Lead absorption mechanisms in bacteria as strategies for lead bioremediation

Abstract

Bacteria exhibit a number of metabolism-dependent and metabolism-independent processes for the uptake and accumulation of toxic metals. The removal of these metals from environmental sources such as soil, sludge, and wastewaters using microbe-based technologies provide an alternative for their recovery and remediation. Lead (Pb) is a pervasive metal in the environment that adversely affects all living organisms. Many aspects of metal-microbe interactions remain unexploited in biotechnology and further development and application is necessary, particularly to the problem of Pb release into the environment. Thus, this review provides a synopsis of the most important bacterial phenotypes and biochemical attributes that are instrumental in lead bioremediation, along with what is known of their genetic background that can be exploited or improved through genetic engineering. This review also highlights the potential of Pb-resistant bacteria in bringing about detoxification of Pb-contaminated terrestrial and aquatic systems in a highly sustainable and environmental friendly manner, and the existing challenges that still lie in the path to in situ and large-scale bioremediation.

Sustainable microbial cell nanofactory for zinc oxide nanoparticles production by zinc-tolerant probiotic Lactobacillus plantarum strain TA4

“…2b, the ability of each strain was varied in various concentrations and interestingly, strain TA4 demonstrated a remarkable growth at the highest concentration of Zn 2+ , which Proposed mechanisms of bacteria in resisting metal ion and produce NPs simultaneously. Biosorption occurs on the bacterial cell wall, which involves the binding of metal cations to the negatively charged functional groups on the bacteria such as carboxyl, phosphate, and hydroxyl [22]. EPS secreted by bacteria also act as biosorption site in the form of biofilm, to tolerate metal ions by trapping them within the EPS matrix and reducing them to the less toxic metal [22].…”

“…Biosorption occurs on the bacterial cell wall, which involves the binding of metal cations to the negatively charged functional groups on the bacteria such as carboxyl, phosphate, and hydroxyl [22]. EPS secreted by bacteria also act as biosorption site in the form of biofilm, to tolerate metal ions by trapping them within the EPS matrix and reducing them to the less toxic metal [22]. Precipitation is one of the mechanisms that lower the metal ion toxicity through the reaction between anions such as hydroxyl ion and metal ions (cation) that occurs either intra-or extracellularly.…”

“…Biosorption is a passive and non-metabolically mediated process that involves binding, ion exchange, chelation and precipitation, which depend on the presence of functional groups on the bacterial cell walls [19][20][21]. This is followed by bioaccumulation, in which the metal ions will enter into the cell and react with bacterial intracellular structures [20,22]. Figure 1 proposed the mechanisms of Gram-positive bacteria in resisting metal ion and reducing it to the respective metal NPs.…”

“…However, the studies conducted on zinc-tolerant probiotic in the biosynthesis of ZnO NPs are limited. Over the last decades, there is heavy usage of probiotic due to its ability to tolerate and bind to various metal ions such as copper (Cu) [24], arsenic (As) [25], zinc (Zn) [19], cadmium (Cd) [21,22], selenium (Se), and lead (Pb) [26,27] for toxicological and environmental purposes. However, there has been no proper explanation regarding the mechanisms in which this microorganism resists to Zn 2+ and produces ZnO NPs simultaneously.…”

Pb(II) Bio-Removal, Viability, and Population Distribution of an Industrial Microbial Consortium: The Effect of Pb(II) and Nutrient Concentrations

“…These results reveal that the active species (K. pneumoniae) is not the most prevalent species in the sample, indicating that most organisms in the sample have Pb(II)-resistant properties, while not contributing to the Pb precipitation mechanism observed. It is, however, likely that the non-precipitating organisms are responsible for some of the initial Pb(II) biosorption observed in the initial 3 h [16]. Another observation worth exploring is that the species Ralstonia solanacearum was not measured in any appreciable quantities in the 80 ppm Pb samples while being the predominant species at 500 ppm Pb.…”