Wednesday, October 1, 2014
009 - A Non-Gummy Chromogenic Strain of Azotobacter vinelandii
A popular wild-type Azotobacter vinelandii strain at the time was Wisconsin strain O, which was sometimes difficult to work with because it became "gummy," that is, kind of slimy and mucusy. This was due to alginate production, which helped production nitrogenase from oxygen.
So Bush and Wilson were trying to isolate a stable, non-gummy strain that would be easier to study. Eventually they found one that made dense, slime-free colonies on Burk agar plates, and once sure they had a pure culture, they called it A. vinelandii OP (now also called CA). This strain still produced its nice, yellow-green azotobactin pigment for iron-gathering.
Even in liquid, OP didn't become gummy, like other strains did. So they had found something useful. Later studies, especially sequencing the genome (023), revealed that a transposon had knocked out an alginate regulatory protein in OP.
Citation: Bush, J. A. & Wilson, P. W. A Non-Gummy Chromogenic Strain of Azotobacter vinelandii. Nature 184, 381–381 (1959).