Pushing into a new chapter of technologically advanced biological sensors, scientists from
the University of California San Diego and their colleagues in Australia have
engineered bacteria that can detect the presence of tumor DNA in a live organism.
Their innovation, which detected cancer in the colons of mice, could pave the way to new
biosensors capable of identifying various infections, cancers and other diseases.
The advancement is described in the journal Science. Bacteria previously have been designed
to carry out various diagnostic and therapeutic functions, but lacked the ability to identify
specific DNA sequences and mutations outside of cells. The new “Cellular Assay for Targeted
CRISPR-discriminated Horizontal gene transfer,” or “CATCH,” was designed to do just that.
Tumors are known to disperse, or shed, their DNA into the environments
surrounding them. Many technologies can analyze purified DNA in the lab,
but these cannot detect DNA where it is released. Under the CATCH strategy,
the researchers engineered bacteria using CRISPR technology to test free-floating DNA
sequences on a genomic level and compare those samples with predetermined cancer sequences .
Many bacteria can take up DNA from their environment, a skill known as natural
competence. The researchers collaborated on the idea of natural competence in relation to bacteria
and colorectal cancer, the third-leading cause of cancer-related death in the United States.
They began to formulate the possibility of engineering bacteria, which are already
prevalent in the colon, as new biosensors that could be deployed inside the gut to detect DNA
released from colorectal tumors. The researchers focused on Acinetobacter baylyi, a bacterium in
which they identified the elements necessary for both taking up DNA and using CRISPR to analyze it.
The researchers designed, built and tested Acinetobacter baylyi as a sensor for identifying
DNA from KRAS, a gene that is mutated in many cancers. They programmed the bacterium with
a CRISPR system designed to discriminate mutant from normal (non-mutated) copies
of KRAS. This means that only bacteria that had taken up mutant forms of KRAS, as found
in precancerous polyps and cancers, for example, would survive to signal or respond to the disease.
The new research is based on previous ideas related to horizontal gene transfer,
a technique used by organisms to move genetic material between one another in a manner distinct
from traditional parent-to-offspring genetic inheritance. While horizontal
gene transfer is widely known from bacteria to bacteria, the researchers achieved their goal
of applying this concept from mammalian tumors and human cells into bacteria.
The researchers are now adapting their bacteria biosensor strategy with new circuits and
different types of bacteria for detecting and treating human cancers and infections.
In the future, disease will be treated and prevented by cells,
not pills. A living bacterium that can detect DNA in the gut is a tremendous opportunity
to act as a sentinel to seek and destroy gastrointestinal, and many other, cancers.
While the new invention requires further development and refinement,
the synthetic biology team at UC San Diego continues to optimize the advanced biosensor
strategy. Pickpockets are rampant in just about every community and the microscopic world is no
different because wherever and whenever there's something of value there's a skilled Thief ready
to make the snatch but who's the top thief in town meet the bacterium a cinetobacter balei
abelia is notorious for finding and stealing DNA from its environment through a Nifty skill called
natural competence this allows for horizontal Gene transfer so that a bale I can integrate cell-free
DNA into its own genome to produce new proteins to help it grow and survive but could we perhaps
employ this skill set for good for instance could a Bailey eye be coerced into finding
and stealing mutated DNA from cancer that's what our International research team sought to find out
we engineered a bale I to find and steal DNA specifically the mutated Keras Gene which helps
colorectal cancer grow we term this new bioassay catch to collect and characterize cell-free DNA
if a bale I found any tumor DNA it would then turn on a linked antibiotic resistance Gene
this tells us that the catch was successful and that cancerous tissue was found but what does this
mean for the real world this technique of Life detecting life shows how engineered bacteria can
be designed to detect specific DNA sequences to diagnose and even treat disease in hard to reach
places like but not limited to the colon indeed even Rogue Pig Pockets deserve a second chance