THIS
http://hypography.com/forums/medical...tml#post101541
seems relevant somehow?
"If the mutant was broken because it could not make DMB," she said, "then if we added DMB back it should be okay. So we added DMB, and the bacteria went back to acting like ordinary [symbiotic] bacteria. That was the defining experiment."
When the researchers provided DMB so that the bacteria did not have to manufacture it themselves, the bacteria's extraordinary brilliance subsided to a more uniform fluorescence on the lab dish with the laundry whitener. And in the lab dish with the seedlings, the restored bacteria produced a bigger, healthier plant. Chemist and co-author Kavita Mistry followed up with biochemical experiments to prove that the bluB mutant could not make B12 without added DMB.
"Our findings just mean bluB is necessary for the reaction," Taga said. "We are currently doing experiments to show that it directly catalyzes the reaction."
But Roth said the discovery gives him hope for finding all the steps in the pathway for synthesizing B12. "This is the part that has resisted genetics and chemistry," he explained. "We've tried it. Others have tried it. This appears to be the first enzyme dedicated to synthesizing the part."
Other bacteria, such as the Salmonella that Roth studies, appear to substitute other molecules in place of DMB, stymieing genetic approaches. But the form of B12 that people need contains DMB.
The discovery of the bluB mutant may overturn a theory that DMB spontaneously forms without enzymes to speed up the reaction, Roth said. Before the bluB mutant was identified, that theory made sense because the reactions that make B12 do not require energy, in contrast to most biosynthetic reactions.
Taga and Walker are following up to figure out how the bluB mutation affects the symbiotic relationship between the bacteria and the plant.
