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The species Colstridium ramosum DSM 1402 had a gene called CLORAM_02027 that was identified under the GC content analysis as a potential gene that has taken part in a horizontal gene transfer event in the human gut microbiome. It was identified to be 7.2658 standard deviations away from the mean (its z-score). That gene was then taken and ran through a phylogenetic analysis called Dark Horse, and was identified as similar enough to another gene that phlogenetically through things such as blast has been identified to be a part of horizontal gene transfer. The gene it has been identified to be similar to is CLOSCI_03336. This gene is know by the name of IS1 protein InsB [Escherichia coli UTI89]. This gene is 167 base pairs long."IS1 is the smallest insertion sequence in E. coli. It codes for three proteins, InsA, InsB and InsAB'.InsAB' is the transposase for IS1 [Escoubas94]. Its translation depends on a -1 frameshift within the 3' end region of insA which allows translational readthrough into insB[Sekine89]. In the absence of this frameshift, the IS1 transcriptional repressor protein InsA is produced instead." It’s biological function has been defined as transposition that is DNA-mediated. Its molecular function are DNA binding, and transposase activity. These functions are very important because they directly prove that this gene was a part of a horizontal gene transfer event. Transposases are easy links to horizontal gene transfer as they can jump from place to place so easily. They do so in either the “copy-paste” method or the “cut-paste” method but move around to alter genomes and genes. This gene most likely was transposed into the Colstridum ramosum and that is why it is so dissimilar to the rest of the Colstridum ramosum genome and why it comes up in both the GC-content analysis method and the dark horse phylogenetic analysis as a gene that contributes to horizontal gene transfer. The gene originates from E. coli, and it has been shown to create ‘pedestals’ that allow the E. coli to attach to cell walls and live in our body with little to no effort. Perhaps this is indicative of why this gene has been horizontally transferred so that it can help its species live within our body with less effort, by allowing it to attach on to our gut and live off of our human bodies. Perhaps the gene transferred over by chance and just kept being passed down. However, it is hard to tell exactly the reason for the horizontal gene transfer of this gene, but it is pretty easily stated in most literature that it was passed down by the way of transposition. Below you can see an image of how this gene is connected to several other genes involved in transposition and it can be shown that it is absolutely necessary to have this gene in order for transposition to occur. That being said this may be a sign of why it was horizontally transferred because it helps create diversity and variability within a microorganism so that it may survive more efficiently and longer within our human bodies. 

Colstridum Ramosum DSM 1402

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