Bacteria reprogrammed to study bee microbiota

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A reprogrammed bacterium is able to colonize the bee’s intestine and fluor
A reprogrammed bacterium is able to colonize the bee’s intestine and fluoresce when it detects a molecule of interest (a molecule called IPTG in this case). Audam Chhun, DMF-UNIL

Scientists at the University of Lausanne have succeeded in reprogramming a bacterium that can now detect a specific molecule in a bee’s intestine and produce a fluorescent protein in response, which can be observed under a microscope.

The microorganisms present in the intestine, known as the gut microbiota, play a key role in our development and health. Understanding the interactions between these microorganisms and their hosts is not easy, as the intestinal environment is complex and, above all, difficult to access. Studying it non-invasively to detect and measure the myriad of molecular information it contains remains a real challenge.

A team of researchers co-led by Yolanda Schaerli and her colleague Philipp Engel , both associate professors in the Department of Fundamental Microbiology (DMF) at the University of Lausanne’s Faculty of Biology and Medicine, have overcome this problem by genetically reprogramming bacteria naturally present in the gut to act as in situ biosensors.

A simple but precious microbiota

Compared to the intestinal microbiota of humans, which is highly complex in terms of diversity, that of the honeybee is relatively simple, comprising only a few bacterial species. It is nonetheless vital to the health of the bee, making it a promising model system for studying the interactions between the gut microbiota and its host. Philipp Engel warns: "Although the bee is an essential pollinator for natural ecosystems and agriculture, its population has been declining dramatically for several years, due in particular to an increase in the number of viruses and parasites, and the unreasonable use of pesticides. It is therefore vital to learn more about the complex interactions between hosts and microbiota.

Bacterial biosensors could have proved a great help in this task, but the lack of methods for non-invasively sampling the contents of bees’ intestines, as well as the limited genetic tools available for modifying gut bacteria, have so far been a hindrance to their development.

Stable colonization of the gut

In a study published in the March 5, 2024 issue of the journal PLOS Biology, scientists from Lausanne have built a versatile molecular toolbox for genetically modifying bee symbionts, within the framework of the NCCR Microbiomes . For the first time, they have developed a technique for sampling bee feces. We genetically reprogrammed a bacterium native to the bee’s gut, Snodgrassella alvi, to make it a biosensor for a synthetic sugar derivative (IPTG)", explains Yolanda Schaerli, co-director of the study. The bees were then fed these modified bacteria in the laboratory. We observed that these bacteria were capable of stably colonizing the intestine. They were found in the faeces of colonized individuals. The presence of IPTG added to the bees’ food is signalled via the expression of a fluorescent protein that can be observed under the microscope", reports DrSc. Audam Chhun, postdoctoral fellow in Pre Schaerli’s team and first author of the paper. The fluorescence reading can be measured not only non-invasively in faeces, but also directly in intestinal tissue.

Answering further questions

This proof of principle demonstrates the potential of genetically reprogramming bee gut bacteria as diagnostic tools. These could, in the future, be potentially modified to detect other signals, such as pesticides, viruses and parasites, and thus help answer fundamental questions in research into host microbiota and bee health", concludes Yolanda Schaerli.