Search for life on other planets: chemolithotroph metabolism detection based on electrochemical methods

ALBERT SAAVEDRA; CORTÓN, EDUARDO; ABREVAYA X. C.

Lima

Congreso; I Congreso Latinoamericano de Astrobiología (I-CLA); 2016

The searchfor life on other planets, is a recurring and important issue today, on ourplanet there are diverse microorganisms that can be study models of thepossible forms of life that can be found on other planets. Thechemolithoautotrophs microorganisms, have a characteristic than they do idealfor this type of study, as they present certain characteristics, such as Acidithiobacillus ferrooxidans,acidophilic microorganism (pH 1.8), which has the peculiarity to present ascarbon source, carbon dioxide and the energy source is obtained of theoxidation of iron and sulfur. In the following research will be presented astrategy to detect this type of metabolism, using as a basis the bio-corrosionof pyrite (FeS2) in a three electrode system, was used as workingelectrode the FeS2, and studied by electrochemical, as methodslinear polarization, and calculating the potential/corrosion current by theStern-Geary equation, additionally cyclic voltammetry testing (CV). Experimentswere performed with live bacteria, dead (106 cel.mL-1)and in his absence; and presence / absence of iron. In presence and absence ofiron, it showed significant differences in the corrosion current (Icorr)calculated, being of 23, 5 and 5 μA.cm-2 (in the presence of 500 mg.L-1iron) and 6, 1, 1 µA.cm-2 (in the absence of iron), for livebacteria, dead and in his absence respectively. This difference in Icorris due to the interaction between the bacteria and mineral, as it is aphenomenon related to the increase of the electroactive area, and the corrosionmediated by this microorganism. In the CV studies we detect electro-activezones at several potentials, which may suggest the presence of elemental sulfurand jarosite. In the presence of dead bacteria, was possible to detect interactionbetween amino acids and pyrite, suggesting the detection of bacterial debris.The device we present here seems suitable for detecting microorganisms of thistype on other planets and in extreme environments.