An engineered bacterial symbiont allows noninvasive biosensing of the honey bee gut environment

Abstract

The honey bee is a powerful model system to probe host–gut microbiota interactions, and an important pollinator species for natural ecosystems and for agriculture. While bacterial biosensors can provide critical insight into the complex interplay occurring between a host and its associated microbiota, the lack of methods to noninvasively sample the gut content, and the limited genetic tools to engineer symbionts, have so far hindered their development in honey bees. Here, we built a versatile molecular tool kit to genetically modify symbionts and reported for the first time in the honey bee a technique to sample their feces. We reprogrammed the native bee gut bacterium Snodgrassella alvi as a biosensor for IPTG, with engineered cells that stably colonize the gut of honey bees and report exposure to the molecules in a dose-dependent manner through the expression of a fluorescent protein. We showed that fluorescence readout can be measured in the gut tissues or noninvasively in the feces. These tools and techniques will enable rapid building of engineered bacteria to answer fundamental questions in host–gut microbiota research.

Engineering Gut Symbionts: A Way to Promote Bee Growth?

“…Although the majority of studies on engineered S. alvi have involved increasing the survival rate of bees via stimulation of their immune responses towards pathogens or parasites, the use of gut symbionts as biosensors of the intestinal environment has recently been explored. In a recent work, S. alvi was engineered to detect the concentrations of IPTG and indicate these as fluorescent protein expression that can be detected in gut tissues or feces [31]. This is a prototypic biosensor that could be adapted to any environmental factor in a dose-dependent manner.…”

“…Other dominant symbionts, e.g., Se. marcescens N10A28 [31] and B. apis [32], have also been engineered and investigated thoroughly for compatible genetic parts and expression [32]. All reported works and conditions are summarized in Table 1.…”

“…Successful observation of bacterial colonization and developed bee microbiome toolkit (BTK) used for genetic engineering based on CRISPR system [32] Biosensor development for gut environment S. alvi Successful development of a biosensor system for fluorescence readouts through gut tissue and feces [31] Pathogen or parasite resistance…”