Many japanese people consume a diet rich in seaweed, including the edible red alga porphyra, which is used for preparing sushi. although humans cannot digest the seaweed polysaccharides (porphyran and agarose), certain marine bacteroidetes do possess the necessary cazymes. curiously, japanese individuals frequently harbor seaweed-digesting bacteroides plebeius in their gut microbiomes, while individuals from north america do not. bacteroides plebeius is not a marine bacterium, and its close relatives cannot digest seaweed. what is the mostly likely explanation for how b. plebeius acquired functional porphyranase and agarase genes?
a. random dna inversions
b. endosymbiosis with a seaweed-digesting archaeon
c. point mutations that eventually produced functional genes
d. transfer of genes from the gut epithelial cells
e. horizontal transfer of genes from a marine bacterium

e. horizontal transfer of genes from a marine bacterium

Explanation:

Horizontal gene transfer is the transfer of genetic material from one independent mature bacterium to another and creates new gene combinations in the recipient bacterium. It mostly occurs between the bacterial of different species and is responsible for the spread of new genetic traits such as antibiotic resistance, digestion of specific substances, virulence, etc.

Transfer of genetic material from the donor to host bacteria can occur in three ways: transformation, transduction, and conjugation. According to the given information, marine Bacteroidetes have enzymes required to digest porphyran and agarose. B. plebeius might have acquired the genes for these enzymes from marine Bacteroidetes by horizontal gene transfer. This resulted in its ability to digest the marine seaweed while its close relative species cannot do so.