Cold Adaptation Strategies and the Potential of Psychrophilic Enzymes from the Antarctic Yeast, Glaciozyma antarctica PI12

Psychrophilic organisms possess several adaptive strategies which allow them to sustain life at low temperatures between −20 to 20 °C. Studies on Antarctic psychrophiles are interesting due to the multiple stressors that exist on the permanently cold continent. These organisms produce, among other peculiarities, cold-active enzymes which not only have tremendous biotechnological potential but are valuable models for fundamental research into protein structure and function. Recent innovations in omics technologies such as genomics, transcriptomics, proteomics and metabolomics have contributed a remarkable perspective of the molecular basis underpinning the mechanisms of cold adaptation. This review critically discusses similar and different strategies of cold adaptation in the obligate psychrophilic yeast, Glaciozyma antarctica PI12 at the molecular (genome structure, proteins and enzymes, gene expression) and physiological (antifreeze proteins, membrane fluidity, stress-related proteins) levels. Our extensive studies on G. antarctica have revealed significant insights towards the innate capacity of- and the adaptation strategies employed by this psychrophilic yeast for life in the persistent cold. Furthermore, several cold-active enzymes and proteins with biotechnological potential are also discussed.

Multilocus sequence based systematics of Pseudomonas sp. from supraglacial site of Sikkim Himalaya and their adaptational strategies

Background Being one of the most complex and diverse genera, deciphering the correct taxonomy of Pseudomonas species has always been challenging. This study investigates and resolves the taxonomic ambiguity of 11 strains of Pseudomonas obtained from the supraglacial site of East Rathong glacier. Since the supraglacial region represents an extreme, stressful environment, the inhabitant microorganisms must have evolved multiple adaptive traits that define their origin. Hence, for adaptation study, we examined the survivability of the 11 strains in physical conditions of freezing and ultraviolet radiation, and their ability to produce extracellular cold-active enzymes. Results Multilocus sequence analysis (MLSA) using five housekeeping genes (1140 polymorphic sites) supported the taxonomic assignment of these strains to Pseudomonas antarctica, further supported by their lesser mean genetic distances with P. antarctica (0.73%) as compared to P. fluorescens (3.65 %). The studied strains displayed significant tolerance to freezing for 96 hours as compared to the mesophilic control strain, while except 4 strains, all strains exhibited substantial tolerance to UV-C radiations, and all strains produced cold active enzymes as well. Conclusion MLSA successfully resolved the taxonomy of these significant group of bacteria from physical extremes of temperature and radiation. The isolates ERGC3:01 and ERGC3:05, owing to their polyadaptational attributes, may be considered promising for exploitation in various industries.

Taking Advantage of Promiscuity of Cold-Active Enzymes

Cold-active enzymes increase their catalytic efficiency at low-temperature, introducing structural flexibility at or near the active sites. Inevitably, this feat seems to be accompanied by lower thermal stability. These characteristics have made cold-active enzymes into attractive targets for the industrial applications, since they could reduce the energy cost in the reaction, attenuate side-reactions, and simply be inactivated. In addition, the increased structural flexibility could result in broad substrate specificity for various non-native substrates, which is called substrate promiscuity. In this perspective, we deal with a less addressed aspect of cold-active enzymes, substrate promiscuity, which has enormous potential for semi-synthesis or enzymatic modification of fine chemicals and drugs. Further structural and directed-evolutional studies on substrate promiscuity of cold-active enzymes will provide a new workhorse in white biotechnology.