falls, the lag phase that precedes growth extends leading to a decrease in the growth
rate and the final cell number. The cold temperature largely alters the fluidity of lipid
bilayer which in turn affects the solute transport system across it. The lipid bilayer
which is the basic structure of the microbial membranes must have proper fluidity to
maintain the cell permeability and movement of essential solutes. The functional
state of this bilayer is a liquid-crystalline phase, but a decline in temperature induces
a gel phase transition and a drastic loss of the membrane properties. The effect of the
rapid cold shock on the membrane was found to correlate with high rates of cell
inactivation (90 and 70%) in E. coli and Bacillus subtilis, respectively. Thus,
membrane alternation seems to be the principal cause of cold shock injury in
E. coli and Bacillus subtilis (Hoang et al. 2007). Cold stress also induces a shift in
the carbon source utilization and enhances the susceptibility of bacteria to antibiotics
(Ponder et al. 2005). In some bacteria, production of pigments and other enzymatic
activities are enhanced at low temperatures, e.g. lipase and proteinase production by
Pseudomonas and certain other genera occur preferentially at low temperatures
(Witter et al. 1966; Olson and Nottingham 1980). The prior temperature history of
the cell has been found to be an important factor for the survival and growth of
organisms because of its effects on the extent of lag phase before the onset of growth
(Dufrenne et al. 1997).
6.4
Determinants of Cold Tolerance in Bacteria
6.4.1 Sensing of Cold Temperature
Survival at low temperature would depend on the ability of the sensor to perceive the
signal and to transduce the signal to the genome that resulted up-regulation of genes,
whose products might be involved in cold adaptation (Fig. 6.1). Bacterial temperature sensing appears to be located in the ability of bacterial cell to define and locate
those defined changes in its biomolecular constitution that occur as physicochemical response to temperature changes (Eriksson et al. 2002). Bacterial temperature sensing via alteration in nucleic acid or protein conformation, or changes in
membrane lipid behavior, as sensing devices has been reported (Eriksson et al. 2002)
(Fig. 6.1).
6.4.1.1 Signal Transduction
Decrease in membrane fluidity due to cold serves as a primary signal for cold
perception. A two-component signal transduction system consisting of a membrane
based sensory kinase and a cytoplasmic response regulator is reported to constitute
the signal transduction reaction in different bacteria (Suzuki et al. 2001; Los et al.
2008). This two-component signal transduction system is known as the phosphortransfer pathway. In this system, there is a transfer of a phosphate moiety from the
sensor to the response regulator. The sensor is normally an integral membrane
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rate and the final cell number. The cold temperature largely alters the fluidity of lipid
bilayer which in turn affects the solute transport system across it. The lipid bilayer
which is the basic structure of the microbial membranes must have proper fluidity to
maintain the cell permeability and movement of essential solutes. The functional
state of this bilayer is a liquid-crystalline phase, but a decline in temperature induces
a gel phase transition and a drastic loss of the membrane properties. The effect of the
rapid cold shock on the membrane was found to correlate with high rates of cell
inactivation (90 and 70%) in E. coli and Bacillus subtilis, respectively. Thus,
membrane alternation seems to be the principal cause of cold shock injury in
E. coli and Bacillus subtilis (Hoang et al. 2007). Cold stress also induces a shift in
the carbon source utilization and enhances the susceptibility of bacteria to antibiotics
(Ponder et al. 2005). In some bacteria, production of pigments and other enzymatic
activities are enhanced at low temperatures, e.g. lipase and proteinase production by
Pseudomonas and certain other genera occur preferentially at low temperatures
(Witter et al. 1966; Olson and Nottingham 1980). The prior temperature history of
the cell has been found to be an important factor for the survival and growth of
organisms because of its effects on the extent of lag phase before the onset of growth
(Dufrenne et al. 1997).
6.4
Determinants of Cold Tolerance in Bacteria
6.4.1 Sensing of Cold Temperature
Survival at low temperature would depend on the ability of the sensor to perceive the
signal and to transduce the signal to the genome that resulted up-regulation of genes,
whose products might be involved in cold adaptation (Fig. 6.1). Bacterial temperature sensing appears to be located in the ability of bacterial cell to define and locate
those defined changes in its biomolecular constitution that occur as physicochemical response to temperature changes (Eriksson et al. 2002). Bacterial temperature sensing via alteration in nucleic acid or protein conformation, or changes in
membrane lipid behavior, as sensing devices has been reported (Eriksson et al. 2002)
(Fig. 6.1).
6.4.1.1 Signal Transduction
Decrease in membrane fluidity due to cold serves as a primary signal for cold
perception. A two-component signal transduction system consisting of a membrane
based sensory kinase and a cytoplasmic response regulator is reported to constitute
the signal transduction reaction in different bacteria (Suzuki et al. 2001; Los et al.
2008). This two-component signal transduction system is known as the phosphortransfer pathway. In this system, there is a transfer of a phosphate moiety from the
sensor to the response regulator. The sensor is normally an integral membrane
190
P. K. Mishra et al.