Blue Bacterial Culture without X-gal - (Sep/21/2011 )
I have seen this happen once a long time ago, but I can't remember what we determined to be the cause. We set up about 24 miniprep cultures in LB broth innoculated from single colonies on LB+Amp agar plate. After 18 h of growth, 2 cultures out of the 24 were greenish blue (yellow of the LB plus Blue color from ?). When we pelleted the cells, the pellets seemed larger than the others, and upon lysis and precipitation the pellets were gooey-er than the others. This media (Plates or Broth) did not contain X-gal, and all cultures were started using the same bottle of media, so it must be something the cells are doing.
Contamination with Pseudomonas aeruginosa?
Chromobacterium violaceum? got picture?
No picture, since we processed the samples for DNA extraction. As it turns out, neither of the samples contained plasmid DNA, so they were obviously ampicillin resistant contaminants, but I don't know why they would generate white colonies on an LB+Amp agar plate and generate blue-green culture in LB Broth.
Regardless, I am pretty sure that it was Pseudomonas aeruginosa, since we did notice that the cultures had sort of a musty grape smell to them. Thanks to bob1 for the suggestion!