Genomic and Expression Analyses of Cold-Adapted Microorganisms

Abstract

Examination of the transcriptome and proteome enables the investigation of the underlying gene and protein expression, respectively, that results in cold adaptation and ultimately permits the successful colonization of cold environments by cold-adapted microorganisms. Genomics can be used to investigate cold adaptation at the level of whole genes by examining gene content, gene expression, protein expression, and other unique features, while at the molecular level, genomic analyses may identify trends in amino acid composition, codon usage, and nucleotide content that result from cold adaptation. This chapter discusses (i) use of ecological information to discern cold-adapted microorganisms, (ii) unique gene- and protein-expression adaptations for coping with cold environment stresses, (iii) sequence adaptations that facilitate protein function at low temperature, and (iv) a case study comparing cold-adapted and warm-adapted species of the genus Exiguobacterium. The genera Exiguobacterium and Psychrobacter represent gram-positive and gram-negative bacteria, respectively. Strains of these two genera were among the psychrophile genomes sequenced and used, along with other examples, to illustrate various aspects of cold adaptation. Five prominent eurypsychrophiles including the permafrost firmicute E. sibiricum 255-15 have been subjected to functional genomics experimentation at low temperature. Findings from studies with these organisms with reference to other psychrophilic and mesophilic microbes where appropriate, are presented in the chapter. The results suggested that E. sibiricum requires active transport of nutrients at lower temperature to increase substrate uptake.