Microbiological investigation of two chondrite meteorites: Murchison and Polonnaruwa

The question of the contamination of meteorites by modern environmental microorganisms is an issue that has been raised since evidence for biological remains in carbonaceous meteorites was first published in the early 1960's.1-3 The contamination hypothesis has been raised for recent fossils of diatoms and filamentous cyanobacteria found embedded in the stones even though the nitrogen content of the fossils was below the 0.5% detection limit for Energy Dispersive X-ray Spectroscopy (EDS) of the Field Emission Scanning Electron Microscope. All modern biological contaminants should have nitrogen content in the detectable range of 2% to 20% indicating the remains are ancient fossils rather than living or Holocene cells. In our work, the possibility that extremophilic bacteria from our lab collection might be able to metabolize organic matter in the studied meteorites was tested. The potential toxic or inhibitory growth effects were also checked for different anaerobic cultures. UV exposed meteorite samples with consequent sterile extraction of the internal part were subjected to anaerobic cultivation techniques. As a result, eight anaerobic strains were isolated from internal and exterior parts of the studied meteorites. Preliminary results of their morphology, cytology, physiology, and molecular (16SrRNA sequencing) studies are presented and discussed in this article.