Outer space mutation of violacein-producing bacterium was carried out by the space piggyback of manned spacecraft Shenzhou-7.The original strain for the mutation was engineered by introducing violacein-synthesizing gene cluster into Citrobacter freundii.The plate screening and liquid fermentation experiments showed that the mutation ratio of violacein-producing strain reached to 70%

and the mutation range for violacein productivity was from -61.2% to 7.3％.The violacein concentration produced by the selected efficient strain MS4 was 2.16 g·L-1 using 0.45% (vol) of glycerol as the carbon source in shake flask culture for 32 h at 20℃

which was about 143.8% higher than that produced by the original engineered strain.By serial subculture experiment

HPLC

and DNA sequencing

the screened mutant strain showed high genetics stability and obvious difference from the original strain on the component of crude violaceins

but there was no change in the DNA sequence of the violacein biosynthesis gene cluster

indicating that the space piggyback is likely having impacts on the gene regulatory networks of space-mutated strain.