A Mini-Review on the Co-growth and Interactions Among Microorganisms (Fungi and Bacteria) From Rhizosphere of Metal-Hyperaccumulators

Abstract

The co-growth and synergistic interactions among fungi and bacteria from the rhizosphere of plants able to hyper accumulate potentially toxic metals (PTMs) are largely unexplored. Fungi and bacteria contribute in an essential way to soil biogeochemical cycles mediating the nutrition, growth development, and health of associated plants at the rhizosphere level. Microbial consortia improve the formation of soil aggregates and soil fertility, producing organic acids and siderophores that increase solubility, mobilization, and consequently the accumulation of nutrients and metals from the rhizosphere. These microorganism consortia can both mitigate the soil conditions promoting plant colonization and increase the performance of hyperaccumulator plants. Indeed, microfungi and bacteria from metalliferous soils or contaminated matrices are commonly metal-tolerant and can play a key role for plants in the phytoextraction or phytostabilization of metals. However, few works deepen the effects of the inoculation of microfungal and bacterial consortia in the rhizosphere of metallophytes and their synergistic activity. This mini-review aimed to collect and report the data regarding the role of microbial consortia and their potentialities known to date. Moreover, our new data had shown an active fungal-bacteria consortium in the rhizosphere of the hyperaccumulator plant Alyssoides utriculata.

Effects of Bacterial and Fungal Inocula on Biomass, Ecophysiology, and Uptake of Metals of Alyssoides utriculata (L.) Medik.

“…Indeed, some PGPB have potential for phytoremediation purposes [ 30 ]. Among these, Pseudomonas fluorescens complex Migula, 1895 are ubiquitous in rhizospheric microbiota [ 31 ] and tolerant to metals [ 32 , 33 ]. These bacterial strains were also able to increase crop yield (e.g., Solanum tuberosum L.) [ 34 ], growth parameters (e.g., Pisum sativum L., up to 45%; Phaseolus vulgaris L., up to 20%) [ 35 ], and shoot dry biomass (e.g., Eragrostis tef (Zucc) Trotter, up to 2.8-fold) [ 36 ].…”

“…[ 32 ] rhizosphere as synergically able to co-grow in a mixed culture, developing a biofilm where the two microorganisms merge and reach their mature stages [ 41 ]. Their synergistic behavior suggests their potential use as in vivo microorganism consortia to mitigate metal stress and promote metal uptake for bioremediation purposes [ 33 ].…”