# Escherichia coli Mono-Association Modulates Ionotropic Receptor-Dependent Behaviors in Drosophila melanogaster

## TL;DR

This study shows that Escherichia coli can change how fruit flies behave in response to sensory cues, and these changes depend on specific receptors in the flies' sensory systems.

## Contribution

The study demonstrates that E. coli mono-association modulates sensory-driven behaviors in Drosophila, with effects mediated by ionotropic receptor pathways.

## Key findings

- E. coli mono-association alters phototaxis and mechanosensory responses in Drosophila larvae.
- In adult flies, E. coli increases attraction to fermentation cues and sucrose consumption, effects reduced in IR co-receptor mutants.
- Microbial status influences sensory-driven behaviors through conserved IR pathways in Drosophila.

## Abstract

Insects depend on their sense of smell and taste to find food, mates, and suitable places to reproduce. These behaviors influence ecological interactions and, in some species, contribute to the spread of insect-borne diseases and agricultural losses. Our work shows that microbial status influences insect sensory behaviors and that mono-association with Escherichia coli under controlled conditions alters behavioral outputs in flies. Several of these behavioral effects are reduced or absent in ionotropic receptor (IR) co-receptor mutants, including IR25a and IR76b, suggesting that IR pathways contribute to microbe-dependent behavioral modulation. Our findings further support a role for microbes in shaping insect sensory-driven behaviors. Understanding how bacteria influence insect sensory systems provides insight into host–microbe interactions and establishes a framework for future studies investigating how microbial cues shape insect behavior.

Chemosensory systems are crucial for insect survival, enabling host-seeking, food acquisition, and oviposition site selection. While insect-associated microbes are known to influence host development and immunity, their role in modulating chemosensory behavior remains poorly understood. Here, we show that mono-association with Escherichia coli alters sensory-driven behaviors in both larval and adult axenic Drosophila melanogaster. In larvae, E. coli mono-association altered phototaxis and mechanosensory responses across genotypes, while changes in tunneling and thermosensory behaviors were reduced or absent in ionotropic receptor (IR) co-receptor mutants. In adults, E. coli mono-association increased attraction to fermentation cues (apple cider vinegar, ethanol) and enhanced sucrose consumption in wild-type and Orco-deficient flies, whereas these effects were reduced or absent in IR co-receptor mutants (IR25a− and IR76b−). Together, these findings indicate that under defined gnotobiotic conditions, E. coli exposure alters sensory-driven behavioral outputs relative to axenic controls. Effects are reduced or absent in IR co-receptor mutants, consistent with a role for IR pathways in mediating these behavioral shifts. These findings support a role for microbial cues in shaping insect sensory-driven behaviors and highlight the importance of microbial status in interpreting behavioral phenotypes. This work provides a framework for future studies investigating how microbial signals interact with conserved sensory pathways.