The moon element

SynCell News • June 05, 2020

It was 1817. The Swedish chemists Jöns Jacob Berzelius and Johan Gottlieb Gahn owned a chemistry plant near Gripsholm (Sweden). The plant produced sulfuric acid (H2SO4) following a lead chamber process, which uses the mineal pyrite (Fe2S) as one of the raw materials. Tons of pyrite were brought from the close Falun mine, and after use, it created a red precipitate in the lead chambers. After a first observation, Berzelius and Gahn asumed that this red precipitate was an arsenic compound. However, they became interested on the phenomenon, reason why they decided to burn the pyrite. Right after, they observed how the red precipitate gave off a smell like horseradish, which was definitely not typical of arsenic, but similar to the one coming from the recently discovered tellurium (Te) compounds [Weeks 1932].

Newly found element similar to sulfur and tellurium

It was then when Berzelius decided to write a letter to Alexander Marcet, his close friend, and a physician, reporting that the red precipitate must have been a tellurium compound. However, the lack of tellurium materials in the Falun mine minerals eventually led Berzelius to reanalyze the red precipitate, and in 1818 he wrote a second letter to Marcet describing a newly found element similar to sulfur and tellurium [Kurokawa and Berry 2013]. Soon after, Berzelius proposed a name for this element: selenium, that came from the ancient Greek word selene, which means Moon. Undoubtedly, a good choice for a name by keeping in mind that is closely related and positioned in the periodic table with tellurium, named after the latin word tellus, which mean Earth [Weeks 1932].

Not long after its discovery, Selenium (Se) was employed in the semiconductor and electronic industries, due to its outstanding electrical properties [Oldfield 2006]. After quite a few years of technological advancements within this field, the effect of Se in the human body came to medical notice due to the intoxication of industrial workers after exposure [Medinsky et al. 1985]. A few years later, in 1954, the biochemist Jane Pinsent presented the first hints of the specific biological functions of Se in microorganisms [Pinsent 1954], which was followed by the discovery of Se as an essential and key element for the life cycles of mammaliam cells [Schwarz and Foltz 1957]. Therefore, by the end of the century, plenty of reports brought data about the presence of Se in some sets of enzymes, which led to the discovery of selenocysteine in proteins, known as the 21st amino acid [Böck et al. 1991].

Figure 1. Detoxification process followed by bacteria living in selenium deposits [Garbisu et al. 1996]. The bacteria are able to take the ions within the substrate, which are toxic to them, and transform into inocous and non toxic nanoparticles; Selenium concentrations and deposits in the United States [M. E. Thompson ; Carl Roach ; William Braddock 1956].

Se was needed for life to be as we understand it, and the scientific community realized this, discovering that bacteria have a rich and extensive molecular repertoire of organelles and biochemical functions for an efficient Se metabolism. The relationship between bacteria and Se is old, but complex. We know that Se serves as both an essential nutrient and an energy generator for some biological functions, while the presence of biogeological cycles for the element is tremendously influenced by several microorganisms [Doran 1982; Nancharaiah and Lens 2015]. Besides, the bacterial metabolism of the element has been shown to participate to all valence state transformations undergone by the chalcogen element in nature [T. Wang et al. 2010].

However, Se can also behave as a powerful toxin in some bacterial species [Eswayah, Smith, and Gardiner 2016; Khalilian, Zolfaghari, and Soleimani 2015]. Despite this, bacteria can easily achieve the detoxification of Se anions and produce nanomaterials [Y. Wang et al. 2018; Kora 2018]. One of the first reports of this Se-detoxification by bacteria was presented by Gerard et al. in 1974. They observed the formation of SeNPs in the Gram negative bacteria Escherichia coli [Gerrard, Telford, and Williams 1974]. Since then, many other bacteria have been reported to reduce Se oxyanions into the elemental form, under aerobic and anaerobic conditions, which meant no surprise with such a rich distribution in the earth’s crust (Figure 1).

Following the principles reported in these papers, our R&D team started to develop an alternative approaches to the production of SeNPs back in 2017, which culminated with a process of production that could be applied to virtually any bacterial specie that can be grown in a laboratory setting or isolated from different sources. By combining Selenium and bacteria, SynCell Biotechnology is seeking new alternatives to the current use of antibiotics.