Bacterial genomes are unstable at the time scale of evolution.Comparative genomics studies have suggested that gene content variations can be affiliated to the taxonomy,evolution,and adaption.In our laboratory,we use comparative genomics to gain insights into the taxonomy boundary,the evolutionary divergence,and the adaption strategies for marine bacteria.Based on a comprehensive genomic survey,we proposed a method for prokaryotic genus delimitation.We also performed a comparative genomics study of the marine bacterial genus Glaciecola to reveal its diversity and adaptation strategies to the cold.