intensity from 15 to 0
C, but the most evident was two proteins CspA and glutathione S-transferase (GST), which indicated that these proteins were responsible for
cold adaptation at near-freezing temperature (Wang et al. 2006).
In recent study, adaptation of Salmonella enterica sv. typhimurium at refrigerated
temperatures involves induction of a multigenic cold shock response (CSR) where
gene expression is co-ordinately modified, to express cold shock proteins (Csps).
Characterization of CspA instigated the identification of other CspA paralogues,
which are highly conserved and widespread across species. Six CspA paralogues
have previously been identified in S. typhimurium with comparing a csp null strain
that lacking all CspA paralogues. This csp null strain is unable to grow following
cold shock, demonstrating that the CspA paralogues play an essential role during
low temperature adaptation. The individual CspA paralogues exhibit distinct expression profiles, including expression of CspC and CspE at optimal temperature and
CspA and CspB following cold shock. This work investigates the transcriptional
changes of S. typhimurium during cold shock and the role of the CspA paralogues
under both optimal and cold shock conditions (Woodall et al. 2011).
6.12 Regulation of Major Cold Shock and Cold
Acclimation Genes
Responses to cold shock might be controlled at the transcriptional or translational
level, though these two possibilities are not mutually exclusive. Two kinds of
proteins are mainly synthesized after downshift of temperature: the so-called cold
shock proteins (CSPs) or class I protein, whose level increases sharply for short
period within the lag phase and second one is cold-acclimation proteins (CAPs) or
class II protein, the level of which increases gradually to a moderate level and does
not fall as fast as CSPs (Ray 2006). Examples of the class I protein include cold
shock proteins CspA, CspB, CspG, CspI, RNA helicase CsdA ribosome binding
protein RbfA, transcription factor NusA, and exoribonuclease PNPase. The class II
includes histone-like protein H-NS, recombination protein RecA, DNA gyrase
subunit A, translation initiation factor IF2α, trigger factor (TF), pyruvate dehydrogenase subunit E1, and dihydrolipoamide dehydrogenase (Thieringer et al. 1998;
Yamanaka 1999; Jones et al. 1987). Thus, there is a distinct change in protein
profiles of bacteria during acclimatization to lower temperature. After the temperature downshift the cold shocked cells resume multiplication, transcription and
translation of housekeeping genes and continue the synthesis of Caps for some
more time before reaching to the steady state level of growth. The growth rate at
low temperature is slower and hence all the metabolic activities are adjusted to the
new rate. In fact, global analysis of protein profiles (proteome) in few bacteria
suggests a change in large number of proteins in cell at low temperature, and the
pattern of change is more complex than the induction of 1–2 dozen of new proteins,
the understanding of which in relation to low temperature biology is only beginning
to unfold (Phadtare and Inouye 2004, Kaan et al. 2002).
6 Plant Growth Promoting Rhizobacteria: Mechanisms and Alleviation of Cold Stress. . . 201
C, but the most evident was two proteins CspA and glutathione S-transferase (GST), which indicated that these proteins were responsible for
cold adaptation at near-freezing temperature (Wang et al. 2006).
In recent study, adaptation of Salmonella enterica sv. typhimurium at refrigerated
temperatures involves induction of a multigenic cold shock response (CSR) where
gene expression is co-ordinately modified, to express cold shock proteins (Csps).
Characterization of CspA instigated the identification of other CspA paralogues,
which are highly conserved and widespread across species. Six CspA paralogues
have previously been identified in S. typhimurium with comparing a csp null strain
that lacking all CspA paralogues. This csp null strain is unable to grow following
cold shock, demonstrating that the CspA paralogues play an essential role during
low temperature adaptation. The individual CspA paralogues exhibit distinct expression profiles, including expression of CspC and CspE at optimal temperature and
CspA and CspB following cold shock. This work investigates the transcriptional
changes of S. typhimurium during cold shock and the role of the CspA paralogues
under both optimal and cold shock conditions (Woodall et al. 2011).
6.12 Regulation of Major Cold Shock and Cold
Acclimation Genes
Responses to cold shock might be controlled at the transcriptional or translational
level, though these two possibilities are not mutually exclusive. Two kinds of
proteins are mainly synthesized after downshift of temperature: the so-called cold
shock proteins (CSPs) or class I protein, whose level increases sharply for short
period within the lag phase and second one is cold-acclimation proteins (CAPs) or
class II protein, the level of which increases gradually to a moderate level and does
not fall as fast as CSPs (Ray 2006). Examples of the class I protein include cold
shock proteins CspA, CspB, CspG, CspI, RNA helicase CsdA ribosome binding
protein RbfA, transcription factor NusA, and exoribonuclease PNPase. The class II
includes histone-like protein H-NS, recombination protein RecA, DNA gyrase
subunit A, translation initiation factor IF2α, trigger factor (TF), pyruvate dehydrogenase subunit E1, and dihydrolipoamide dehydrogenase (Thieringer et al. 1998;
Yamanaka 1999; Jones et al. 1987). Thus, there is a distinct change in protein
profiles of bacteria during acclimatization to lower temperature. After the temperature downshift the cold shocked cells resume multiplication, transcription and
translation of housekeeping genes and continue the synthesis of Caps for some
more time before reaching to the steady state level of growth. The growth rate at
low temperature is slower and hence all the metabolic activities are adjusted to the
new rate. In fact, global analysis of protein profiles (proteome) in few bacteria
suggests a change in large number of proteins in cell at low temperature, and the
pattern of change is more complex than the induction of 1–2 dozen of new proteins,
the understanding of which in relation to low temperature biology is only beginning
to unfold (Phadtare and Inouye 2004, Kaan et al. 2002).
6 Plant Growth Promoting Rhizobacteria: Mechanisms and Alleviation of Cold Stress. . . 201