Screening， Identification， and Whole-genome Analysis of a Cadmium-tolerant Plant Growth-promoting Bacterium

doi:10.13560/j.cnki.biotech.bull.1985.2025-1193

Abstract

Abstract:

Objective This study aimed to isolate cadmium-tolerant plant growth-promoting bacteria from heavy metal-contaminated soil, evaluate their cadmium resistance and growth-promoting functions, and provide microbial resources for the bioremediation of cadmium-polluted farmland and the development of plant growth-promoting biofertilizers. Method Soil samples from Weihui county, Xinxiang city, Henan province were used to isolate strains using a cadmium-containing medium. Potassium solubilization, siderophore production, and indole-3-acetic acid (IAA) production were determined by flame photometry, chrome azurol S (CAS) assay, and the Salkowski colorimetric method, respectively. Dominant strains were further identified through morphological, physiological, biochemical, and 16S rDNA sequencing analyses, and whole-genome sequencing was performed. Bioinformatics tools were used for genome assembly, functional annotation, and mining of genes related to cadmium resistance and plant growth promotion. Wheat and maize seed germination experiments were conducted to analyze the effects of bacterial strains on germination rate, shoot length, and root length under cadmium stress. Result Eight cadmium-tolerant strains were isolated. Strain F2 showed the strongest tolerance to cadmium and was identified as Bacillus altitudinis. After 72 h of culture in LB medium with 50 mg/L Cd²⁺, strain F2 demonstrated a cadmium removal rate of 27.59%, produced 31.72 μg/mL IAA, released 23.10 mg/L soluble potassium, and showed siderophore production with a relative activity of 65.30%. Whole-genome sequencing revealed a chromosome size of 3 718 742 bp, a GC content of 41.34%, and 3 726 predicted genes, along with 79 tRNA and 24 rRNA genes. Functional annotation indicated that the strain carried multiple genes associated with heavy metal tolerance and plant growth promotion. Under cadmium stress, strain F2 significantly increased the germination rate, shoot length, and root length of wheat and maize seeds. Conclusion Bacillus altitudinis F2 is a cadmium-tolerant strain with multiple plant growth-promoting traits. Whole-genome analysis reveals the genetic basis for its cadmium resistance and growth-promoting capabilities. The strain significantly enhances seed germination and seedling growth under cadmium stress, demonstrating its potential for use as a microbial fertilizer.

Key words: cadmium-tolerant bacteria, cadmium removal rate, growth promotion, whole-genome analysis, Bacillus altitudinis, environmental microorganisms

GUO Jia-xin, WANG Meng-xia, MA Yao-wu, ZHANG Qi-yu, ZHANG Zhen-yu, LIU Hai-tao, PEI Jiu-bo, JIANG Ying. Screening， Identification， and Whole-genome Analysis of a Cadmium-tolerant Plant Growth-promoting Bacterium[J]. Biotechnology Bulletin, 2026, 42(7): 257-268.

Figures/Tables 11

References 35

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菌株 Strains	Cd²⁺浓度 Cd²⁺ concentration （mg/L）
菌株 Strains	10	25	50	100	150	200
B2	+++	+++	++	+	-	-
D1	+++	++	+	-	-	-
D2	+++	++	++	+	-	-
D3	+++	++	+	-	-	-
F1	+++	++	++	+	-	-
F2	+++	+++	+++	++	+	-
F3	+++	+++	++	+	-	-
F31	+++	++	+	-	-	-

菌株 Strains	Cd²⁺浓度 Cd²⁺ concentration （mg/L）
菌株 Strains	10	25	50	100	150	200
B2	+++	+++	++	+	-	-
D1	+++	++	+	-	-	-
D2	+++	++	++	+	-	-
D3	+++	++	+	-	-	-
F1	+++	++	++	+	-	-
F2	+++	+++	+++	++	+	-
F3	+++	+++	++	+	-	-
F31	+++	++	+	-	-	-

项目 Item	F2	参比菌株B. altitudinis 41KF2B^［27］ Reference strain B. altitudinis 41KF2B
过氧化氢酶 Catalase	+	+
甲基红 Methyl red（MR）	-	-
VP实验 Voges-Proskauer test（VP test）	+	-
革兰氏染色 Gram staining	+	+
淀粉水解 Starch hydrolysis	-	+
明胶水解 Gelatin hydrolysis	+	+
硝酸盐还原 Nitrate reduction	+	-
ONPG试验 ONPG assay	+	+

项目 Item	F2	参比菌株B. altitudinis 41KF2B^［27］ Reference strain B. altitudinis 41KF2B
过氧化氢酶 Catalase	+	+
甲基红 Methyl red（MR）	-	-
VP实验 Voges-Proskauer test（VP test）	+	-
革兰氏染色 Gram staining	+	+
淀粉水解 Starch hydrolysis	-	+
明胶水解 Gelatin hydrolysis	+	+
硝酸盐还原 Nitrate reduction	+	-
ONPG试验 ONPG assay	+	+

特征 Features	染色体 Chromosome
Size （bp）	3 718 742
G+C content （%）	41.34
tRNA	79
rRNA	24
Total number of CDSs	3 726
CDSs with NR number assignments	3 722
CDSs with COG number assignments	3 026
CDSs with GO assignments	1 754
CDSs with KEGG pathway	2 781
CDSs with TCDB assignments	1 754