Identification of a New Heavy-Metal-Resistant Strain of Geobacillus stearothermophilus Isolated from a Hydrothermally Active Volcanic Area in Southern Italy

Abstract

Microorganisms thriving in hot springs and hydrothermally active volcanic areas are dynamically involved in heavy-metal biogeochemical cycles; they have developed peculiar resistance systems to cope with such metals which nowadays can be considered among the most permanent and toxic pollutants for humans and the environment. For this reason, their exploitation is functional to unravel mechanisms of toxic-metal detoxification and to address bioremediation of heavy-metal pollution with eco-sustainable approaches. In this work, we isolated a novel strain of the thermophilic bacterium Geobacillus stearothermophilus from the solfataric mud pool in Pisciarelli, a well-known hydrothermally active zone of the Campi Flegrei volcano located near Naples in Italy, and characterized it by ribotyping, 16S rRNA sequencing and mass spectrometry analyses. The minimal inhibitory concentration (MIC) toward several heavy-metal ions indicated that the novel G. stearothermophilus isolate is particularly resistant to some of them. Functional and morphological analyses suggest that it is endowed with metal resistance systems for arsenic and cadmium detoxification.

Extremophiles, a Nifty Tool to Face Environmental Pollution: From Exploitation of Metabolism to Genome Engineering

“…In particular, the term “biosorption” is referred to passive processes that follow a kinetic equilibrium, while “bioaccumulation” to energy driven processes which require active metabolism [ 63 ]. For example, heavy metals metabolic pathways have been widely investigated within the Geobacillus genus, since many members of this species are highly tolerant to various heavy metals (As, Ag, Cd, Co, Cr, Cu, Fe, Pb, U, Zn) [ 57 , 59 , 64 ]. In particular, their biosorption and bioaccumulation mechanisms have been analyzed and applied on environmental samples to remove unwanted metals [ 3 , 58 , 59 ].…”

Genomic Insight of Alicyclobacillus mali FL18 Isolated From an Arsenic-Rich Hot Spring

“…MIC toward different antibiotics was determined using a procedure previously described (Puopolo et al, 2020). In detail, the bacterial culture was diluted up to 0.1 OD 600 nm in BAT medium, pH 4.0, supplemented with concentrations ranging from 0.5 to 1,000 µg/ml of ampicillin, bacitracin, chloramphenicol, ciprofloxacin, erythromycin, kanamycin, streptomycin, tetracycline, and vancomycin, and grown at 55 • C for 16 h. MIC was evaluated by measuring OD 600 nm after incubation for 16 h in the presence of different concentrations of antibiotics.…”

Nested Formation of Calcium Carbonate Polymorphs in a Bacterial Surface Membrane with a Graded Nanoconfinement: An Evolutionary Strategy to Ensure Bacterial Survival

“…For instance, they have been observed in the hot springs of the Yellowstone National Park, in the deep sea, 9 or in a hydrothermally active volcanic area. 10 With their tolerance of toxic minerals, for instance, uranium and arsenic compounds, they also exist at mining waste disposal sites. 11 The relevance of bacterial calcium carbonate mineralization in modern and ancient geochemical cycles of C and/or Ca has been extensively studied (e.g., by Gorgen et al, 4 v. Knorre and Krumbein, 12 Boquet et al, 13 and Uriz et al 14 ).…”

“…In nature, these thermophile bacteria live not only under normal environmental conditions but also under higher temperatures. For instance, they have been observed in the hot springs of the Yellowstone National Park, in the deep sea, or in a hydrothermally active volcanic area . With their tolerance of toxic minerals, for instance, uranium and arsenic compounds, they also exist at mining waste disposal sites…”