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Using synthetic, DNA-barcoded microbes to track food contamination.

a study from researchers at Harvard Medical School develops and tests a synthetic microbial system capable of determining the origin of objects, with a view to identifying sources of foodborne illnesses. The team states their DNA-barcoded spores are incapable of growing in the wild, are derived from safe microbe strains, and can be sprayed onto goods such as crops or manufactured products to be detected months to years later.

Every year, a staggering 48 million people in the USA alone will suffer from foodborne illnesses, resulting in approximately 128,000 hospitalizations and 3,000 deaths. This public health epidemic is exacerbated by the economic damage running into billions of dollars caused by product recalls, highlighting the need to rapidly and accurately determine the sources of foodborne illnesses. However, due to the ever-increasing elaboration of global supply chains consisting of an almost infinite choice of foodstuffs for consumers, the task of tracking and tracing the exact origin of contaminated items can be fraught with obstacles. Now, a study from researchers at Harvard Medical School develops and tests a synthetic microbial system capable of determining the origin of objects, with a view to identifying sources of foodborne illnesses. The team states their DNA-barcoded spores are incapable of growing in the wild, are derived from safe microbe strains, and can be sprayed onto goods such as crops or manufactured products to be detected months to years later. The study is published in the journal Science.

Previous studies indicate microorganisms are very dependent on the interaction with their environments, meaning microbial colonies in homes, on cell phones, or on human bodies all possess unique compositions, much like a fingerprint. Despite this specificity, attempts to use microbial fingerprints to identify an object, its source, and its historical movements can be time-consuming as well as difficult to scale. This is where the use of synthesized DNA could prove effective for labeling produce if the DNA barcodes manufactured in large volumes prove to be low-cost and remain easily detectable on goods over a long period of time. However, thus far these prerequisites have not been met. The current study develops a DNA-barcoded microbial system with the ability to label objects in an inexpensive, scalable, and reliable manner.

The current study combines artificial spores derived from Saccharomyces cerevisiae, also known as baker’s yeast with Bacillus subtilis, a common and widespread bacterium, designed to be incapable of growing in the wild. Artificial DNA made up of short, biologically inert sequences were then integrated into the genomes of the chimera microbes with the arrays designed to create billions of unique barcodes. Results show an inexpensive tool employing CRISPR, dubbed SHERLOCK, able to detect the presence of a genetic target rapidly, successfully read the DNA barcodes. Data findings involving more than a trillion of the modified spores confirmed they are unable to form colonies through the deletion of salient genes.

The efficacy of the barcoded microbial spore system was evaluated using a variety of experiments to demonstrate durability and ease of use. The lab states when the synthetic microbes were applied to soil, the spores were transferred to and from objects around them, enabling tracking at a meter-scale resolution. They go on to add when the artificial microorganisms were applied to plant leaves, the spores are not readily transferred to surrounding objects indicating the potential to track agricultural products. Amazingly, DNA-barcoded Bacillus subtilis remained detectable on tagged produce even after washing and cooking.

The team surmises they have manufactured a synthetic microbial system incorporating DNA barcodes to track, trace, and source transported goods. For the future, the researchers state they are now working to include programmed cell death and timed location history into the artificial tracking system.

Source: Harvard Medical School

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