What is Oxford Nanopore Technology (ONT) sequencing?

• In 2015, the first Oxford Nanopore Technology (ONT) sequencing device was released – an entirely new way to sequence DNA. 
• Unlike previous techniques, which were based on DNA replication, ONT doesn’t use any DNA polymerases. Instead, it’s based on a small barrel-shaped protein in a membrane, called a nanopore, and measures changes to electrical current. 
• It was used in 2015 during an Ebola outbreak to help with genomic surveillance.

What is Oxford Nanopore Technology?

• Oxford Nanopore Technology (ONT) is a type of third generation sequencing technology. 
• Unlike all previous sequencing technologies, ONT doesn’t use any DNA polymerases. 
• Instead, it uses a barrel-shaped protein called α-hemolysin – naturally found as a ‘pore’ in a cell membrane, regulating which molecules can enter or leave a cell. This is called a nanopore. 
• α-hemolysin has a diameter of 1 nanometre – just big enough to allow a single strand of DNA through. 

How does ONT work?

• In ONT, the α-hemolysin nanopore is embedded into an artificial membrane inside a sequencing chamber. When a current is applied to the membrane, the DNA travels through the nanopore. 
• As the DNA travels through the nanopore, it obstructs the current flowing across the membrane. 
• The four bases of the DNA (A, T, C and G) are of different shape and size, so cause variations in the current. 
• These variations are measured by an electronic chip. An algorithm converts the data into a sequence which can then be read. 

What are the benefits of Oxford Nanopore Technology (ONT)?

• Despite having a lower accuracy than other technologies, ONT has several unique advantages. 
• It can generate ultra-long reads (up to several millions of base pairs) making it much easier to sequence an entire genome. 
• The instrument is very small – depending on the model, between the size of a phone and a microwave. Comparatively, Illumina and PacBio sequencers are closer in size to fridge-freezers. ONT’s small size makes the technology more accessible outside of the traditional laboratory setting, requiring only a laptop to run it. 
• For example, the smallest ONT sequencer has been used onboard the International Space Station. It has also been used in low-income countries, including during the Ebola pandemic in 2015 – when it read the genomes of Ebola viruses from 14 patients in just 48 hours.