Search for: All records

Abstract The numerous ephemeral glacial meltwater streams that flow during the summer in the McMurdo Dry Valleys of South Victoria Land, Antarctica, provide habitats for microbial mats. One of the common mat types is composed of Chlorophyta (colloquially known as a ‘green mat’ due to its colour). While the presence of these mats is regularly monitored, their taxonomic makeup is still under investigation. Using 18S rRNA gene sequencing, the composition of the chlorophyte-dense mats from between rocks and in the main channel from several streams across two valleys was examined. Samples were maintained in native stream water, and select samples from representative locations were transferred to Bristol Medium. The appearance of other eukaryotic species - diatoms and tardigrades - in these green mats completed this integrated study. The results show that the relative abundance of Chlorophyta was significantly increased with the introduction of inorganic nitrogen from Bristol Medium. Chlorophyte taxa in theHazeniaandPleurastrumgenera dominated the samples across both sample types (rock or exposed) and treatments (Antarctic water or Bristol Medium). Furthermore, a reduction in overall sample diversity was observed in samples in Bristol Medium, suggesting preferential nitrogen utilization by these chlorophytes. 

Abstract Viruses are the most numerically abundant biological entities on Earth. As ubiquitous replicators of molecular information and agents of community change, viruses have potent effects on the life on Earth, and may play a critical role in human spaceflight, for life-detection missions to other planetary bodies and planetary protection. However, major knowledge gaps constrain our understanding of the Earth's virosphere: (1) the role viruses play in biogeochemical cycles, (2) the origin(s) of viruses and (3) the involvement of viruses in the evolution, distribution and persistence of life. As viruses are the only replicators that span all known types of nucleic acids, an expanded experimental and theoretical toolbox built for Earth's viruses will be pivotal for detecting and understanding life on Earth and beyond. Only by filling in these knowledge and technical gaps we will obtain an inclusive assessment of how to distinguish and detect life on other planetary surfaces. Meanwhile, space exploration requires life-support systems for the needs of humans, plants and their microbial inhabitants. Viral effects on microbes and plants are essential for Earth's biosphere and human health, but virus–host interactions in spaceflight are poorly understood. Viral relationships with their hosts respond to environmental changes in complex ways which are difficult to predict by extrapolating from Earth-based proxies. These relationships should be studied in space to fully understand how spaceflight will modulate viral impacts on human health and life-support systems, including microbiomes. In this review, we address key questions that must be examined to incorporate viruses into Earth system models, life-support systems and life detection. Tackling these questions will benefit our efforts to develop planetary protection protocols and further our understanding of viruses in astrobiology. 

Including a multifunctional, bioregenerative algal photobioreactor for simultaneous air revitalization and thermal control may aid in carbon loop closure for long-duration surface habitats. However, using water-based algal media as a cabin heat sink may expose the contained culture to a dynamic, low temperature environment. Including psychrotolerant microalgae, native to these temperature regimes, in the photobioreactor may contribute to system stability. This paper assesses the impact of a cycled temperature environment, reflective of spacecraft thermal loops, to the oxygen provision capability of temperate Chlorella vulgaris and eurythermic Antarctic Chlorophyta. The tested 28-min temperature cycles reflected the internal thermal control loops of the International Space Station ( C . vulgaris , 9–27°C; Chlorophyta-Ant, 4–14°C) and included a constant temperature control (10°C). Both sample types of the cycled temperature condition concluded with increased oxygen production rates ( C . vulgaris ; initial: 0.013 mgO 2 L –1 , final: 3.15 mgO 2 L –1 and Chlorophyta-Ant; initial: 0.653 mgO 2 L –1 , final: 1.03 mgO 2 L –1 ) and culture growth, suggesting environmental acclimation. Antarctic sample conditions exhibited increases or sustainment of oxygen production rates normalized by biomass dry weight, while both C . vulgaris sample conditions decreased oxygen production per biomass. However, even with the temperature-induced reduction, cycled temperature C . vulgaris had a significantly higher normalized oxygen production rate than Antarctic Chlorophyta. Chlorophyll fluorometry measurements showed that the cycled temperature conditions did not overly stress both sample types (F V /F M : 0.6–0.75), but the Antarctic Chlorophyta sample had significantly higher fluorometry readings than its C . vulgaris counterpart ( F = 6.26, P < 0.05). The steady state C . vulgaris condition had significantly lower fluorometry readings than all other conditions (F V /F M : 0.34), suggesting a stressed culture. This study compares the results to similar experiments conducted in steady state or diurnally cycled temperature conditions. Recommendations for surface system implementation are based off the presented results. The preliminary findings imply that both C . vulgaris and Antarctic Chlorophyta can withstand the dynamic temperature environment reflective of a thermal control loop and these data can be used for future design models.