Low Temperature Adaptive Mechanism Of Deep-sea Bacterium Shewanella Psychrophila WP2

The low-temperature characteristics of deep sea makes deep sea microorganisms possess the psychrophilic property and evolve a variety of complex adaptation mechanisms.Shewanella genus is representative deep-sea bacterium and one of the dominant populations in deep-sea sediments.Therefore,it is of great significance to explore the temperature adaptation mechanism of deep-sea bacteria,Shewanella.This research takes the deep sea psychrophilic bacteria Shewanella psychrophila WP2 as the object focus on the temperature adaptation during the dynamic growth process.The intracellular redox state,energy and carbon source utilization and metabolic regulation of WP2 during different growth stages under different temperature are detected.The differences in gene expression at different growth stages and different temperatures are further explored to investigate temperature-adaptability characteristics of deep sea psychrophilic S.psychrophila WP2.Genome of psychrophilic deep-sea bacteria WP2 is currently the largest one of the sequenced Shewanella species.WP2 genome owns up to 17 gene islands,by which WP2 acquires a large number of accessory genes,enhancing its nitrogen utilization capacity,motility and chemotaxis,quorum sensing and antibiotic secretion.All of these functions allow WP2 to adapt to the ecological niches of oligotrophic and complex environment.Through the detection of intracellular ATP and reducing power of WP2 and the utilization of carbon source,it was found that during the growth process,temperature affected the energy production and substrates utilization of deep-sea psychrophilic bacteria S.psychrophila WP2,resulting in a special physiological characteristic,energy utilization and metabolic patterns under low temperature.WP2 can accumulate the largest biomass at low temperature which is closer to in situ environmental conditions.Under low temperature conditions,the concentration of intracellular ATP is in a very low range.The redox state of WP2 cells showed different patterns in the growth phase due to different temperatures,while WP2 always keeps in a reductive state during the mid-late exponential phase.There are a large number of gene response to temperature changes in WP2 under different growth phases,and the differentiated gene expression in response to temperature changes is a dynamic process across various growth phases.Although hundreds of genes are differentially expressed,only 26 key genes keep continuously up-or down-regulated to response to low temperature environmental conditions during any growth phase,such as phosphoenolpyruvate carboxykinase,malate synthase,ribosome alternative rescue factor ArfA,OHCU decarboxylase,allantoinase and so on.Based on the genome scale metabolic model of S.psychrophila WP2,the pathways involved in amino acid metabolism,nucleotide metabolism and folate metabolism are closely related to temperature adaptability.By transcriptome analysis,several functions like gluconeogenesis,fatty acid synthesis and purine metabolism play an important role in the temperature adaptability of WP2.The research is to reveal the temperature adaptability of S.psychrophila WP2 from the cellular level and to explore the adaptability of life to extreme environments from top to down in terms of energy regulation,substance utilization and gene expression.