Processing of Metals and Metalloids by Actinobacteria: Cell Resistance Mechanisms and Synthesis of Metal(loid)-Based Nanostructures

Abstract

Metal(loid)s have a dual biological role as micronutrients and stress agents. A few geochemical and natural processes can cause their release in the environment, although most metal-contaminated sites derive from anthropogenic activities. Actinobacteria include high GC bacteria that inhabit a wide range of terrestrial and aquatic ecological niches, where they play essential roles in recycling or transforming organic and inorganic substances. The metal(loid) tolerance and/or resistance of several members of this phylum rely on mechanisms such as biosorption and extracellular sequestration by siderophores and extracellular polymeric substances (EPS), bioaccumulation, biotransformation, and metal efflux processes, which overall contribute to maintaining metal homeostasis. Considering the bioprocessing potential of metal(loid)s by Actinobacteria, the development of bioremediation strategies to reclaim metal-contaminated environments has gained scientific and economic interests. Moreover, the ability of Actinobacteria to produce nanoscale materials with intriguing physical-chemical and biological properties emphasizes the technological value of these biotic approaches. Given these premises, this review summarizes the strategies used by Actinobacteria to cope with metal(loid) toxicity and their undoubted role in bioremediation and bionanotechnology fields.

Anaerobiosis favors biosynthesis of single and multi-element nanostructures

“…In this line, bacteria-producing metal nanomaterials with antimicrobial properties are a realistic biotechnological promise toward sustainability [5]. Bacteria reduce metal ions, chalcogens oxyanions, or other elements using NADH-or NADPH-dependent reductases, catalases, and terminal oxidases or by non-enzymatic routes such as thiol groups, and phosphates, among others [6][7][8][9].…”

Rhodococcus strains as a good biotool for neutralizing pharmaceutical pollutants and obtaining therapeutically valuable products: Through the past into the future

“…Rhodococcus spp. are able to bioconvert toxic metal(loid)s generating nanostructures with biomedical, electronic, and environmental applications ( Presentato et al, 2018b , c , 2019 , 2020 ). For instance, R .…”

Contrasted microbial community colonization of a bauxite residue deposit marked by a complex geochemical context

“…Despite their ability to lower their intracellular pH and salinity, haloalkaliphilic species must still be able to secrete stable and operational enzymes at elevated pH and salinity (Mamo, 2020), making BRDAs potential sources of these enzymes. Some of the haloalkaliphilic bacteria known to synthesize alkaline-active enzymes, namely Gammaproteobacteria, Actinobacteria and Firmicutes (Kalwasińska et al, 2018;Litchfield, 2011;Maharaja et al, 2018;Shameer, 2016;Shivlata and Tulasi, 2015), are also capable to modify the chemical phase and mobility of various critical metals (Chidambaram et al, 2010;Presentato et al, 2020;Wee et al, 2014), including REEs. For example, Maleke et al (2019) reported the direct reduction of Eu 3+ to Eu 2+ by Clostridium sp.…”