Advances in DNA sequencing technology are occurring at an incredible speed and Kevin Hopkins is one of the Museum’s Next Generation Sequencing Specialists working with the sequencing technologies used at the Museum to produce relevant data for our Microverse research.
“The challenge is being able to bring together the technology, often developed in biomedical settings, and the samples at the Museum, where limited and often damaged DNA from specimens is the only chance we have of sequencing them. My job involves designing methods that work for our unusual samples, extracting DNA and producing sequencing ready samples from it, and running our MiSeq and NextSeq next generation sequencing platforms.”
What is DNA sequencing?
DNA sequencing is the process of reading the order of nucleotide bases (adenine, guanine, cytosine and thymine) in a particular strand of DNA. Sequencing can be used for many different applications, such as defining a specific gene or a whole genome. The best way to sequence DNA is in sections; this is because there are a number of challenges to sampling the whole genome of a species in one go.
There is so much data within a genome that it takes an incredibly long time for any sequencing machine to process the information. In the Microverse project we are analysing short strands of DNA. At least 60 samples are loaded into the sequencer at a time and the analysis takes a total of 65 hours. If we were to analyse the whole genome rather than smaller parts, it would take a considerably greater amount of time, but luckily we don’t need to do it for The Microverse project.
Another challenge for sequencing can be old DNA that has been degraded into very short sections, in this situation it is difficult to gain enough DNA from all the microorganism in the samples, to study the community composition. To avoid this in The Microverse project, we asked the schools to return the biofilm samples in a DNA preservative to minimise the degradation of the DNA.
When Kevin receives the samples from Anne, the lead researcher on the project, he performs two quality control checks before loading them into the DNA sequencer: these are the concentration of the samples and the average DNA strand length. It is important to know both of these factors as they allow us to estimate the number of DNA fragments that are in each sample.
The equipment that Kevin uses to sequence DNA is an Illumina MiSeq which can sequence up to 75,000 samples per year. Having equipment like this allows scientists at the Museum to carry out research such as looking at plant DNA to reveal the history of their evolution in relation to climate change, and using molecular work to benefit human health by understanding tropical diseases such as leishmaniasis, as well as exploring microbial diversity in soil, lakes and oceans.
During DNA sequencing the DNA double helix comprising two strands of DNA is split to give single stranded DNA. This DNA is then placed into a sequencing machine alongside chemicals that cause the free nucleotides to bind to the single stranded DNA. Within this sequencing cycle when a nucleotide, which is fluorescently charged, successfully binds to its complementary nucleotide in the DNA strand (A with T and vice versa, G with C and vice versa), a fluorescent signal is emitted. The intensity and length of this fluorescent signal determines which nucleotide base is present, and is recorded by the sequencing machine. The sequencer can read millions of strands at the same time.
Why is this important?
DNA sequencing is vitally important because it allows scientists to distinguish one species from another and determine how different organisms are related to each other. In the Microverse project we are using the sequencer to identify the taxonomic groups of the microorganisms in the samples that you have sent to the Museum.
Katy Potts is one of the trainees on the Identification Trainers for the Future programme, who is based at the Angela Marmont Centre for UK Biodiversity. Alongside her work on the Microverse project she is developing her skills in insect identification, particularly Coleoptera (beetles).
If you are taking part in the Microverse project the deadline for sending us your samples is Fri 29 May.