Remembrance of things past—bacterial memory of gut inflammation

Engineered bacteria not exposed to inflammatory signals do not turn on the memory circuit thereby remain colorless. from the presence of the inflammatory chemical tetrathionate, the memory circuit switches on as well as colors the engineered bacteria blue. Credit: Wyss Institute as well as Harvard Medical School.

The microbiome, or the collections of microorganisms present from the body, is actually known to affect human health as well as disease as well as researchers are thinking about completely new ways to use them as next-generation diagnostics as well as therapeutics. Today bacteria through the normal microbiome are already being used in their modified or attenuated form in probiotics as well as cancer therapy. Scientists exploit the microorganisms’ natural ability to sense as well as respond to environmental- as well as disease-related stimuli as well as the ease of engineering completely new functions into them. This particular is actually particularly beneficial in chronic inflammatory diseases like inflammatory bowel disease (IBD) that will remain difficult to monitor non-invasively. However, there are several challenges associated with developing living diagnostics as well as therapeutics including generating robust sensors that will do not crash as well as are capable of long-term monitoring of biomolecules.


In order to use bacteria of the microbiome as biomarker sensors, their genome needs to be modified with synthetic genetic circuits, or a set of genes that will work together to achieve a sensory or response function. Some of these genetic alterations may weaken or break normal signaling circuits as well as be toxic to these bacteria. Even in cases where the probiotic microbes tolerate the modifications, the engineered cells can have growth delays as well as be outcompeted by various other components of the microbiome. As a result, probiotic bacteria as well as engineered therapeutic microbes are rapidly cleared through the body, which makes them inadequate for long period monitoring as well as modulation of the organism’s tissue environment.

A team at the Wyss Institute of Biologically Inspired Engineering led by Pamela Silver, Ph.D., designed a powerful bacterial sensor having a stable gene circuit in a colonizing bacterial strain that will can record gut inflammation for six months in mice. This particular study offers a solution to previous challenges associated with living diagnostics as well as may bring them closer to use in human patients. The findings are reported in Nature Biotechnology.

Silver, who is actually a Core Faculty member at the Wyss Institute as well as also the Elliot T. as well as Onie H. Adams Professor of Biochemistry as well as Systems Biology at Harvard Medical School, thought of the gut as a first application due to This particular system due to its inaccessibility by non-invasive means as well as its susceptibility to inflammation in patients suffering through chronic diseases like IBD. “We think about the gut as a black box where the idea is actually hard to see, however we can use bacteria to illuminate these dark places. There is actually great interest through patients as well as doctors that will push us to build sensors for biomarkers of gut conditions like IBD as well as colon cancer,” said Silver, “We believe that will our work opens up enormous possibilities that will can exploit the flexibility as well as modularity of our diagnostic tool as well as expand the use of engineered organisms to a wide variety of applications.”

Key to the team’s work is actually the introduction of a memory module to the circuit that will is actually able to detect a molecule of interest as well as respond to This particular exposure long after the stimulus is actually gone. As bacteria can be rapidly cleared through the intestinal tract, the team used a strain of bacteria that will is actually part of the microbiome of mice, as well as engineered the idea to contain the sensory as well as memory elements capable of detecting tetrathionate. Tetrathionate is actually a transient metabolic molecule produced from the inflamed mouse intestine as a result of either infection with pathogenic bacteria like Salmonella typhimurium as well as Yersinia enterocolitica or genetic defects affecting inflammation.

The synthetic genetic circuit designed by the Wyss team contains a “trigger element” that will is actually adopted through the natural system specifically recognizing the biomarker (in This particular case tetrathionate) in cells, or that will can be developed using synthetic approaches when no prior sensor exists. The second element from the circuit is actually the “memory element” that will resembles a toggle switch as well as has been adapted through a virus that will attacks bacteria. the idea consists of two genes (A as well as B for simplicity) that will regulate each various other depending on whether the stimulus is actually present. from the tetrathionate sensor, the product of gene A blocks expression of gene B when tetrathionate is actually absent. When tetrathionate is actually produced during inflammation as well as is actually sensed by the trigger element, levels of A decrease as well as the gene B is actually induced as well as begins to shut off expression of gene A. The expression of the B gene is actually also coupled to a reporter gene which turns bacteria through colorless to blue only when they have switched the memory element on. The switch can be maintained from the on state long after the first tetrathionate exposure.

After verifying the functionality of the sensor in a liquid culture of bacteria, David Riglar, Ph.D., the study’s first author, was able to show that will the idea detected tetrathionate in a mouse product of gut inflammation caused by infection with S. typhimurium up to six months after administration of the sensor-containing probiotic bacteria. Through simple analysis of fecal matter, the synthetic circuit’s memory state was confirmed to be on as well as its DNA unchanged as well as stable. “Our approach is actually to use the bacteria’s sensing ability to monitor the environment in unhealthy tissue or organs. By adding gene circuits that will retain memory, we envision giving humans probiotics that will record disease progression by a simple as well as non-invasive fecal test,” said Riglar.

Silver’s team plans to extend This particular work to sensing inflammation from the human gut as well as also to develop completely new sensors detecting signs of a variety of various other conditions.

“Pam’s work demonstrates the power of synthetic biology for advancing medicine as the idea provides a way to rationally as well as rapidly design sophisticated sensors for virtually any molecule. If successful in humans, their technology would certainly offer a much less expensive as well as more specific way to monitor gut function at home than sophisticated imaging instruments used today”, said Donald Ingber, M.D., Ph.D., Founding Director of the Wyss Institute, the Judah Folkman Professor of Vascular Biology at Harvard Medical School as well as the Vascular Biology Program at Boston Children’s Hospital, as well as Professor of Bioengineering at the Harvard John A. Paulson School of Engineering as well as Applied Sciences.


Explore further:
Synthetic biologists engineer inflammation-sensing gut bacteria

More information:
Engineered bacteria can function from the mammalian gut long-term as live diagnostics of inflammation, Nature Biotechnology (2017). nature.com/articles/doi:10.1038/nbt.3879

Journal reference:
Nature Biotechnology

Provided by:
Harvard University

Remembrance of things past—bacterial memory of gut inflammation

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