Construction Of Nitric Oxide Producing Engineering Bacterial Strains And Their Plant Growth Promoting Effect To Hybrid Pennisetum Under Copper Stress

34and16endophytic bacterial strains from roots and stems of elephant grasses grown in copper polluted soil, and14bacterial strains from soils were isolated.12presumed dominant strains were chosen by the characteristic and initial amount of the clones on the plates, and identified through16S rDNA sequencing/blast method.3Pseudomonas strains were identified, which showed strong resistance against copper, as well as abilities to generate nitric oxide under denitrifying condition. Strain S3and E2e were chosen to be the starting strains of the genetic engineering construction based on their resistance against copper and antibiotics.nir was cloned from strain S3, gfp was clone from plasmid pHC60, as well as copper inducible promoter and copABCDRS gene cluster were cloned from Pseudomonas syringae pv. Tomato pPT23D. These components were ligated with modified expression vector pBBR1MCS-5-Sse, and the constructed plasmids were designated pBBR1MCS-5-Sse-CPN and pBBR1MCS-5-Sse-CPG, respectively. These two plasmids were transformed separately into strains S3and E2e, resulting in engineering strains S3-BCPN, S3-BCPG, E2e-BCPN and E2e-BCPG. Biological characteristics of starting and engineering strains were studied and no important difference except copper resistance was detected among them.GFP expression in E2e-BCPG and S3-BCPG were investigated under induction of different copper levels, and differences levels of gfp expression induced by copper were observed among the two strains.Plant growth promoting effects of strain E2e-BCPN and S3-BCPN to hybrid pennisetum seedlings under copper stress were studied. When the seedlings were grown in light incubator, strains S3-BCPN showed strong plant growth promoting effect and increased biomass amount of the seedlings, thus enhanced total amount of absorbed copper. When the seedlings were grown in green house (also suffered heat stress at the same time), strain E2e-BCPN displayed strong plant growth promoting effect and improved amount of biomass and chlorophyll of the seedlings. Since no much difference of amount of combustion calorie per gram of seedling was observed between different treatments, amount of combustion calorie per seedling was increased when seedlings were inoculated with strain E2e-BCPN.