DNA by Ciro Santilli 40 Updated 2025-07-16
Since DNA is the centerpiece of life, Ciro Santilli is extremely excited about DNA-related technologies, see also: molecular biology technologies.
As you would expect, not much secret here, we just dumped a 1 liter glass bottle with a rope attached around the neck in a few different locations of the river, and pulled it out with the rope.
And, in the name of science, we even wore gloves to not contaminate the samples!
Figure 1.
Swans swimming in the river when during sample collection
. Source. Swam poo bacteria?
Figure 2.
Tying rope to bootle for river water sample collection
. Source.
Figure 3.
Dumping the bottle into the river to collect the water sample
. Source.
Figure 5.
Measuring the river water sample pH with a pH strip
. Source. The strip is compared with the color of a mobile app that gives the pH for a given strip color.
Figure 6.
Noting sample collection location on the water bottle
. Source.
Video 1.
Dumping the bottle into the river to collect the water sample
. Source. That was fun.
Because Ciro's a software engineer, and he's done enough staring in computers for a lifetime already, and he believes in the power of Git, he didn't pay much attention to this part ;-)
According to the eLife paper, the code appears to have been uploaded to: github.com/d-j-k/puntseq. TODO at least mention the key algorithms used more precisely.
Ciro can however see that it does present interesting problems!
Because it was necessary to wait for 2 days to get our data, the workshop first reused sample data from previous collections done earlier in the year to illustrate the software.
First there is some signal processing/machine learning required to do the base calling, which is not trivial in the Oxford Nanopore, since neighbouring bases can affect the signal of each other. This is mostly handled by Oxford Nanopore itself, or by hardcore programmers in the field however.
After the base calling was done, the data was analyzed using computer programs that match the sequenced 16S sequences to a database of known sequenced species.
This is of course not just a simple direct string matching problem, since like any in experiment, the DNA reads have some errors, so the program has to find the best match even though it is not exact.
The PuntSeq team would later upload the data to well known open databases so that it will be preserved forever! When ready, a link to the data would be uploaded to: www.puntseq.co.uk/data
Bisulfite sequencing by Ciro Santilli 40 Updated 2025-07-16
The main way to sequence DNA methylation. Converts methylated cytosine to uracil, and then we can sequence those.
Video 1.
Bisulfite Sequencing by Henrik's Lab (2020)
Source. Nothing much new that we don't understand from a single sentence in the animation. But hey, animations!
Makes RNA from RNA.
Used in Positive-strand RNA virus to replicate.
I don't think it's present outside viruses. Well regulated organisms just transcribe more DNA instead.
That single operon can produce two different mRNA transcription units:
The reason for this appears to be that there is a rho-independent termination region after thrL. But then under certain conditions, that must get innactivated, and then the thrLABC is produced instead.

Pinned article: Introduction to the OurBigBook Project

Welcome to the OurBigBook Project! Our goal is to create the perfect publishing platform for STEM subjects, and get university-level students to write the best free STEM tutorials ever.
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    Screenshot of the "Derivative" topic page
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    You can publish local OurBigBook lightweight markup files to either https://OurBigBook.com or as a static website
    .
    Figure 3.
    Visual Studio Code extension installation
    .
    Figure 4.
    Visual Studio Code extension tree navigation
    .
    Figure 5.
    Web editor
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    Video 3.
    Edit locally and publish demo
    . Source. This shows editing OurBigBook Markup and publishing it using the Visual Studio Code extension.
    Video 4.
    OurBigBook Visual Studio Code extension editing and navigation demo
    . Source.
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