Scientific revision note: This version uses precise terminology, avoids unsupported claims, distinguishes established facts from experimental applications, and adds evidence-based limitations and references.
Why sequencing platforms evolved
The Human Genome Project showed that genome-scale sequencing was possible, but it also revealed that older sequencing approaches were too slow and expensive for routine biological and clinical use. The central goal of platform development has been to increase throughput, reduce cost per base, improve accuracy, shorten turnaround time, and match sequencing output to biological questions.
Illumina sequencing-by-synthesis
Illumina technology is based on sequencing by synthesis using reversible terminator chemistry. Libraries are attached to a flow cell and amplified into clusters. During each sequencing cycle, fluorescently labeled nucleotides are incorporated, imaged, chemically unblocked, and extended in the next cycle. Illumina became dominant because it combines high throughput, high short-read accuracy, mature instruments, and strong ecosystem support.
Its major limitation is read length. Short reads are excellent for many applications, including small-variant detection, RNA-seq, ChIP-seq, targeted panels, and microbial sequencing, but they are less powerful for repetitive regions, structural variants, haplotype phasing, and complete de novo assembly without additional information.
Historical NGS platforms
Roche/454 sequencing used pyrosequencing and produced longer reads than early short-read platforms, but it suffered from homopolymer errors and high cost. SOLiD sequencing used sequencing by ligation and color-space encoding; it achieved high accuracy but required complex analysis and eventually declined in use. Ion Torrent eliminated optical imaging by detecting pH changes caused by nucleotide incorporation, but homopolymer length estimation remained a challenge.
Long-read sequencing
Long-read sequencing platforms were developed to solve problems that short reads cannot easily resolve. Pacific Biosciences single-molecule real-time sequencing detects fluorescent signals during DNA synthesis in zero-mode waveguides. Oxford Nanopore sequencing measures changes in ionic current as DNA or RNA passes through nanopores. Long reads are valuable for de novo genome assembly, structural variants, repeat expansion, transcript isoforms, methylation analysis, and haplotype phasing.
Choosing the correct platform
Platform choice should be based on the biological question rather than brand popularity. Short reads are usually cost-effective for variant calling, expression profiling, targeted panels, and high-throughput population studies. Long reads are preferable when continuity, structural information, phasing, or direct molecule-level information is essential. Many modern studies combine short and long reads to benefit from both accuracy and contiguity.
Key scientific takeaway
Sequencing platforms are tools with different strengths. The best platform is the one that matches the sample type, genome complexity, target variant class, required accuracy, budget, and downstream analysis plan.
Sequencing platform comparison
| Platform/technology | Signal or chemistry | Best suited for | Main limitation |
| Illumina SBS | Fluorescent reversible terminator incorporation | High-throughput short-read sequencing | Read length and repeat resolution |
| Roche/454 | Light signal from pyrosequencing | Historical longer early NGS reads | Cost and homopolymer errors |
| SOLiD | Ligation and color-space encoding | Historical high-accuracy short reads | Complex workflow and analysis |
| Ion Torrent | Semiconductor pH detection | Targeted sequencing and rapid workflows | Homopolymer signal interpretation |
| PacBio SMRT | Single-molecule real-time fluorescence | Long-read assemblies and consensus accuracy | Input, cost, and data requirements |
| Oxford Nanopore | Nanopore ionic-current signal | Ultra-long reads, portability, direct RNA/DNA | Raw error profile and analysis calibration |
References
- Margulies, M., et al. (2005). Genome sequencing in microfabricated high-density picolitre reactors. Nature, 437, 376-380.
- Bentley, D. R., et al. (2008). Accurate whole human genome sequencing using reversible terminator chemistry. Nature, 456, 53-59.
- Rothberg, J. M., et al. (2011). An integrated semiconductor device enabling non-optical genome sequencing. Nature, 475, 348-352.
- Goodwin, S., McPherson, J. D., & McCombie, W. R. (2016). Coming of age: Ten years of next-generation sequencing technologies. Nature Reviews Genetics, 17, 333-351.
- Logsdon, G. A., Vollger, M. R., & Eichler, E. E. (2020). Long-read human genome sequencing and its applications. Nature Reviews Genetics, 21, 597-614.