Screening and biodiversity analysis of cultivable inorganic phosphate–solubilizing bacteria in the rhizosphere of Hydrilla verticillata

methods have the advantages of low environmental disturbance, no secondary pollution, and are conducive to the self-sustaining balance of aquatic ecosystems, and have broad application prospects in the treatment of polluted water [2]. Hydrilla verticillata is a perennial submerged plant that grows and distributes in lakes, ponds and rivers. Hydrilla verticillata is adapted to the environment faster after artificial trans- plantation and grow faster compared with other submerged plants, so the absorption of nutri- ent salts, such as nitrogen and phosphorus, is also more desirable [3], which can be used for the restoration of water. However, Hydrilla verticillata is highly resistant and invasive [4]. In high–organic matter water, the growth of Hydrilla verticillata is inhibited. Sediment is one of the main factors affecting the growth of submerged plants and plays a decisive role in the growth, morphology and distribution characteristics of submerged plants [5, 6]. Submerged plants, such as Hydrilla verticillata, are often plagued by problems such as high–load sediment stress during restoration [7]. The high nutrient salts in sediment can stress the seed germina- tion and seedling growth of submerged plants, and even have toxic effects, thus affecting the ecological recovery process of the whole water. The high–organic matter content will cause the sediment to become reductive silt, which has a stressful effect on submerged plants and is not conducive to the survival and germination of submerged plants [8]. To overcome this draw-

back, there is an urgent need to develop a technology that can promote the conversion of insol- uble phosphorus in the water into soluble phosphorus that can be absorbed and utilized by Hydrilla verticillata, as well as promote the growth of Hydrilla verticillata in high–organic mat- ter polluted water. Inorganic phosphate–solubilizing bacteria (IPB) in the rhizosphere of Hydrilla verticillata can convert insoluble inorganic phosphorus in the environment into solu- ble phosphorus that can be easily absorbed and utilized [9]. Hydrilla verticillata absorbs phos- phorus through roots and leaves to promote their own growth. At present, more studies on IPB in the environment have been reported, and these studies mainly focused on the research direction of IPB in soil crop rhizosphere [10]. Researchers have isolated bacterial strains with good phosphate-solubilizing ability from rhizosphere soil of crops and have conducted studies on phosphate-solubilizing characteristic and prolifera- tion characteristic of the strains [11–15]. Although more researchers have studied IPB in soil and other environments, relatively few studies have been conducted on IPB in the rhizo- sphere of submerged plants. Studies on IPB in more polluted water, such as landscape water, lakes, and black and odorous water, are scarce. In recent years, the effect of submerged plants on the phosphorus content in their rhizosphere soil sediments has attracted widespread attention. Wang Lizhi et al. [16] found that the alternating growth process of Hydrilla verti-

cillata in the decaying phase and miner’s grass in the growing phase caused the migration of phosphorus from the aqueous phase to the sediment phase, thus keeping the phosphorus concentration of each form in the aqueous phase at a relatively low level. However, the effect of IPB on the phosphorus content in the rhizosphere sediment of submerged plants and the promotion effect of IPB on the growth and development of submerged plants are less studied. Therefore, this research aimed to use the NBRIP medium to screen for efficient cultivable IPB from the roots and rhizosphere sediments of Hydrilla verticillata, in high–organic matter urban landscape water in Chuangzhi Park, Pidu District, Chengdu, Sichuan Province, explore their biodiversity, and clarify the phosphate-solubilizing capacity of IPB in the rhizosphere of Hydrilla verticillata. The IPB screened in this research can be developed into microbial bacte- rial agents to act on the rhizosphere of submerged plants, providing phosphorus and other nutrients to submerged plants, which is important for the restoration of submerged plants in polluted water with high–organic matter, the treatment of polluted water and the ecological restoration of water. PLOS ONE Screening and biodiversity analysis of cultivable inorganic phosphate–solubilizing bacteria PLOS ONE | https://doi.org/10.1371/journal.pone.0297047 January 19, 2024 2 / 11 nlm.nih.gov/. Accession numbers of IPB strains are within the manuscript. Funding: This research was funded by the Key Laboratory Open Project of Southwest Jiaotong

University (ZD2022210017). This research was funded by Student Research Training Program (2023145). Competing interests: The authors have declared that no competing interests exist.