Screening and identification of a heavy metal lead-adsorbing strain with plant growth-promoting activity

Abstract:

[Background] With the industrialization, heavy metals have been under the major environmental pollutant category. Microbial remediation has become a popular method for heavy metal removal in recent years. Thus, screening and developing related efficient microbial strains is of important practical significance. [Objective] To screen the strain with heavy metal-absorbing function and plant growth-promoting (PGP) activity, so as to provide microbial resources for both bioremediation and plant growth promotion. [Methods] The selective medium was used to screen the lead-tolerant strain from sludge. The strain was identified based on morphological observation, physiological and biochemical determination, and 16S rRNA gene sequence analysis. Through single-factor experiment, the effects of different culture conditions on the growth of the strain were analyzed. Atomic absorption spectrometry, colorimetry, and plate confrontation assay were employed to analyze the lead-absorbing efficiency, inorganic phosphorus-solubilizing ability, secretion of indole-3-acetic acid (IAA), and the ability of antagonizing Fusarium. [Results] A strain with high lead-adsorbing efficiency (over 90% for 150 mg/L Pb²⁺), which was identified as Bacillus cereus and named SEM-15, was screened out. It can solubilize inorganic phosphorus, secrete IAA, and antagonize Fusarium. Moreover, it had strong adaptability, as it survived at pH 10.0. Therefore, the strain has great potential in removing lead, promoting plant growth, and preventing diseases. [Conclusion] SEM-15, with lead-adsorbing function and PGP activity, is of great value in remediation of heavy metal-contaminated soil and plant growth.