• In the context of a research work on isolated microorganisms in the Chilean Antarctica, the research team led by Dr Claudio Vásquez, professor at the Faculty of Chemistry and Biology of Universidad de Santiago, discovered that glutathione reductase is one of the enzymes able to reduce tellurite, a compound which is highly toxic to almost all microorganisms.

Tellurium, a chemical element with symbol Te and atomic number 52, seems to be non-toxic. However, when combined with other elements like oxygen, it produces tellurite, which is very harmful to living organisms.

A research team led by Dr Claudio Vásquez studied the mechanisms that bacteria use against high concentrations of toxic metals. The results of the study were published in the American Society for Microbiology’sjournal Applied and Environmental Microbiology, USA.

This study is part of the Regular Fondecyt Project N° 1130362 “Tellurite-resistant Antarctic bacteria: Unveiling new toxicant resistance mechanisms,” which also inquired into how oxygen is partially reduced with the concomitant generation of reactive oxygen species (ROS) in the cells exposed to a toxicant. Organisms that depend on oxygen to breath live in an oxidative environment that affects their cells. Therefore, to prevent the cell’s structure and chemical composition from being damaged, they have an inner reductive environment,” he explains.

In the Antarctica

To collect the required samples, Dr Vásquez and Dr José Manuel Pérez of Universidad Andrés Bello, went to the Prat and Escudero Antarctic Bases; they visited Deception Island and Fildes Peninsula and travelled on the Almirante Óscar Viel ice-breaker of the Chilean Army.

“As the Antarctic laboratories are well equipped, we were able to process part of those samples. We wanted to isolate the Antarctic microorganisms resistant to the toxic salt tellurite that we had studied years ago at the university laboratory,” Dr Vásquez says. In the samples that they studied, they were able to isolate several tellurite-resistant bacteria.

Tellurite reduction

Dr Vásquez and his team were able to prove that glutathione reductase is responsible for reducing tellurite and, therefore, for the cell’s resistance to this toxicant.

“We purified proteins as of crude extracts of resistant bacteria and we found that a particular enzyme, glutathione reductase, was largely responsible for reducing the toxicant, as it changed it to its non-toxic metallic form,” he says.

“We tested these nanoparticles and we found that they have antibacterial properties, so they can be used to fight pathogenic bacteria that cause disease,” he adds.

It is worth to mention that the studies conducted by Dr Vásquez are eco-friendly, as he uses biosynthesis: He reduces metals by using proteins or cells and not chemical substances. In this way, it is possible to lower expenses and work at environment temperature, avoiding negative impacts on the ecosystem.

Dr Vásquez says that as tellurite is rare in the environment, it has been poorly studied and its properties are not well understood.

The research team is made up of the following members: Dr Benoit Pugin, Fabián Cornejo and Pablo Muñoz-Díaz (biochemists), Claudia Muñoz-Vilagrán, Joaquín Vargas-Pérez (biochemist) and Dr Felipe Arenas.

To read the full paper, search “Glutathione reductase-mediated synthesis of tellurium containing nanostructures exhibiting antibacterial properties” on the web.

Translated by Marcela Contreras