[Glycine betaine supplied exogenously enhance salinity tolerance of Pseudomonas putida DLL-1]

The salinity tolerance characteristic of Pseudomonas putida DLL-1 and the environmental factors affecting the salinity tolerance of DLL-1 were investigated. The result showed that the enrichment of culture medium influenced the salt tolerance of DLL-1, in complete medium DLL-1 could survive higher salinities than in chemically defined medium. When inoculated to complete medium with 1mol/L NaCl, the least initial biomass guarantee DLL-1 surviving was 1/100(V/V) of the medium volumes. But when inoculated to chemically defined medium with 1mol/L NaCl, the least initial biomass guarantee DLL-1 surviving was 1/10(V/V) of the medium volumes. The effects of glycine betaine exogenously supplied on the salinity tolerance of DLL-1 and its osmo protection mechanisms were also studied. The results indicated that the glycine betaine present externally could promote the growth of DLL-1 under high salinity. 10mg/L of exogenous glycine betaine was sufficient to promote the growth condition of DLL-1 cells under high salinities. 150mg/L glycine betaine could support DLL-1 cells grow in chemically defined medium with 1.2mol/L NaCl. The presence of glycine betaine in chemically defined medium could reduce significantly the lag time and generation time and increase the final biomass of DLL-1 under salt stress. Compared with the control without exogenous glycine betaine, the lag time of the treatment with exogenous glycine betaine could be reduced from 24h to 6h, and the generation time from 60min to 35.7min, the final OD610 value of culture increased from 1.29 to 1.57. Under osmotic stress, DLL-1 cells could synthesis glycine betaine, trehalose and free amino acid as the main compatible solute. When exogenously supplied, DLL-1 cells accumulated exogenous glycine betaine rapidly from medium to balance the extracellular osmolality instead of the synthesis of compatible solutes.