Abstract
Extremophiles are organisms able to thrive in extreme environmental conditions and some of them show the ability to survive high doses of heavy metals thanks to defensive mechanisms provided by primary and secondary metabolic products, i.e., extremolytes, lipids, and extremozymes. This is why there is a growing scientific and industrial interest in the use of thermophilic bacteria in a host of tasks, from the environmental detoxification of heavy metal to industrial activities, such as bio-machining and bio-metallurgy. In this work Thermus thermophilus was challenged against increasing Pb2+ concentrations spanning from 0 to 300 ppm in order to ascertain the sensitiveness of this bacteria to the Pb environmental pollution and to give an insight on its heavy metal resistance mechanisms. Analysis of growth parameters, enzyme activities, protein profiles, and lipid membrane modifications were carried out. In addition, genotyping analysis of bacteria grown in the presence of Pb2+, using random amplified polymorphic DNA-PCR and DNA melting evaluation, were also performed. A better knowledge of the response of thermophilic bacteria to the different pollutants, as heavy metals, is necessary for optimizing their use in remediation or decontamination processes.
Highlights
Pb is a known human, animal, and environmental toxic metal
We studied here the effects of Pb on the growth kinetic characteristics of the thermophilic bacteria Thermus thermophilus in order to give an insight on its Pb2+ resistance patterns by challenging it against increasing metal concentrations spanning from 0 to 300 ppm
DNA and membrane lipids were extracted from bacterial cells, grown in presence of 100 ppm of Pb2+ and harvested after 3, 6, and 24 h
Summary
Pb is a known human, animal, and environmental toxic metal It occurs naturally in the Earth’s crust as Pb compounds and it is characterized by technological properties as high density, ductility, malleability, poor electrical conductivity, high corrosion resistance, and a low melting point [1,2,3,4]. During the industrial period the use of Pb increased considerably, along with its environmental pollution and human toxicity, due to the high quantity of this metal added, inadvertently or through improper waste disposal, to water, soil and air [7]. Many different products containing Pb, such as gasoline, cosmetics, water pipes, painting, and car batteries, heavily contribute to the global lead environmental contamination [1]
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