Bao Yu-Qing, Zhang Meng-Ting, Feng Bao-Yun, Jieensi Wulale, Xu Yu, Xu Lu-Rong, Han Ying-Ying, Chen Yun-Peng
Department of Resources and Environment, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai, 200240, China.
School of Health Science and Engineering, University of Shanghai for Science and Technology, Shanghai, 200093, China.
Curr Microbiol. 2023 Jan 2;80(2):58. doi: 10.1007/s00284-022-03160-5.
Nitrogen is an important factor affecting crop yield, but excessive use of chemical nitrogen fertilizer has caused decline in nitrogen utilization and soil and water pollution. Reducing the utilization of chemical nitrogen fertilizers by biological nitrogen fixation (BNF) is feasible for green production of crops. However, there are few reports on how to have more ammonium produced by nitrogen-fixing bacteria (NFB) flow outside the cell. In the present study, the amtB gene encoding an ammonium transporter (AmtB) in the genome of NFB strain Kosakonia radicincitans GXGL-4A was deleted and the △amtB mutant was characterized. The results showed that deletion of the amtB gene had no influence on the growth of bacterial cells. The extracellular ammonium nitrogen (NH) content of the △amtB mutant under nitrogen-free culture conditions was significantly higher than that of the wild-type strain GXGL-4A (WT-GXGL-4A), suggesting disruption of NH transport. Meanwhile, the plant growth-promoting effect in cucumber seedlings was visualized after fertilization using cells of the △amtB mutant. NFB fertilization continuously increased the cucumber rhizosphere soil pH. The nitrate nitrogen (NO) content in soil in the △amtB treatment group was significantly higher than that in the WT-GXGL-4A treatment group in the short term but there was no difference in soil NH contents between groups. Soil enzymatic activities varied during a 45-day assessment period, indicating that △amtB fertilization influenced soil nitrogen cycling in the cucumber rhizosphere. The results will provide a solid foundation for developing the NFB GXGL-4A into an efficient biofertilizer agent.
氮是影响作物产量的重要因素,但化学氮肥的过量使用导致了氮利用率下降以及土壤和水污染。通过生物固氮(BNF)减少化学氮肥的使用对于作物绿色生产是可行的。然而,关于如何使固氮细菌(NFB)产生的更多铵离子流出细胞的报道很少。在本研究中,删除了NFB菌株根际科萨科尼亚菌GXGL - 4A基因组中编码铵转运蛋白(AmtB)的amtB基因,并对△amtB突变体进行了表征。结果表明,amtB基因的缺失对细菌细胞的生长没有影响。在无氮培养条件下,△amtB突变体的细胞外铵态氮(NH)含量显著高于野生型菌株GXGL - 4A(WT - GXGL - 4A),表明NH转运受到破坏。同时,使用△amtB突变体的细胞施肥后,黄瓜幼苗的促生长效果得以显现。NFB施肥持续提高黄瓜根际土壤pH值。短期内,△amtB处理组土壤中的硝态氮(NO)含量显著高于WT - GXGL - 4A处理组,但两组土壤NH含量没有差异。在45天的评估期内土壤酶活性有所变化,表明△amtB施肥影响了黄瓜根际土壤的氮循环。这些结果将为把NFB GXGL - 4A开发成一种高效生物肥料提供坚实基础。