The long-term response of microbial communities to the microgravity environment of space is not yet fully understood. Of special interest is the possibility that members of these communities may acquire antibiotic resistance. In this study, Escherichia coli cells were grown under low-shear modeled microgravity (LSMMG) conditions for over 1,000 generations (1000G) using chloramphenicol treatment between cycles to prevent contamination. The results were compared with data from an earlier control study done under identical conditions using steam sterilization between cycles rather than chloramphenicol. The sensitivity of the final 1000G-adapted strain to a variety of antibiotics was determined using Vitek analysis. In addition to resistance to chloramphenicol, the adapted strain acquired resistance to cefalotin, cefuroxime, cefuroxime axetil, cefoxitin, and tetracycline. In fact, the resistance to chloramphenicol and cefalotin persisted for over 110 generations despite the removal of both LSMMG conditions and trace antibiotic exposure. Genome sequencing of the adapted strain revealed 22 major changes, including 3 transposon-mediated rearrangements (TMRs). Two TMRs disrupted coding genes (involved in bacterial adhesion), while the third resulted in the deletion of an entire segment (14,314 bp) of the genome, which includes 14 genes involved with motility and chemotaxis. These results are in stark contrast with data from our earlier control study in which cells grown under the identical conditions without antibiotic exposure never acquired antibiotic resistance. Overall, LSMMG does not appear to alter the antibiotic stress resistance seen in microbial ecosystems not exposed to microgravity. IMPORTANCE Stress factors experienced during space include microgravity, sleep deprivation, radiation, isolation, and microbial contamination, all of which can promote immune suppression (1, 2). Under these conditions, the risk of infection from opportunistic pathogens increases significantly, particularly during long-term missions (3). If infection occurs, it is important that the infectious agent should not be antibiotic resistant. Minimizing the occurrence of antibiotic resistance is, therefore, highly desirable. To facilitate this, it is important to better understand the long-term response of bacteria to the microgravity environment. This study demonstrated that the use of antibiotics as a preventive measure could be counterproductive and would likely result in persistent resistance to that antibiotic. In addition, unintended resistance to other antimicrobials might also occur as well as permanent genome changes that might have other unanticipated and undesirable consequences.

https://journals.asm.org/doi/pdf/10.1128/mBio.02637-18

Evaluation of Acquired Antibiotic Resistance in Escherichia coli Exposed to Long-Term Low-Shear Modeled Microgravity and Background Antibiotic Exposure

Radar Imaging of Binary Near-Earth Asteroid (357439) 2004 BL86

Autonomous control systems onboard planetary rovers and spacecraft benefit from having cognitive capabilities like learning so that they can adapt to unexpected situations in-situ. Q-learning is a form of reinforcement learning and it has been efficient in solving certain class of learning problems. However, embedded systems onboard planetary rovers and spacecraft rarely implement learning algorithms due to the constraints faced in the field, like processing power, chip size, convergence rate and costs due to the need for radiation hardening. These challenges present a compelling need for a portable, low-power, area efficient hardware accelerator to make learning algorithms practical onboard space hardware. This paper presents a FPGA implementation of Q-learning with Artificial Neural Networks (ANN). This method matches the massive parallelism inherent in neural network software with the fine-grain parallelism of an FPGA hardware thereby dramatically reducing processing time. Mars Science Laboratory currently uses Xilinx-Space-grade Virtex FPGA devices for image processing, pyrotechnic operation control and obstacle avoidance. We simulate and program our architecture on a Xilinx Virtex 7 FPGA. The architectural implementation for a single neuron Q-learning and a more complex Multilayer Perception (MLP) Q-learning accelerator has been demonstrated. The results show up to a 43-fold speed up by Virtex 7 FPGAs compared to a conventional Intel i5 2.3 GHz CPU. Finally, we simulate the proposed architecture using the Symphony simulator and compiler from Xilinx, and evaluate the performance and power consumption.

FPGA architecture for deep learning and its application to planetary robotics

Clinostats and Random Positioning Machines (RPMs) are valuable devices for microgravity simulations in order to study fundamental gravity-dependent mechanisms on ground and in preparation for space flights. Both devices have different modes of operation, which have to be carefully considered and comprehensively discussed with respect to their potential impact on the quality of (simulated) microgravity. Here, we used the well-studied oxidative burst reaction of the immune cell (macrophage) model system, in order to compare clinorotation with random positioning. The RPM was used in a clinorotation mode, rotating the sample with 60 rpm around the horizontal axis and in the “random speed mode” (2-10 rpm) with and without random direction, thus, two axes rotating either bi- or unidirectionally. The production of Reactive Oxygen Species (ROS) during oxidative burst of the macrophages was visualized by the luminescence luminol assay. During clinorotation the cells responded with a reduction of the ROS production which is fully in line with earlier studies (clinostat, parabolic flight). In contrast, the exposure to the two random positioning modes showed that the oxidative burst response during RPM-exposure differs significantly from that observed during clinorotation, i.e. a jittering, more variant form of ROS production. We can conclude from our work, that the RPM is not suitable in its real random mode (with and without random direction; 2-10 rpm) to simulate the conditions of microgravity for the chosen system. We recommend that investigators using microgravity simulators should carefully choose the device and mode of operation specifically for their cellular system of interest.

