Search

The advent of microfluidics has revolutionized the way we understand how microorganisms propagate through microporous spaces. Here, we apply this understanding to the study of how endolithic environmental microorganisms colonize the interiors of sterile rock. The substrates used for our study are stony meteorites from the Nullarbor Plain, Australia; a semiarid limestone karst that provides an ideal setting for preserving meteorites. Periodic flooding of the Nullarbor provides a mechanism by which microorganisms and exogenous nutrients may infiltrate meteorites. Our laboratory experiments show that environmental microorganisms reach depths greater than 400 μm by propagating through existing brecciation, passing through cracks no wider than the diameter of a resident cell (i.e., ∼5 μm). Our observations are consistent with the propagation of these eukaryotic cells via growth and cell division rather than motility. The morphology of the microorganisms changed as a result of propagation through micrometer-scale cracks, as has been observed previously for bacteria on microfluidic chips. It has been suggested that meteorites could have served as preferred habitats for microorganisms on ancient Mars. Based on our results, the depths reached by terrestrial microorganisms within meteorites would be sufficient to mitigate against the harmful effects of ionizing radiation, such as UV light, in Earth's deserts and potentially on Mars, if similar processes of microbial colonization had once been active there. Thus, meteorites landing in ancient lakes on Mars, that later dried out, could have been some of the last inhabited locations on the surface, serving as refugia before the planet's surface became inhospitable. Finally, our observations suggest that terrestrial microorganisms can colonize very fine cracks within meteorites (and potentially spaceships and rovers) on unexpectedly short timescales, with important implications for both recognition of extraterrestrial life in returned geological samples and planetary protection. [ABSTRACT FROM AUTHOR]

Background: Nelson Bay orthoreovirus (NBV) was first isolated over 40 years ago from a fruit bat in Australia. Normally, NBV does not cause human diseases, but recently several NBV strains have been associated with human respiratory tract infections, thus attracting clinical attention. Autophagy, an evolutionarily conserved process in eukaryotic cells, degrades intracellular substrates, participates in multiple physiological processes, and maintains cellular homeostasis. In addition, autophagy is intimately involved in viral infection. Methods: A new strain of NBV, isolated from a patient with a respiratory tract infection who returned to Japan from Bali, Indonesia, in 2007, was used in this study. NBV was rescued using a reverse genetics system involving cotransfection of BHK cells with 11 plasmids (pT7-L1 MB, pT7-L2 MB, pT7-L3 MB, pT7-M1 MB, pT7-M2 MB, pT7-M3 MB, pT7-S1 MB, pT7-S2 MB, pT7-S3 MB, pT7-S4 MB, and pcDNA3.1-T7), yielding NBV-MB. Recovered viruses were confirmed by immunofluorescence. The effect of NBV-MB on autophagy was evaluated by measuring the LC3-I/II proteins by immunoblot analysis after infection of BHK cells. Furthermore, after treatment with rapamycin (RAPA), 3-methyladenine (3-MA), chloroquine (CQ), or plasmid (GFP-LC3) transfection, the changes in expression of the LC3 gene and the amount of LC3-I/II protein were examined. In addition, variations in viral titer were assayed after treatment of BHK cells with drugs or after transfection with plasmids pCAGM3 and pCAGS3, which encode virus nonstructural proteins μNS and σNS, respectively. Results: NBV-MB infection induced autophagy in host cells; however, the level of induction was dependent on viral replication. Induction of autophagy increased viral replication. By contrast, inhibiting autophagy suppressed NBV replication, albeit not significantly. The NBV-MB nonstructural protein μNS was involved in the induction of autophagy with viral infection. Conclusions: NBV-MB infection triggered autophagy. Also, the NBV nonstructural protein μNS may contribute to augmentation of autophagy upon viral infection. [ABSTRACT FROM AUTHOR]

Carbon isotopes through 6km of fully cored drill holes in 1.7 to 1.5 Ga carbonates of the Mount Isa and McArthur basins, Australia (which host the earliest known eukaryote biomarkers) provide the most comprehensive and best-dated delta 13C stratigraphy yet obtained from such ancient rocks. Both basins reveal remarkably stable temporal delta 13C trends (mean of -0.6% +/- 2% PDB [Peedee belemnite]) and confirm the impression of delta 13C stasis between 2.0 and 1.0 Ga, which, together with other evidence, suggest a prolonged period of stability in crustal dynamics, redox state of surface environments, and planetary climate. This delta 13C stasis is consistent with great stability in the carbon cycle controlled, we suggest, by P limitation of primary productivity. Recent evidence shows that P depletion is a major factor in obligate associations between photosymbionts and host cells. We argue that a billion years of stability in the carbon and nutrient cycles may have been the driving force that propelled prokaryotes toward photosymbiosis and the emergence of the autotrophic eukaryote cell.