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.

In this case when the bacteria is showing the lesser homology with the other bacterial species for the respective adhesion protein then this can be the case where the bacteria has not undergone the conjugation and the horizontal gene transfer has been taken place. This would have happened in the presence of the human cells near to the bacterial cell and thus the 90% of the homology has been seen with the humans as compared to the other bacteria based on the data relevance by NCBI. As the bacteria has occurred with the human gene in it for the adhesion purpose, it can be the possibility that cell-cell crosstalk becomes more possible for them and it is required for cell survival.But, there are different genes which are being present in the bacteria and humans but the adhesion protein obtained from the humans can not be the essential gene for the bacteria except for the adhesion and thus it can be the possibility that the bacteria must have engulfed the dead intestinal cell and the DNA must have been cross over to form the linkage that has been determined as the newer gene in the bacteria with the more similarity than other bacterial species.

Answered: 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…

Human Anatomy & Physiology (11th Edition)

11th Edition

ISBN: 9780134580999

Author: Elaine N. Marieb, Katja N. Hoehn

Publisher: PEARSON

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Question

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.

Which of the following statements about the phylogenetic tree shown here is FALSE?

Evolutionary time moves from right to left in this tree.
		The groups with the greatest number of sequence changes compared to the last common ancestor of all of the groups are E and F.
		Groups A and B are likely to share the most similarity in their DNA sequences compared to all the other groups.
		The group that is likely to have the least DNA sequence similarity to the others is C.