A bacterial species was isolated from a stool sample given by a healthy human volunteer. Researchers purified and cultured large amounts of the bacteria and sequenced its genome. They ran a comparison between the bacterial genome and the entire NCBI Genbank database (which includes the human genome sequence) and found a gene in the bacteria that showed 90% sequence homology to a human adhesion protein gene, but only 35% homology to other bacterial adhesion protein genes including those of other common gut commensal bacterial species. What conclusions could the researchers make from their results? The bacteria may have picked up and incorporated the human adhesion gene by horizontal gene transfer, after engulfing cell parts or DNA from human cells within the gut. All bacterial species living in the human gut may have originally had the adhesion protein gene that is homologous to the human version, but the gene became mutated in all the species except the one, which retained the functional version. The bacteria inhabit a common environment with cells of the large intestine, so this is a case of convergent evolution, where both types of cells need similar adhesion proteins in order to avoid being carried away by the process of peristalsis.
Bacterial Genomics
The study of the morphological, physiological, and evolutionary aspects of the bacterial genome is referred to as bacterial genomics. This subdisciplinary field aids in understanding how genes are assembled into genomes. Further, bacterial or microbial genomics has helped researchers in understanding the pathogenicity of bacteria and other microbes.
Transformation Experiment in Bacteria
In the discovery of genetic material, the experiment conducted by Frederick Griffith on Streptococcus pneumonia proved to be a stepping stone.
Plasmids and Vectors
The DNA molecule that exists in a circular shape and is smaller in size which is capable of its replication is called Plasmids. In other words, it is called extra-chromosomal plasmid DNA. Vectors are the molecule which is capable of carrying genetic material which can be transferred into another cell and further carry out replication and expression. Plasmids can act as vectors.
A bacterial species was isolated from a stool sample given by a healthy human volunteer. Researchers purified and cultured large amounts of the bacteria and sequenced its genome. They ran a comparison between the bacterial genome and the entire NCBI Genbank database (which includes the human genome sequence) and found a gene in the bacteria that showed 90% sequence homology to a human adhesion protein gene, but only 35% homology to other bacterial adhesion protein genes including those of other common gut commensal bacterial species. What conclusions could the researchers make from their results?
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The bacteria may have picked up and incorporated the human adhesion gene by horizontal gene transfer, after engulfing cell parts or DNA from human cells within the gut. |
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All bacterial species living in the human gut may have originally had the adhesion protein gene that is homologous to the human version, but the gene became mutated in all the species except the one, which retained the functional version. |
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The bacteria inhabit a common environment with cells of the large intestine, so this is a case of convergent evolution, where both types of cells need similar adhesion proteins in order to avoid being carried away by the process of peristalsis. |
Which of the following statements about the phylogenetic tree shown here is FALSE?
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Evolutionary time moves from right to left in this tree.
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The groups with the greatest number of sequence changes compared to the last common ancestor of all of the groups are E and F.
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Groups A and B are likely to share the most similarity in their DNA sequences compared to all the other groups.
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The group that is likely to have the least DNA sequence similarity to the others is C. |
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