There has been an awful lot of noise about SOLiD recently; Ignite buys 100 machines, SOLiD4 and HQ are coming and data is getting published.
For a long time ABI have been playing catch-up to Illumina after almost missing out on next-gen sequencing. I went to Agencourt Personal Genomics in the week after ABI purchased the SOLiD technology and it looked like a good bet back then (late 2006), however it has taken rather longer than AB would have liked to make users really sit up and take notice. AGBT seemed to generate an awfully large number of blogs and tweets (and other stuff I don’t know the terms for) many of which were positive. So I thought about where the battle lines are really going to be drawn and what chance there is of getting to a more competitive market. I have some conflicts to declare, I am an experienced Illumina user and I have never tried to run a SOLiD instrument. Please feel free to correct my inaccuracies and leave your comments.
Library Prep: Illumina have very nice, if currently far too expensive, library prep methods. Most of the people I know have switched to home-brew kits where they get enzymes from companies like Enzymatics and NEB. Some enterprising users are making their own adapters as well but this seems to be a step too far for the majority of users. However the library prep methods are incredibly flexible and allow users to develop their own improvements and applications. Library prep is being automated by companies Genome centres to run 384 library preps, of course they have capacity for this kind of throughput.
ABI have a more complex library prep reliant on emulsion PCR which sounds like it is getting streamlined with their own automation, snappily named EZ-Bead. They also already supply kits which can be run in 96well plate format and users with large sample cohorts need access to this kind of throughput.
To my knowledge neither offer robust normalisation methods which will allow the holy grail of 1:1 mixing of 96 samples in a run.
Read-length: Both generate lots and lots of reads, we are now talking about billions rather than millions. And as you almost certainly know these are what are classed as short read platforms, of course it kind of depends what your reference point is but one PIs 50bp headache is a post-docs heaven. Does this matter in the light of SOAPdenovo anyway?
Where there is a clear difference is in the maximum length each company can achieve. Illumina were doing 100 last year and 150 is probably at Sanger or Broad now. Of course it takes a long time to run this length and the quality on 100bp is not as good as I would like right now with a 2% error rate at 100bp, so not useful for SNP calling for instance. But the attractive bit is the cost of this on a per bp basis. Illumina sequencing gets cheaper and cheaper as read length gets longer.
ABI can only achieve 50bp with a possible maximum of 75bp. As I understand this is a limitation of the chemistry and means we are unlikely to see improvements at the rate of Illumina for instance. Please correct me if I am wrong!
Sequence data: The third big difference, base space vs colour space! Biologists can align sequence reads on their desktops, I even know of one or two people that still print sequences out or align in Word. Sequences mean something to us that colour-space confuses. When I first heard about colour-space it took a few days to sink in but the idea of such high-quality sequence data made the system incredibly attractive when thinking about SNP calling in heterogenous tumours where their is also contaminating stromal tissue. For two to three years I have been waiting for a publication to showcase the increased quality you can achieve on SOLiD vs Illumina, it has not yet arrived. I cannot help but wonder why. ABIs recent adverts keep making the claims about increased accuracy but if it is so much better where is the data? Many centres now have both Illumina and SOLiD so lots of people have done this comparison. Some may also have made purchasing decisions based on it (however I think not, read on to find out why!)
Who wins?
I think it is Illumina but not necessarily for many of the reasons above. Quite simply they got there first* with a product that made an impact on biology that many of us are still grappling to understand. It was a true paradigm shift. The last three years have seen such a change in the kind of questions we can ask of biological systems. For a molecular biotechnologist, which is kind of how I would describe myself, it has been a fun rollercoaster to be on.
I really hope ABI can make a dent in Illumina’s market share of next-gen, and soon. We need better competition but perhaps we can’t afford to take advantage of it? The cost of change for any small or medium institute already invested in Illumina is very high as it is not just instrument depreciation and consumables but sample handling pipelines and bioinformatics analysis that needs to be reworked. Places like mine are unlikely to change.
The dent is probably going to come from groups that are investing now, they have a choice. If they are confident that 75bp is probably going to fit most of their needs (and I suspect it will) then ABI are offering cheaper genomes. This has to be balanced against the risk they eventually run out of cash, or the desire to keep putting more into this side of the business.
Of course both best might be off if Complete Genomics get their business right. I would much rather pay $5k for everything than $3k for reagents and have to do all the work myself!
* It was actually Solexa that got there first and without bridge-amplification on a flowcells they may not have made it. British brains and American muscle wins the day again!