When I was reading through the archive, I noticed some discussion on the affect of Iodine on friendly bacteria. I notice GinaGirl chimed in with her interesting comment about making bread with iodine, and I certainly want more details about that, but she didn't say anything about yogurt or other cultures. So I devised an experiment: Make yogurt or cultured cream with and without Iodine and see whether it cultures properly.
I used a couple tablespoons of stonyfield farms yogurt, a quart of hiland heavy whipping cream, and 6 drops 5% lugols.
First I warmed up the cream (not as much as you are supposed to, but I was under some time pressure), then cooled it down below 118F and added the yogurt. I got four mugs that held about a cup, and filled the first one as an Iodine free control. Then I added three drops of Lugols to the rest. I filled the second one, so it had approximately one drop (6.25mg). Then I added two drops to the rest. Then I filled the third one, so it had approximately two drops (12.5mg). Then I added one drop to the remaining just over a cup so that it had approximately three drops (18.75mg) and poured in the last mug. I then left them in my oven's warming drawer at the bread proofing setting for 24 hours.
All four cups cultured just fine. They taste like yogurt, and are thick with a very little free whey.
I do not think this would have happened if the iodine had killed the yogurt culture, so I conclude that even 18.75mg is not enough to kill it.