And excellent growth without arsenate in every container...
As I had planned, I mixed the cells (about 10^5 cfu/ml) with 500 ml of medium, then split the medium in two parts, adding arsenate to one half and the same volume of water to the other. Then I distributed the cultures among all the containers and put them in the 28 °C incubator for about 36 hr (sitting on the shelf, not agitated in any way). (The biggest bottles, the orange-capped ones I mixed the initial cultures in, were in the 30 °C room.)
The containers with the blue '-' labels have no arsenate, those with the orange '+' labels have 40 mM arsenate.
The complete lack of growth of the arsenate cultures in the screw-capped glass tubes contradicts my previous results. Might growth in arsenate depend on gentle mixing as well as on mysterious unidentified factors? (This shouldn't matter since the cells are motile...)
This is ridiculous. I don't think I've ever had such blatantly non-reproducible results before. All I can think of to do next is to once again test growing cultures in glass screw-capped tubes, in medium with and without arsenate. But even if the cells grow with arsenate in this next test, I won't have any idea why, or why they didn't in this experiment. And anyway this experiment clearly says the problem isn't the containers.
Readers, any ideas?