Abstract
Psychrophilic bacteria grow optimally at
temperature below 15oC. In these bacteria, heat stress
occurs at relatively low temperatures in comparison with
that in mesophilic bacteria. We have investigated the heat
shock response of a psychrophilic bacterium, Colwellia
maris ABE-1. Northern blot analysis revealed that the
level of mRNAs of groESL and dnaK was increased at
20oC, suggesting that this temperature induces the heat
shock response in this bacterium. The groESL and dnaK
of C. maris are regulated by the
32 system like those of
E. coli, although the temperature for their induction is
over 20oC lower than the case of E. coli. In C. maris, it
seems that the base pairing of the downstream box in the
mRNA secondary structure of rpoH encoding
32 should
be less stable than that of E. coli. This feature plays a key
role for the translation of
32 followed by the expression
Hsp at relatively low temperature in C. maris. The
protein folding mechanism of the GroEL system of a
psychrophilic bacterium, Colwellia psychrerythraea 34H
(CpGroEL) was also investigated. We found that ATP is
not the optimum energy source of the CpGroEL system.
Thus, we consider that the CpGroEL system possesses an
energy-saving mechanism for avoiding excess
consumption of ATP to ensure growth in a
low-temperature environment.
