Cold Temperature Adaptation and Growth of Microorganisms

Abstract

Most microorganisms must accommodate a variety of changing conditions and stresses in their environment in order to survive and multiply. Because of the impact of temperature on all reactions of the cell, adaptations to fluctuations in temperature are possibly the most common. Widespread in the environment and well-equipped for cold temperature growth, psychrophilic and psychrotrophic microorganisms may yet make numerous adjustments when faced with temperatures lower than optimum. Phospholipid and fatty acid alterations resulting in increased membrane fluidity at lower temperatures have been described for many cold tolerant microorganisms while others may make no similar adjustment. While the enzymes of cold growing bacteria have been less extensively studied than those of thermophilic bacteria, it appears that function at low temperature requires enzymes with flexible conformational structure, in order to compensate for lower reaction rates. In many organisms, including psychrophilic and psychrotrophic bacteria, specific sets of cold shock proteins are induced upon abrupt shifts to colder temperatures. While this cold shock response has not been fully delineated, it appears to be adaptive, and may function to promote the expression of genes involved in translation when cells are displaced to lower temperatures. The cold shock response of Escherichia coli has been extensively studied, and the major cold shock protein CspA appears to be involved in the regulation of the response. Upon cold shock, the induction of CspA and its counterparts in most microorganisms studied is prominent, but transient; studies of this response in some psychrotrophic bacteria have reported constitutive synthesis and continued synthesis during cold temperature growth of CspA homologues, and it will be interesting to learn if these are common mechanisms of among cold tolerant organisms. Psychrotrophic microorganisms continue to be a spoilage and safety problem in refrigerated foods, and a greater understanding of the physiological mechanisms and implications of cold temperature adaptation and growth should enhance our ability to design more effective methods of preservation.

Escherichia coli in the Environment: Implications for Water Quality and Human Health

“…Until relatively recently, however, E. coli was believed to survive poorly in the environment, and not to grow in secondary habitats, such as water, sediment, and soil 116) . E. coli faces many stresses in the environment, including low and high temperatures 7,48,74,76,93,115) , limited moisture 8,13,19,20,30,76,93,115) , variation in soil texture 30,39,76) , low organic matter content 97,115) , high salinity 97) , solar radiation 110) , and predation 12,14,19,25,93) . Recent studies, however, have shown that E. coli can survive for long periods of time in the environment, and potentially replicate, in water, on algae, and in soils in tropical 16,19,20,22,37,38) , subtropical 30,93) , and temperate environments 9,17,20,48,49,61,99,109) .…”

The Role of Cold-Shock Proteins in Low-Temperature Adaptation of Food-Related Bacteria

“…Due to the increased time intervals between production and consumption of food products and the extended use of refrigerators, notably the risks of food borne psychrotrophic pathogens, such as Listeria monocytogenes, Yersinia enterocolitica, Bacillus cereus and non-proteolytic Clostridium botulinum increased (ABEE and WOUTERS, 1999). Research on cold adaptation of bacteria focuses on the genetic and physiological processes involved in low-temperature adaptation (BERRY and FOEGEDING, 1997;YAMANAKA et aI., 1998;GRAUMANN and MARAHIEL, 1998). A thorough understanding of the cold-adaptation process can be instrumented in optimizAbbreviations: CSP -(7 kDa) cold-shock protein CIP -(non-7 kDa) cold-induced protein 5'-UTR -5'-untranslated leader CS-box -cold-shock box DB -downstream box RNP-l (and 2) -RNA-binding region 1 (and 2) ing fermentations at low temperature and may offer insight into methods to control the growth of spoilage and pathogenic bacteria, which will positively affect the shelf-life and safety of refrigerated foods.…”

“…Mechanisms that permit low-temperature growth of microorganisms include modifications in DNA supercoiling, maintaining membrane fluidity, regulating uptake and synthesis of compatible solutes, production of cold-shock proteins, modulating mRNA secondary structure and, more generally, maintaining the structural integrity of macromolecules and macromolecule assemblies, such as ribosomes (see reviews by JAENICKE, 1991;BERRY and FOEGEDING, 1997;GRAUMANN and MARAHIEL, 1998). Negative DNA supercoiling of the bacterial nucleoid increases at low temperature and this has important consequences for the regulation of transcription (DRLICA, 1992).…”

Temperature- and Surfactant-Induced Membrane Modifications That Alter Listeria monocytogenes Nisin Sensitivity by Different Mechanisms

“…The concept of membrane fluidity covers the thermal mobility of membrane proteins as well as the microviscosity of the membrane lipid bilayer (33). However, the primary way that bacteria maintain constant membrane fluidity at different growth temperatures is by adjusting their fatty acid compositions (1,5,29). For instance, there are higher proportions of short-chain and/or branched-chain fatty acids and unsaturated fatty acids in cold-tolerant bacteria.…”