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Vol.:(0123456789)Current Microbiology (2025) 82:438 https://doi.org/10.1007/s00284-025-04393-wGrowth Promotion of Maize Exposed to Arsenic and Mercury with a Consortia of Rhizosphere Bacteria Isolated from Mining TailingsDaniel Rojas?Solis 1  · Yolanda Magdalena García Rodríguez 1  · John Larsen 1  · Gustavo Santoyo 2  · Roberto Lindig?Cisneros 1Received: 9 January 2025 / Accepted: 12 July 2025 / Published online: 6 August 2025 © The Author(s) 2025AbstractIn this study we evaluated plant growth promotion (PGP) traits of bacteria associated with maize (Zea mays L.) including Pseudomonas sp. (TL36), Staphylococcus sp. (TL49), Gottfriedia sp. (TL52), and Bacillus sp. (TL80), isolated from min-ing tailings, when exposed to mercury and arsenic. Initially, the response of the bacteria to the heavy metals studied were evaluated in in vitro assays, showing regular-moderate tolerance to arsenic and low tolerance to mercury. Also plant growth promotion traits of the bacteria were studied in in vitro assays in terms of production of indole-3-acetic acid (IAA), phosphate solubilization, siderophores and biof i lm when exposed to arsenic and mercury. In addition, production of volatile organic compounds by the four bacteria were measured. In general, bacterial PGP traits were maintained when exposed to arsenic though some dif f erences were observed between bacteria and individual PGP trait. On the other hand, all the PGP traits were strongly reduced when exposed to mercury for all bacteria. Also, the compatibility between the four bacteria was examined in vitro. From the abovementioned results two consortia were established based on the TL36 and TL80 (consortium 1) and, TL49 and TL52 consortium 2, which were tested for plant growth promotion after single or multiple inoculations in maize exposed to arsenic and mercury. Single and multiple inoculation, with consortium 1 with Pseudomonas sp. and Bacillus sp. increased maize plant growth similarly, while on the other hand, consortium 2 with Staphylococcus sp. and Gottfriedia sp. had no ef f ect on maize plant growth. Despite the observed moderate tolerance to arsenic of bacteria in consortium 1, the observed plant growth promotion was mitigated in the presence of arsenic.IntroductionHeavy metal contamination is one of the most relevant prob-lems in contemporary agriculture. Their high toxicity and ability to accumulate in soils and crops represent a serious threat to agricultural production and human health [1]. Mine tailings have been identif i ed as one of the most important sources of pollution. Particularly, abandoned mines could increase the content of heavy metals in surface- and ground-water, sediments, and agricultural soils [2, 3].Heavy metals are highly toxic compounds that can persist in the soil for a long time, particularly arsenic and mercury, which can also mix with agricultural soil if mining activi-ties are carried out nearby [4]. Mercury is a persistent and mobile element, and its volatility, renders it unstable [5]. Mercury contamination in soil is associated with a toxic ef f ect on humans and ecosystems, causing changes in mem-brane permeability, changes in the structure of macromol-ecules, induces oxidative stress and mitochondrial dysfunc-tion, in addition to increasing reactive oxygen species [6].It is estimated that the total global amount of mercury accumulated in the soil environments range from 200 to 300 mg  kg −1 , so the concern generated by this element is magnif i ed due to its ability to accumulate in dif f erent trophic levels in food chains [7]. Arsenic is a metalloid that occurs in the environment in dif f erent oxidation states including As (+ 3), As (0), and As (+ 5). It is highly toxic to plants, animals, and humans, causing disturbances by inhibiting the * Daniel Rojas-Solis drojas@cieco.unam.mx1 Laboratorio Nacional de Innovación Ecotecnológica para la Sustentabilidad, Instituto de Investigaciones en Ecosistemas y Sustentabilidad, Universidad Nacional Autónoma de México, Morelia, Michoacán, Mexico2 Laboratorio de Diversidad Genómica, Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Edifcio A1’, Ciudad Universitaria, 58063 Morelia,  Michoacán, Mexico