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From the article, the claim is that this strain of S mutans variant produces mutacin-1140 which allows it to outcompete other strains of S mutans and other Gram-positive bacteria.

I have no particular opinion about whether this claim is plausible or true, but you don't address this at all in your comment even though it's directly relevant.

For example, if this strain's production of mutacin-1140 allows it to kill other bacteria locally then it could maintain a niche despite higher pH. One way to view this is bacteriocin production substituting for lactic acid production as a weapon against competing bacteria.

Also, the percentage of the novel S mutans strain colonization is being measured in the first chart and shows initial 90%+ followed by a later drop and stabilization. It would be helpful to more directly address the evidence as presented.

EDIT: Also, this S mutans strain doesn't need to outcompete the entire existing oral microbiome. Even if mutacin-1140 is less effective than lactic acid at creating a niche, it suffices to just maintain a toehold in the microbiome while outcompeting existing acid-producing S mutans strains.

[justinclift]

> if this strain's production of mutacin-1140 allows it to kill other bacteria ...

Wonder if it could in a different direction, giving rise to other oral bacteria also unaffected by mutacin-1140?

[MostlyStable]

The mutation that allows it to produce this (and to survive it) is a naturally occurring one. This strain, with that mutation, was found in the wild, which was what gave rise to the idea to use it in this way in the first place. One of the modifications they _did_ do was to break this bacteria's lateral gene transfer machinery so that it can't spread these genes to other strains.

However it is likely that, since this one strain managed to evolve this trait, that others have as well.