Correct Answer: A
Explanation:
Researchers from Columbia University Medical Centre (CUMC) in US have converted natural bacterial immune system into the world's smallest data recorder.
The researchers modified an ordinary laboratory strain of ubiquitous human gut microbe (bacteria) Escherichia coli (E Coli) which enabled it to record their interactions with environment and also time-stamp events.
Such bacteria, swallowed by a patient, might be able to record the changes they experience through the whole digestive tract, yielding an unprecedented view of previously inaccessible phenomena.
Other applications could include environmental sensing and basic studies in ecology and microbiology, where bacteria could monitor otherwise invisible changes without disrupting their surroundings.
CRISPR-Cas, an immune system is found in many species of bacteria.
CRISPR-Cas copies snippets of DNA from invading viruses so that subsequent generations of bacteria can repel these pathogens more effectively.
As a result, the CRISPR locus of the bacterial genome accumulates a chronological record of the bacterial viruses that it and its ancestors have survived.
When those same viruses try to infect again, the CRISPR-Cas system can recognise and eliminate them.
To build their microscopic recorder, the researchers modified a piece of DNA called a plasmid, giving it the ability to create more copies of itself in the bacterial cell in response to an external signal.