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Introduction to Ion Torrent Semi-conductive Sequencing Technology

Ion Torrent™ (Thermo Fisher Scientific) is based on a technology that directly translates chemically encoded information (A, C, G, T) into digital information on a semiconductor chip, resulting in simpler, faster, and more cost-effective sequencing. Compared with other sequencing technologies, cost per run is lower.


How Ion Torrent Semi-conductive Sequencing Technology Works?

During the DNA polymerase reaction nucleotides will be incorporated into the growing DNA strand. Each nucleotide incorporation results in release of a hydrogen ion as a by product. The number of free hydrogen ions influences the pH in the reaction chamber and the pH can be measured by conductivity changes with a pH-meter. If more than one nucleotide is incorporated by the polymerase the pH will increase proportional to the number of incorporated nucleotides and intensify the signal.
In order to reach sufficient signal strength individual DNA fragments are coupled to beads followed by clonal DNA amplification prior sequencing. Each bead is sequenced in a single reaction chamber (well) on a chip with millions of reaction wells. The chip will sequentially be flooded with solutions containing the different nucleotides (A, C, G, T). A signal only arises if the analogue nucleotide is incorporated in the growing DNA strand.
The corresponding signals in conductivity changes will be monitored and analyzed for each reaction well separate, leading to the sequence information of each individual DNA fragment coupled to a single bead.
The following video demonstrates how the Ion Torrent™ technology works in more detail.


Ion Torrent Sequencing Time, Read Length and Throughput

Ion Torrent offers different kits for sequencing of 200 or 400 nucleotide long reads. The Ion Proton system only enables 200 nucleotide read length whereas the Ion PGM series enable sequencing of 400 nucleotide long reads.
The sequencing time is about three to six hours, depending on the desired read length and the used system. The hands on time can be reduced by utilization of the Ion Chef system during library and template preparation.
For the PGM system different chips are available (314, 316 and 318) the number of reads per run with these chips varies between 0.5 and 5.5 million reads. The Ion Proton™ system offers one chip that enables 60-80 million reads per sequencing run.


Ion Torrent Sequencing Platforms and its ApplicationsIonPGM

Ion Torrent™ provides different sequencing machines, the Ion PGM, the Ion Proton and the lately introduced Ion S5™ and Ion S5™ XL systems.
The Ion S5™ and Ion S5™ XL systems are especially developed for targeted sequencing were less data output is needed. Major application will be infectious disease research, human inheritability screening and cancer screening.IonProtonThe Ion PGM will be suitable for targeted amplification similar as the Ion S5™ and Ion S5™ XL systems. Furthermore, the PGM can be applied for more complex microbial sequencing including whole genome sequencing of bacteria and viruses.
The Ion Proton system can be applied for sequencing projects that need larger data output such as exome sequencing or transcriptome sequencing.
For more information about the different systems and its applications visit the Thermo Fisher website.