> > This is very interesting ! I would bet these bugs secrete biocins of
> > sort. If biocin secretion is associated with e.g. glucose in the medium,
> > if the bug is slightly sensitive to the biocins as well, perhaps this
> > explain the weird colony formation.
>> Since all of the bacteria in the culture should carry the plasmid that
> production of the biocin, as well as the immunity protein that protects
> cells that carry the plasmid from the effects of the biocin, this is not a
> likely explanation. One *could* propose a very high rate of spontaneous
> but that is not consistent with maintenance of the plasmid and would have
> selected against.
It doesn't have to be a plasmid, though - it could be in the chromosome :)
I do agree that this explanation is stretching the limits of plausibility,