Characterization of Fungal Endophytes Isolated from the Metal Hyperaccumulator Plant Vachellia farnesiana Growing in Mine Tailings

Abstract

Heavy metal pollution has become an environmental and health problem worldwide. With the aim of finding novel strategies for metal bioremediation, endophytic fungi from the heavy metal hyperaccumulator plant Vachellia farnesiana were isolated and characterized. The plants were growing in mine tailings, rich in Zn, Pb, and Cu. Morphological and phylogenetic analyses indicated that the fungal strains belonged to Neocosmospora and Aspergillus genera. The Neocosmospora isolate belongs to the Fusarium solani species complex (FSSC) that groups phytopathogen species. However, in this case the plants from which it was isolated did not show any signs of disease. Both fungal strains were able to remove significant amounts of heavy metals from liquid cultures, either in a mixture of the three metals or each metal in a single culture. In response to lead exposure, the Neocosmospora sp. strain secreted specific novel phenolic compounds other than anthraquinones or naphtoquinones, which have been described in similar situations. The Aspergillus sp. dropped the pH in the medium. High-performance liquid chromatography determinations indicated that this strain secreted mainly glutamic acid in response to lead, a novel mechanism, which has not been reported elsewhere. Malic and succinic acids were also produced in response to lead exposure. Possibly, glutamic and succinic acids (synthesized in the Krebs cycle) can be used to cope with metal toxicity due to the plant providing photosynthates to the fungus. These fungi showed the potential to be used for bioremediation or restoration of metal-polluted environments.

Iron stress response and bioaccumulation potential of three fungal strains isolated from sewage-irrigated soil

“…Similarly, malic acid synthesis by Aspergillus sp. was increased around 12-fold under Pb(II) stress (Salazar-Ramírez et al, 2020). A. humicola SKP102 produces oxalic acid in response to Ni(II) stress to minimize its toxic impact (Ghosh & Paul, 2016).…”

Current Scenario and Future Prospects of Endophytic Microbes: Promising Candidates for Abiotic and Biotic Stress Management for Agricultural and Environmental Sustainability

“…However, current studies dealing with the interactions between hyperaccumulator plants and endophytes have attracted attention worldwide because of inherent pollutant removal ability and possibilities for large-scale applications [ 91 , 109 , 123 , 125 , 130 , 131 , 197 , 225 , 243 ]. Furthermore, hyperaccumulators sequester a significantly high content of hazardous heavy metals and therefore create the internal environmental conditions suitable for the development of metal resistance in endophytes exposed to high heavy metal concentrations [ 172 ].…”

A Study of Microbial Diversity in a Biofertilizer Consortium

“…CSL-1 produces indole acetic acid and gibberellins, increasing seedling biomass and chlorophyll content [86]. Some Fusarium species could promote growth by phosphate solubilization, synthesis of phytohormones, and siderophore production [96,118]. Alternatively, several biofertilizer microbial communities could produce metabolites to antagonize pathogens from the same community [93,98,119].…”