Biotechnology Bulletin ›› 2023, Vol. 39 ›› Issue (5): 276-285.doi: 10.13560/j.cnki.biotech.bull.1985.2022-1292

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Isolation and Identification of Bacterial Strain C8 and B4 and Their Halotolerant Growth-promoting Effects and Mechanisms

CHE Yong-mei(), GUO Yan-ping, LIU Guang-chao, YE Qing, LI Ya-hua, ZHAO Fang-gui, LIU Xin()   

  1. Key Lab of Plant Biotechnology in Universities of Shandong Province/Life Science College, Qingdao Agricultural University, Qingdao 266109
  • Received:2022-10-19 Online:2023-05-26 Published:2023-06-08
  • Contact: LIU Xin E-mail:yongmeiche@163.com;liuxin6080@126.com

Abstract:

Soil salinization is one of the critical adverse environmental factors affecting agricultural crop growth and yield, and rational use of growth-promoting rhizotrophic bacteria is an effective way to improve and amend salinized soil. In the present study, two halotolerant bacterial strains C8 and B4 were isolated from saline soil in Dongying city, Shandong province. Through morphological observation, physiological and biochemical tests combined with 16S rDNA and gyrB gene sequence analysis, C8 and B4 were identified as Microbacterium oxydans and Stenotrophomonas maltophilia respectively. The results on the LB medium with NaCl showed that the C8 tolerated 6% NaCl, and had the abilities of dissolving potassium, organic and inorganic phosphorus as well as producing auxin. Strain B4 tolerated 8% NaCl, it was capable of solubilizing organic phosphorus and producing auxin. Using tomato as material, the effects and mechanism of sole inoculation with C8 or B4 and simultaneous inoculation of C8 and B4 on the seed germination and plant growth were investigated under salt stress. The results demonstrated that sole C8 or B4 inoculation and the simultaneous inoculation of C8 and B4 significantly promoted tomato seed germination and seedling growth, increased catalase(CAT)and peroxidase(POD)activities, and up-regulated the expressions of catalase gene CAT1 and CAT2. C8 and B4 application enhanced plant K+ content, but reduced Na+ content and Na+/ K+, and up-regulated the expression of vacuolar membrane Na+/H+ antiporter gene NHX1 and NHX3. Simultaneous application of C8 and B4 showed synergistic effect. The above results indicate that C8 and B4 enhance antioxidant capacity, maintain ion homeostasis in plants by regulating the expression of antioxidant enzyme and Na+ transporter genes, thus improve plant salt tolerance.

Key words: Microbacterium oxydans C8, Stenotrophomonas maltophilia B4, isolation and identification, tomato, salt tolerant and growth- promoting effect