Isolation and Plant Growth-promoting Characterization of a Salt-alkali Tolerant Bacillus cabrialesii Strain

doi:10.13560/j.cnki.biotech.bull.1985.2025-1367

Abstract

Abstract:

Objective This study aimed to isolate and screen salt-alkali tolerant plant growth-promoting rhizobacteria, thereby providing microbial resources and theoretical foundations for the development of functional microbial fertilizers and the remediation of saline-alkali soils. Method Rhizosphere soil samples were collected from cotton plants in Yingjisha County, Xinjiang. Salt-alkali tolerant bacteria were isolated and screened using the serial dilution method. The strains were identified by 16S rRNA gene sequencing, and their taxonomic status was determined based on morphological, physiological, and biochemical characteristics. Salt-alkali tolerance of the strain was assessed using media with NaCl concentrations of 0–200 g/L and pH values of 4.0–13.0. Plant growth-promoting traits, such as phosphate solubilization, siderophore production, nitrogen fixation, biofilm formation, and amylase and cellulase activities, were evaluated using specific functional media. Finally, the effect of the strain on tomato seedling growth was examined through plate and pot experiments. Result In this study, we isolated a salt-alkali tolerant strain. 16S rRNA gene sequence analysis showed that the strain shared 99.72% similarity with the type strain Bacillus cabrialesii TE3^T, and we identified it as B. cabrialesii zp-4245. Strain zp-4245 could grow under conditions of 80 g/L NaCl and pH 9.0, and exhibited multiple plant growth-promoting traits, including siderophore production, nitrogen fixation, and the production of amylase, cellulase, and biofilm. In plate assays, we found that strain zp-4245 significantly promoted the growth of tomato seedlings under different salt-alkali stress conditions. Compared with the control at pH 5.8, inoculation with the strain increased lateral root number, aboveground fresh weight, underground fresh weight, and total fresh weight by 284.3%, 87.3%, 118.4%, and 94.2%, respectively. At pH 8.0, the increases were 361.7%, 92.3%, 141.7%, and 101.9%, respectively. Under combined stress of pH 8.0 and 2.925 g/L NaCl, the lateral root number increased by 707.6% compared to the control. Pot experiments demonstrated the growth-promoting effects of strain zp-4245 on tomato plants. Under non-salt-stress conditions, inoculation with strain zp-4245 increased aboveground fresh weight and plant height by 11.7% and 13.9%, respectively. Under salt stress (6 g/kg NaCl), inoculation increased underground fresh weight and plant height by 28.6% and 10.7%, respectively, compared with the control. Conclusion B. cabrialesii zp-4245 exhibits excellent salt-alkali tolerance and plant growth-promoting capabilities, significantly enhancing tomato seedling growth under varied saline-alkaline conditions. These findings provide valuable microbial resources and a theoretical foundation for developing microbial fertilizers for saline-alkali soils improvement.

Key words: plant growth-promoting rhizobacteria, saline-alkali soil, Bacillus cabrialesii, tomato

HE Hao-di, LIANG Zhen-pu, ZHANG Guo-zhi, FANG Shi-jie, ZHANG Xiao-xia. Isolation and Plant Growth-promoting Characterization of a Salt-alkali Tolerant Bacillus cabrialesii Strain[J]. Biotechnology Bulletin, doi: 10.13560/j.cnki.biotech.bull.1985.2025-1367.

Figures/Tables 9

Fig. 1 Morphological identification of strain zp-4245A: Colonial morphology; B: gram stain

Fig. 2 Phylogenetic tree of strain zp-4245 based on 16S rRNA gene sequencesGenBank accession numbers are shown in parentheses. Bootstrap values (shown at the branches) represent the probability of the taxa being clustered together

Table 1 Physiological and biochemical analysis of strain zp-4245

测定指标 Test indicators	结果 Results
葡萄糖Glucose	+
木糖Xylose	-
果糖Fructose	+
阿拉伯糖Arabinose	-
蔗糖Sucrose	+
半乳糖Galactose	-
过氧化氢酶Catalase	+
氧化酶Oxidase	-
明胶液化Gelatin liquefaction	+

Fig. 3 Salt-alkali tolerance of strain zp-4245

Fig. 4 Growth curve of strain zp-4245

Fig. 5 Growth-promoting characteristics of strain zp-4245A: Amylase-producing ability. B: Siderophore-producing ability. C: Cellulase-producing ability. D: Nitrogen-fixing ability. Bar=1 cm

Fig. 6 Test results of biofilm formation ability of the strain zp-4245CK: Liquid LB medium without bacterial inoculation after 3 days of culture. zp-4245: Liquid LB medium inoculated with strain zp-4245 after 3 days of culture

Fig. 7 Growth-promoting effect of strain zp-4245 on tomato in plate assaysA: Growth-promoting effect of strain zp-4245 on tomato. B: Lateral root number and fresh weight of tomato. T1: pH 5.8, T2: pH 8.0, T3: pH 8.0+0.168 g/L NaHCO3, T4: pH 8.0+2.925 g/L NaCl, T5: pH 8.0+0.168 g/L NaHCO3+2.925 g/L NaCl. * P<0.05, ** P<0.01, *** P＜0.001, **** P＜0.000 1

Fig. 8 Growth-promoting effect of strain zp-4245 on tomato seedlings under different salt stress conditionsA: Growth-promoting effect of strain zp-4245 on tomato. B: Fresh weight, plant height, and root length of tomato. The percentages in the figure indicate the growth rate of each treatment group compared to the CK group

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