The smallest space miners: principles of space biomining

As we aim to expand human presence in space, we need to find viable approaches to achieve independence from terrestrial resources. Space biomining of the Moon, Mars and asteroids has been indicated as one of the promising approaches to achieve in-situ resource utilization by the main space agencies. Structural and expensive metals, essential mineral nutrients, water, oxygen and volatiles could be potentially extracted from extraterrestrial regolith and rocks using microbial-based biotechnologies. The use of bioleaching microorganisms could also be applied to space bioremediation, recycling of waste and to reinforce regenerative life support systems. However, the science around space biomining is still young. Relevant differences between terrestrial and extraterrestrial conditions exist, including the rock types and ores available for mining, and a direct application of established terrestrial biomining techniques may not be a possibility. It is, therefore, necessary to invest in terrestrial and space-based research of specific methods for space applications to learn the effects of space conditions on biomining and bioremediation, expand our knowledge on organotrophic and community-based bioleaching mechanisms, as well as on anaerobic biomining, and investigate the use of synthetic biology to overcome limitations posed by the space environments

The hypoxic transcription factor KlMga2 mediates the response to oxidative stress and influences longevity in the yeast Kluyveromyces lactis

Hypoxia is defined as the decline of oxygen availability, depending on environmental supply and cellular consumption rate. The decrease in O2 results in reduction of available energy in facultative aerobes. The response and/or adaptation to hypoxia and other changing environmental conditions can influence the properties and functions of membranes by modifying lipid composition. In the yeast Kluyveromyces lactis, the KlMga2 gene is a hypoxic regulatory factor for lipid biosynthesis-fatty acids and sterols-and is also involved in glucose signaling, glucose catabolism and is generally important for cellular fitness. In this work we show that, in addition to the above defects, the absence of the KlMGA2 gene caused increased resistance to oxidative stress and extended lifespan of the yeast, associated with increased expression levels of catalase and SOD genes. We propose that KlMga2 might also act as a mediator of the oxidative stress response/adaptation, thus revealing connections among hypoxia, glucose signaling, fatty acid biosynthesis and ROS metabolism in K. lactis

A laboratory for multi-century science

Charles Cockell and colleagues consider what it takes to establish and maintain an experiment that lasts for decades – or even for centuries

Microbial interaction with terrestrial and extraterrestrial rocks on the International Space Station

As space agencies plan to expand human presence in space and to settle on the Moon first and Mars later, developing strategies to achieve this goal in a sustainable way is necessary. These include in situ resource utilization (ISRU) and recovering of materials by waste recycling (1). Microbe based technologies may be pivotal to the success of human space exploration. Potential roles of microorganisms in space include manufacturing, as building blocks of ecosystems, in waste recycling and in biomining (2). Understanding microbial response to space conditions is therefore essential to harness their potential. [...

No Effect of Microgravity and Simulated Mars Gravity on Final Bacterial Cell Concentrations on the International Space Station: Applications to Space Bioproduction

Microorganisms perform countless tasks on Earth and they are expected to be essential for human space exploration. Despite the interest in the responses of bacteria to space conditions, the findings on the effects of microgravity have been contradictory, while the effects of Martian gravity are nearly unknown. We performed the ESA BioRock experiment on the International Space Station to study microbe-mineral interactions in microgravity, simulated Mars gravity and simulated Earth gravity, as well as in ground gravity controls, with three bacterial species: Sphingomonas desiccabilis, Bacillus subtilis, and Cupriavidus metallidurans. To our knowledge, this was the first experiment to study simulated Martian gravity on bacteria using a space platform. Here, we tested the hypothesis that different gravity regimens can influence the final cell concentrations achieved after a multi-week period in space. Despite the different sedimentation rates predicted, we found no significant differences in final cell counts and optical densities between the three gravity regimens on the ISS. This suggests that possible gravityrelated effects on bacterial growth were overcome by the end of the experiment. The results indicate that microbial-supported bioproduction and life support systems can be effectively performed in space (e.g., Mars), as on Earth

Three, two, one yeast fatty acid desaturases: regulation and function

Fatty acid composition of biological membranes functionally adapts to environmental conditions by changing its composition through the activity of lipid biosynthetic enzymes, including the fatty acid desaturases. Three major desaturases are present in yeasts, responsible for the generation of double bonds in position C9-C10, C12-C13 and C15-C16 of the carbon backbone. In this review, we will report data addressed to define the functional role of basidiomycete and ascomycete yeast desaturase enzymes in response to various external signals and the regulation of the expression of their corresponding genes. Many yeast species have the complete set of three desaturases; however, only the Δ9 desaturase seems to be necessary and sufficient to ensure yeast viability. The evolutionary issue of this observation will be discussed

Hypoxia and Glucose Regulate Transcription of the Low-affinity Glucose Transporter Gene RAG1 in Kluyveromyces lactis

Glucose signaling and glycolysis regulates the expression of the low-affinity glucose transporter gene RAG1 in Kluyveromyces lactis. Glucose signaling acts through cascades involving the glucose sensor Rag4 and downstream proteins. A major role is exerted by the casein kinase Rag8 and the repressor proteins Sms1 and KlRgt1. Another pathway involves the chromatin remodeler KlSnf2 and Sck1 and also signals from glycolysis are involved. We have found that transcription of RAG1 is also induced by hypoxia and this induction requires the presence of glucose. Molecular dissection and structural analysis of the RAG1 promoter allowed to identify the region essential for the induction. Transcription analysis of RAG1 in various mutant strains of the glucose regulation allowed to identify Sck1 as the possible element of connection between glucose and oxygen signaling. Dependence of Sck1 expression on hypoxia and binding of Sck1 to the RAG1 promoter has been also investigated. Interestingly, the level of RAG1 transcription, but not the hypoxic induction, depended on the presence of the hypoxic transcription regulator KlMga2. Our results show that the expression of the glucose transporter gene RAG1 is synergistically regulated by high glucose and low oxygen and the glucose regulator Sck1 and the hypoxic regulator KlMga2 might cooperate in this mechanism. NuSA analysis of the promoter in the pertinent physiological conditions and mutant strains, indicates the role of chromatin organization in RAG1 transcriptional regulation

A laboratory for multi-century science

Charles Cockell and colleagues consider what it takes to establish and maintain an experiment that lasts for decades – or even for centuries