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识别太空中的微生物
国际空间站上生活着什么？《识别太空中的微生物》一文首先出现在《走向数据科学》上。
来源:走向数据科学在国际空间站生活了四分之一个多世纪。 As the old tomato at the back of your fridge will tell you, that’s plenty of time to start growing mould. What microbes are tough enough to survive on the International Space Station with stellar radiation and no gravity? We can find the answer using metagenomics.
Let’s walk through how to find out what’s living on the International Space Station. You take your unlabelled DNA sequence and try to find a very similar sequence from a known species, which is very similar to searching for similar documents or web pages.因此，生物学家基于局部敏感散列的思想来识别物种。 Here I’ll go through the code, discuss the results (including a surprisingly tasty find), and describe the algorithm used to identify species. Once you understand these techniques you can go and find out what mould is living anywhere in the solar system!
In metagenomics, rather than studying the DNA of just one organism, you look at the DNA of all the different species in one place. This paper by Urbaniak et al.used metagenomics to study all the bacteria and fungi from 8 different locations around the International Space Station. We’ll focus on just one of their samples; they took a piece of cloth (sterile, scientific cloth) and wiped it on the dining table, extracted all the DNA from that cloth, and sequenced it. Because this was a metagenomic study, the sampling method captures DNA from anything that might be living on the table.至关重要的是，在宏基因组学中，您无需知道其中有什么，就可以查看 DNA。
Analysing the DNA
Urbaniak et al. made their sequencing data available from the Sequence Read Archive under a creative commons zero licence. I downloaded sample F4_S5_P from the European Nucleotide Archive because it’s easier to work with.如果您想选择不同的样本，您可以在 NASA 网站上查看它们来自空间站周围位置的所有详细信息。