Changes of gene expression in E.coli DH5α following 25 keV nitrogen ions irradiation are investigated.The results indicate:(1) The expression of total protein increases obviously after N+ ion irradiation; (2) 23 differential expression segments are separated from E.coli cells by using mRNA differential display reverse transcription-PCR (DDRT-PCR) and blot hybridization techniques,12 of them are activated (damage-induced expression),4 suppressed,6 increased and only one decreased.These experimental data suggest that the changes of gene expression of E.coli induced by low-energy ion beam are remarkable and in a diverse form.