sugar can shape infection dynamics by impacting both host and pathogen, depending on the nutritional requirements of the pathogen and by altering the physiological capacity of the host to sustain an immune response.
Insights
High sugar diets increase fruit fly susceptibility to bacterial infections by impairing immune defenses. This study reveals how sugar overnutrition impacts host immunity and pathogen growth, affecting infection outcomes.
Area of Science:
- Immunology
- Microbiology
- Nutritional Science
Background:
- Overnutrition, particularly high dietary sugar intake, is linked to worsened infection outcomes in various organisms, including humans.
- The precise mechanisms by which dietary sugar affects host susceptibility and infection dynamics remain largely unknown.
Purpose of the Study:
- To investigate the impact of high-sugar diets on host susceptibility to bacterial infections in Drosophila melanogaster.
- To elucidate the mechanisms underlying sugar-induced changes in infection outcomes, focusing on host immunity and pathogen proliferation.
Main Methods:
- Adult Drosophila melanogaster were fed either standard or high-sugar diets.
- Infection susceptibility was assessed using Gram-negative bacteria (Providencia rettgeri and Serratia marcescens).
- Bacterial proliferation, host hyperglycemia, and antimicrobial peptide (AMP) gene expression and protein production were analyzed.
Main Results:
- Drosophila melanogaster on high-sugar diets exhibited increased susceptibility to P. rettgeri and S. marcescens infections.
- Bacterial proliferation was enhanced in flies fed high-sugar diets, correlating with increased host mortality.
- While AMP gene transcription was induced, AMP protein production was reduced in flies on high-sugar diets, suggesting impaired translation.
Conclusions:
- Dietary sugar overnutrition can compromise host immunity by impairing antimicrobial peptide translation, independent of gene expression.
- High-sugar diets can alter infection dynamics by affecting both host immune capacity and pathogen growth, depending on pathogen nutritional needs.
- These findings highlight the critical role of dietary sugar in modulating host-pathogen interactions and infection severity.
