Heavy Metal Stress, Signaling, and Tolerance Due to Plant-Associated Microbes: An Overview

Abstract

Several anthropogenic activities including mining, modern agricultural practices, and industrialization have long-term detrimental effect on our environment. All these factors lead to increase in heavy metal concentration in soil, water, and air. Soil contamination with heavy metals cause several environmental problems and imparts toxic effect on plant as well as animals. In response to these adverse conditions, plants evolve complex molecular and physiological mechanisms for better adaptability, tolerance, and survival. Nowadays conventional breeding and transgenic technology are being used for development of metal stress resistant varieties which, however, are time consuming and labor intensive. Interestingly the use of microbes as an alternate technology for improving metal tolerance of plants is gaining momentum recently. The use of these beneficial microorganisms is considered as one of the most promising methods for safe crop-management practices. Interaction of plants with soil microorganisms can play a vital role in acclimatizing plants to metalliferous environments, and can thus be explored to improve microbe-assisted metal tolerance. Plant-associated microbes decrease metal accumulation in plant tissues and also help to reduce metal bioavailability in soil through various mechanisms. Nowadays, a novel phytobacterial strategy, i.e., genetically transformed bacteria has been used to increase remediation of heavy metals and stress tolerance in plants. This review takes into account our current state of knowledge of the harmful effects of heavy metal stress, the signaling responses to metal stress, and the role of plant-associated microbes in metal stress tolerance. The review also highlights the challenges and opportunities in this continued area of research on plant–microbe–metal interaction.

Native Mycorrhizal Fungi in Land Contaminated Cr, Co and Cu

“…The microorganism resistance, refers to the ability to resist the effects of pollutants which are usually effective against them, while microorganism resistance, refers to the ability to adapt to persistent pollutants (Bhalerao, 2013). Tiwari and Lata (2018) suggest that tolerance and resistance to the toxic effects of heavy metals depend on the mechanisms involved. In short, tolerance to heavy metals can be defined as a phenomenon where resistance microorganisms increase to again heavy metal stress which can lead to poisoning.…”

“…This perspective establishes that over time, in an ecosystem, exposure to heavy metal contamination increases tolerance to the community of microorganisms (Shade et al, 2012). Tiwari and Lata (2018) showing that long-term exposure heavy metals in puts pressure on soil microbes and increases tolerance. They concluded that the long-term accumulation of heavy metals in the soil gave the time to community of microorganisms to adapt to heavy metals.…”

De novoβ-alanine synthesis in α-proteobacteria involves a β-alanine synthase from the uracil degradation pathway

“…An important characteristic of the α-proteobacteria is its genome plasticity that allows different genome rearrangements including deletions or duplications (14, 15). We made a phylogenetic analysis to get a wider view on the evolutionary relationship among the ADCs from α- and γ-proteobacteria This ML-based tree inferred from the α- and γ-proteobacteria ADCs is shown in fig.…”

Changes in leaf morphological and anatomical characters of some plant species in response to gemstone mining in southwestern Nigeria

“…These strategies evidently engender alterations to a number of morphological attributes of such plants. In addition, these responses have been shown to be species-specific with different plant species responding differently to even the same level of pollution (Shahid et al, 2015;Fashola et al, 2016;Tiwari and Lata, 2018). However, understanding the mechanism of the survival strategies or adaptive modifications of these plants in response to heavy metal pollution is ver y cr ucial.…”

“…Pollution from metal mining is one of the most serious environmental problems in our contemporary environment (Singh et al, 2011;Chen et al, 2018). Generally, mine tailings are a major source of contaminants of heavy metals in water, soil and biota (Nwuche and Ugoji, 2008;Tiwari and Lata, 2018). Also, soil contamination with heavy metals may cause changes in the composition of soil microbial community, thereby adversely altering soil characteristics (Kurek and Bollag, 2004;Fashola et al, 2016).…”