Xy. Sun et al., LOW-TEMPERATURE GROWTH, FREEZING SURVIVAL, AND PRODUCTION OF ANTIFREEZE PROTEIN BY THE PLANT-GROWTH PROMOTING RHIZOBACTERIUM PSEUDOMONAS-PUTIDA GR12-2, Canadian journal of microbiology, 41(9), 1995, pp. 776-784
The plant growth promoting rhizobacterium Pseudomonas putida GR12-2 wa
s originally isolated from the rhizosphere of plants growing in the Ca
nadian High Arctic. Here we report that this bacterium was able to gro
w and promote root elongation of both spring and winter canola at 5 de
grees C, a temperature at which only a relatively small number of bact
eria are able to proliferate and function. In addition, the bacterium
survived exposure to freezing temperatures,i.e., -20 and -50 degrees C
. In an effort to determine the mechanistic basis for this behaviour,
it was discovered that following growth at 5 degrees C, P. putida GR12
-2 synthesized and secreted to the growth medium a protein with antifr
eeze activity. Analysis of the spent growth medium, following concentr
ation by ultrafiltration, by SDS-polyacrylamide gel electrophoresis re
vealed the presence of one major protein with a molecular mass of appr
oximately 32-34 kDa and a number of minor proteins. However, at this p
oint it is not known which of these proteins contains the antifreeze a
ctivity.