Visualizing Microorganism-Mineral Interaction in the Iberian Pyrite Belt Subsurface: The Acidovorax Case

Abstract

Despite being considered an extreme environment, several studies have shown that life in the deep subsurface is abundant and diverse. Microorganisms inhabiting these systems live within the rock pores and, therefore, the geochemical and geohydrological characteristics of this matrix may influence the distribution of underground biodiversity. In this study, correlative fluorescence and Raman microscopy (Raman-FISH) was used to analyze the mineralogy associated with the presence of members of the genus Acidovorax, an iron oxidizing microorganisms, in native rock samples of the Iberian Pyrite Belt subsurface. Our results suggest a strong correlation between the presence of Acidovorax genus and pyrite, suggesting that the mineral might greatly influence its subsurface distribution.

Preservation of Underground Microbial Diversity in Ancient Subsurface Deposits (>6 Ma) of the Rio Tinto Basement

“…In this regard, sphingolipid synthesis has been described in few bacteria groups (e.g., CFB Group, and δ-Proteobacteria), which build outer membranes devoid of lipopolysaccharides [ 59 ]. In turn, the occurrence of amino acid fragments suggests that the molecular composition could also resulted from the mineralization of EPS, which have been found in the subsurface [ 6 , 12 ].…”

“…Interestingly, new data has shown that Acidovorax is also involved in the cycling of different compounds through redox metabolic processes using different nitrogen compounds as electron acceptors [ 6 ]. The microbial activity of such bacteria has been likely recorded in form of micron-sized microstructures that correspond to sections of filamentous sheaths enriched in nitrogen [ 15 ].…”

“…The drilling of the basement rocks accomplished by the Mars Analog and Research Technology Experiment (MARTE) and Iberian Pyrite Belt Subsurface Life (IPBSL) projects [ 6 , 7 , 8 , 9 , 10 , 11 , 12 ] has provided novel information on the living forms that are involved in the metabolic degradation of the sulfide orebodies. It shows that the Rio Tinto basement is inhabited by a very diverse bacterial community accompanied by Archaea [ 7 ], which sustain an intricate cycling network of C, H, N, S and Fe.…”

“…It shows that the Rio Tinto basement is inhabited by a very diverse bacterial community accompanied by Archaea [ 7 ], which sustain an intricate cycling network of C, H, N, S and Fe. Inside such a complex frame, the abundance of Acidovorax plays an essential role in nitrogen cycling, becoming one of the main agents for the subsurface biooxidation of the orebody [ 6 , 7 ].…”

COSC-2 – drilling the basal décollement and underlying margin of palaeocontinent Baltica in the Paleozoic Caledonide Orogen of Scandinavia

“…Flame sterilisation of the core surface was repeated until at least 99.9 % of the microspheres in the drilling liquid had been quenched (quenching of the microsphere fluorescence occurs upon heating above 100 • C). Once the core was deemed free from contamination, it was sampled for subsequent CARD-FISH analysis (fluorescence in situ hybridisation with catalysed reporter deposition; Escudero et al, 2020). Briefly, the core was transferred to the clean part of the on-site laboratory to sample the inner core, by aseptically removing small fragments, followed by fixing the material in 4 % (vol / vol) formaldehyde in Mackintosh minimal media.…”