北极海冰假交替单胞菌属细菌的多样性、系统分类及生态适应的遗传与生理基础

Low temperature and high salinity of sea ice are big challenges for metabolism of microorganisms. Bacteria from genus Pseudoalteromonas are found from different habitats of global oceans and have abilities to adapt to different environments. Yu et al. (2009) reported that, Pseudoalteromonas are dominant in the cultivable sea ice bacteria from Canadian Basin, Arctic. The aim of this project is to perform comprehensive studies of diversity, classification and ecological adaptation of sea ice Pseudoalteromonas. Firstly, based on the genome sequencing of 26 type strains of this genus, this project will disclose the genes related to the production of bioactive compounds and extracellular enzymes and reveal insights into the mechanism of its adaptation to ocean environments. Secondly, this project will develop a method for systematic classification of Pseudoaltermonas strains and classify the over 200 sea ice strains of Pseudoalteromonas from Canadian Basin, based on the molecular markers and physiological studies. Candidate new species will be studied with polyphasic approach. Thirdly, genomes of typical sea ice strains will be sequenced and the nutrition mechanism and the cold adaptation and salt tolerant mechanism will be studied on the basis of comprehensive genome annotation and comparative studies. Lastly, comparative transcriptomic studies will be performed to uncover the mechanism of adaptation to low temperature and high salinity of sea ice and how the sea ice bacteria quickly respond to the change of environments. This project will elucidate the diversity, classification as well as the nutrition mechanism of sea ice Pseudoalteormonas and give insights into the genetic and physiological mechanism of adaptation to sea ice.

海冰低温、高盐，对微生物生理代谢有重要影响。假交替单胞菌属（Pseudoalteromonas）细菌在全球海洋广泛分布，具有很强的环境适应能力。Yu等（2009）研究表明，在北极加拿大海盆的可培养海冰菌株中，假交替单胞菌属是优势属。本项目在前期收集该属模式菌株和基因组测序基础上，揭示该属所产生物活性物质、胞外酶的种类及其适应海洋环境的生理特点；建立基于分子标记基因的系统分类方法，对加拿大海盆200余株该属海冰菌株进行系统发育分析，结合生理生化实验进行多样性分析和系统分类，发现潜在新种；对典型海冰菌株进行基因组测序，揭示海冰菌株的营养机制和适冷、耐盐机制。综上，本项目将全面揭示假交替单胞菌属海冰菌株的多样性、系统分类和营养机制，阐明该属细菌适应海冰环境的遗传和生理机制。

假交替单胞菌是在全球海洋广泛分布的γ变性菌纲的一个细菌属，在包括海冰、深海等极端环境在内的多种海洋环境中生存。本项目系统研究了假交替单胞菌的基因组的多样性和分类以及对海冰菌株的适应。首先，开展了该属26个种的模式菌株的全基因组测序和比较基因组学研究，阐明了该属各个种的系统发育关系和各个家系在基因组成上的差异。随后，本项目筛选了用于该属快速分类的分子标记基因，并对海冰菌株进行了分类。最后，本项目开展了典型海冰菌株的基因组学研究，系统注释和分析了海冰菌株用于耐受低温、高盐等极端环境的基因（簇），发现多数海冰菌株基因组中存在大量水平基因转移事件，这些水平转移的基因（簇）很可能提高了菌株对重金属的耐受能力。本项目研究结果一方面为进一步开展海洋微生物生理、进化、生态等的研究提供了丰富的基因组数据，另一方面，本项目研究结果显示，假交替单胞菌属的模式菌株以及海冰菌株的多样性非常高，对应的基因组差异很可能暗示了对不同类型环境的适应策略。因此，在本项目基础上，加强对差异基因功能的实验验证，将深化对海洋微生物的分类、生理、遗传和生态等多方面认识，并有望做出新的重要发现。