Thus, another polymicrobial interaction that contributes to BV symptomology!

However, Dialister lacks the upstream enzymes to fully convert arginine into putrescine, and it relies on other bacteria such as Fannyhessea vagine to cross-feed it putrescine precursors.

I found putrescine-producing enzymes in our metaproteomic data matching proteins from Dialister micraerophilus, and indeed, that species can make high concentrations of multiple malodorous compounds!

The second cool story here is around putrescine. As you can probably tell by the name, putrescine does not smell good, and high concentrations of the compound likely contribute to BV-associated malodor.

So this seems to be a really elegant syntrophic interaction where other bacteria get to use a fermentation pathway that maximizes their ATP yield, DNF00809 gets an exclusive energy source, and at the same time, the entire community is protected from acid!

But it turns out a yet-unnamed bacterium, DNF00809, can consume formic acid made by other bacteria, increasing the pH of its media in the process.

Most surprising: At least 12 species of BV-associated bacteria ferment high concentrations of formate. That was unexpected because formic acid is even more acidic than lactic acid which commensal lactobacilli produce, inhibiting the growth of those dysbiotic organisms.