Price et al. [(1999). J. Bacteriol. 181:2358–2362] conducted a genetic study of the toxin transport protein (PA) of Bacillus anthracis, the bacterium that causes anthrax in humans. Within the 2294-nucleotide gene in 26 strains they identified five point mutations—two missense and three synonyms—among different isolates. Necropsy samples from an anthrax outbreak in 1979 revealed a novel missense mutation and five unique nucleotide changes among ten victims. The authors concluded that these data indicate little or no horizontal transfer between different B. anthracis strains.

On what basis did the authors conclude that evidence of horizontal transfer is absent from their data?

Video transcript

Alright, everyone. Welcome back. Let's look at our next problem. Besides traditional microbiological techniques, a variety of molecular biological methods have been described for the selective identification of B anthracis. Most of them use specific genes or proteins as targets for recognition and discrimination from related microorganisms. Genomic methods target unique gene sequences located on plasmids or in bacterial chromosomes. The differentiation of B anthracis from be serious sense. A strict o solely based on chromosome markers is difficult due to the and our answer choices, we have two different answers and then we've got C is both A and B and D is none of these. So we have both possibilities of both of these being correct and none of these being correct. So let's think about what the question is asking us. Let's talk about differentiating between the bacteria that causes anthrax and the bacteria. Be serious sense a strict. Oh And it's saying if you're just looking at chromosomal factors, how is it difficult to differentiate between these two? So let's look at choice. A Joyce says identification of B cereus group members other than B anthracis using genomic markers was impossible until very recently due to a lack of a genomic based classification of this group. Well, this is correct only recently. Um Were they completely sequenced and able to distinguish between the two um based just on genomic information? So of course, if you don't have that thorough information and complete information about the genomes of both organisms, it can be difficult to look just for genomic targets to distinguish between the two. So we'll mark that is correct since obviously, we have the possibility that we've got two more than one correct answer choice. B says anthrax like symptoms can also be caused by organisms with chromosomal features that are more closely related to be serious, but which carry these virulent genes on to plasmids that largely resemble the B anthracis virulence plasmids. Well, this is also correct. Um we have the possibility of horizontal gene transfer between bacteria and toxin genes are particularly prone to this horizontal gene transfer and sometimes up to about 30 to as much as 32% of the bacterial genome can be a result of this horizontal gene transfer resulting in a great amount of similarity between bacterial genomes. And in this case, yes, the P X 01 and P XO two plasmids and anthrax are necessary for anthrax disease symptoms to develop. But if a bacteria more closely related to the B cereus carries plasma is very similar to the P X one X 02, it can cause anthrax like symptoms and due to the similarity in those plasmids. Um If you're looking for say a genome target and the plasmids, it might be difficult to distinguish between those two different bacteria because there's so much similarity in the plasma genome. So our answer here, obviously, we can eliminate none of these. So we've got two correct answers. So our answer is going to be choice. See both A and B describe why the differentiation of B anthracis from be serious census trick toe solely based on chromosomal markers is difficult. See you in the next video.