Page 2 Plant-Bacteria Interactions Edited by Iqbal Ahmad, John ...

200j 10 Principles, Applications and Future Aspects of Cold-Adapted PGPR
Figure 10.1 Mechanism of cold tolerance in microorganisms [98].
freeze-labile alkaline phosphatase (ALP) enzyme under freezing conditions as compared
to non-AFP-producing strains of P. fluorescens.
Khan [36] studied the presence of AFP from CRPF 1, a cold-tolerant mutant of P.
fluorescens. It was demonstrated that cold shock protein from CRPF1 resulted in 75%
protection of ALP against freeze inactivation. BSA was used as positive control,
which was also effective in protecting ALP against freeze inactivation. However, CSP
was superior to BSA; furthermore, sucrose did not protect ALP against freeze
inactivation and served as a negative control.
Walker and coworkers [37] reported that, at low temperatures, different microorganisms
show different types of adaptive responses, which either alter their
cellular structure or affect gene expression with decrease in temperature. Those
microorganisms that are exposed to frequent freeze-thaw challenges or are present
in temperature ranges from psychrophilic to mesophilic are more resistant to low
temperatures. It was demonstrated that when a mixture of soil isolate collected from
the Chinook zone (where temperature ranges from 35 to 35 C) along with two
control isolates, E. coli and Pseudomonas, was subjected to regular freeze-thaw up to
48 cycles, control isolates were no longer viable but bacteria from soil isolates were