ADAPTATION TO LOW-TEMPERATURE AND REGULATION OF GENE-EXPRESSION IN ANTARCTIC PSYCHROTROPHIC BACTERIA

Exposure to extremes of temperatures cause stresses which are sometime s lethal to living cells. Microorganisms in nature, however, are extre mely diverse and some of them can live happily in the freezing cold of Antarctica. Among the cold adapted psychrotrophs and psychrophiles, t he psychrotrophic bacteria are the predominant forms in the continenta l Antarctica. In spite of living in permanently cold area, the antarct ic bacteria exhibit, similar to mesophiles, 'cold-shock' response albe it at a much lower temperatures, e.g., at 0-5 degrees C. However, beca use of permanently cold condition and the long isolation of the contin ent, the microorganisms have acquired new adaptive features in the mem branes, enzymes and macromolecular synthesis. Only recently these adap tive modifications are coming into light due to the efforts of various laboratories around the world. However, a lot more is known about ada ptive response to low temperature in mesophilic bacteria than in antar ctic bacteria. Combined knowledge from the two systems is providing us eful clues to the understanding of basic biology of low temperature gr owing organisms. This article will provide an overview of this area of research with a special reference to sensing of temperature and regul ation of gene expression at lower temperature.