Abstract
How the genomic diversity of species is driven by geographical isolation and environmental factors are not well understood for cold environments. Here, the environmental stress responses of two phylogenetically close Arcticibacter strains, A. eurypsychrophilus MJ9-5 and A. svalbardensis MN12-7, isolated from a Tibetan Plateau glacier and Svalbard soil, were analyzed. The comparative genomic analysis was performed with sixteen other related Sphingobacteriaceae species. Analyses of the relationships between growth temperature and genome composition, cold and heat shock genes showed that genomic adaption characteristics were more obvious when the strains were grouped by their upper limit in growth temperature, rather than by their minimal or optimal growth temperatures for Sphingobacteriaceae species. The very divergent genetic distance of genome fractions assigned to the functions of ‘secondary metabolism’, ‘dormancy and sporulation’ and ‘metabolism of aromatic compounds’ indicated the heterogeneous evolution of genes under different environmental pressures of the Sphingobacteriaceae species. The greatest differences between strains MJ9-5 and MN12-7 occurred in the genes devoted to the CRISPRs, osmotic adaption and metabolism of monosaccharides, nitrogen and aromatic compounds. These distinctions corresponded to two different environmental pressures, salinity and nutritional level, in the glacier ice and Svalbard soil environments.
Highlights
The adaption mechanisms of organisms in cold aquatic, glacier and permafrost environments have received wide attention[1,2,3]
Few physiological studies are conducted alongside genomic analyses; in some cases a general genomic adaption profile has been applied to all cold tolerant bacteria
The present study compared the physiological and genomic characteristics of two strains of Arcticibacter: A. eurypsychrophilus MJ9-5 and A. svalbardensis MN12-7; these were isolated from a Tibetan Plateau glacier and an Arctic Svalbard soil, respectively[15, 18]
Summary
The adaption mechanisms of organisms in cold aquatic, glacier and permafrost environments have received wide attention[1,2,3]. A strain of Planococcus halocryophilus, isolated from high Arctic permafrost, is able to grow and divide at −15 °C and analysis of the genome revealed that cold and osmotic-specific adaptive mechanisms were present, along with an increased flexibility of proteins in the organism[1]. The present study compared the physiological and genomic characteristics of two strains of Arcticibacter: A. eurypsychrophilus MJ9-5 (hereafter referred to as strain MJ9-5) and A. svalbardensis MN12-7 (hereafter referred to as strain MN12-7); these were isolated from a Tibetan Plateau glacier and an Arctic Svalbard soil, respectively[15, 18]. The aim of the present study was to clarify genomic adaptions to ice habitats alongside physiological characteristics, and to identify the genomic factors that have shaped the unique distribution of Arcticibacter. 16 other Sphingobacteriales strains, for which genomic data were available at the time of analysis, were used for comparison
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