• 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.

Source:TH