/pdf/validation-of-random-positioning-versus-clinorotation-using-2js39ap9ho.pdf

Validation of Random Positioning Versus Clinorotation Using a Macrophage Model System

Long-duration spaceflight has been shown to negatively affect the lumbopelvic muscles of crewmembers. Through analysis of computed tomography scans of crewmembers on 4- to 6-month missions equipped with the interim resistive exercise device, the structural deterioration of the psoas, quadratus lumborum, and paraspinal muscles was assessed. Computed tomography scans of 16 crewmembers were collected before and after long-duration spaceflight. The volume and attenuation of lumbar musculature at the L2 vertebral level were measured. Percent changes in the lumbopelvic muscle volume and attenuation (indicative of myosteatosis, or intermuscular fat infiltration) following spaceflight were calculated. Due to historical studies demonstrating only decreases in the muscles assessed, a one-sample t test was performed to determine if these decreases persist in more recent flight conditions. Crewmembers on interim resistive exercise device-equipped missions experienced an average 9.5% (2.0% SE) decrease in volume and 6.0% (1.5% SE) decrease in attenuation in the quadratus lumborum muscles and an average 5.3% (1.0% SE) decrease in volume and 5.3% (1.6% SE) decrease in attenuation in the paraspinal muscles. Crewmembers experienced no significant changes in psoas muscle volume or attenuation. No significant changes in intermuscular adipose tissue volume or attenuation were found in any muscles. Long-duration spaceflight was associated with preservation of psoas muscle volume and attenuation and significant decreases in quadratus lumborum and paraspinal muscle volume and attenuation.

/pdf/lumbopelvic-muscle-changes-following-long-duration-2l09j6sf9f.pdf

Lumbopelvic Muscle Changes Following Long-Duration Spaceflight.

Wheeled planetary rovers such as the Mars Exploration Rovers (MERs) and Mars Science Laboratory (MSL) have provided unprecedented, detailed images of the Mars surface. However, these rovers are large and are of high-cost as they need to carry sophisticated instruments and science laboratories. We propose the development of low-cost planetary rovers that are the size and shape of cantaloupes and that can be deployed from a larger rover. The rover named SphereX is 2 kg in mass, is spherical, holonomic and contains a hopping mechanism to jump over rugged terrain. A small low-cost rover complements a larger rover, particularly to traverse rugged terrain or roll down a canyon, cliff or crater to obtain images and science data. While it may be a one-way journey for these small robots, they could be used tactically to obtain high-reward science data. The robot is equipped with a pair of stereo cameras to perform visual navigation and has room for a science payload. In this paper, we analyze the design and development of a laboratory prototype. The results show a promising pathway towards development of a field system.

Spherical planetary robot for rugged terrain traversal

We advocate a low-cost strategy for long-duration research into the ‘milligravity’ environment of asteroids, comets and small moons, where surface gravity is a vector field typically less than 1/1000 the gravity of Earth Unlike the microgravity environment of space, there is a directionality that gives rise, over time, to strangely familiar geologic textures and landforms In addition to advancing planetary science, and furthering technologies for hazardous asteroid mitigation and in situ resource utilization, simplified access to long-duration milligravity offers significant potential for advancing human spaceflight, biomedicine and manufacturing We show that a commodity 3U (10 × 10 × 34 cm3) cubesat containing a laboratory of loose materials can be spun to 1 rpm = 2π/60 s−1 on its long axis, creating a centrifugal force equivalent to the surface gravity of a kilometer-sized asteroid We describe the first flight demonstration, where small meteorite fragments will pile up to create a patch of real regolith under realistic asteroid conditions, paving the way for subsequent missions where landing and mobility technology can be flight-proven in the operational environment, in low-Earth orbit The 3U design can be adapted for use onboard the International Space Station to allow for variable gravity experiments under ambient temperature and pressure for a broader range of experiments

/pdf/a-cubesat-centrifuge-for-long-duration-milligravity-research-4yxks7ja3y.pdf

A cubesat centrifuge for long duration milligravity research.

Asteroid Origins Satellite (AOSAT) I: An On-orbit Centrifuge Science Laboratory

We advocate a low-cost strategy for long-duration research into the 'milligravity' environment of asteroids, comets and small moons, where surface gravity is a vector field typically less than 1/1000 the gravity of Earth. Unlike the microgravity environment of space, there is a directionality that gives rise, over time, to strangely familiar geologic textures and landforms. In addition to advancing planetary science, and furthering technologies for hazardous asteroid mitigation and in-situ resource utilization, simplified access to long-duration milligravity offers significant potential for advancing human spaceflight, biomedicine and manufacturing. We show that a commodity 3U ($10\times10\times34$ cm$^3$) cubesat containing a laboratory of loose materials can be spun to 1 rpm = $2\pi/60$ s$^{-1}$ on its long axis, creating a centrifugal force equivalent to the surface gravity of a kilometer-sized asteroid. We describe the first flight demonstration, where small meteorite fragments will pile up to create a patch of real regolith under realistic asteroid conditions, paving the way for subsequent missions where landing and mobility technology can be flight-proven in the operational environment, in Low-Earth Orbit (LEO). The 3U design can be adapted for use onboard the International Space Station (ISS) to allow for variable gravity experiments under ambient temperature and pressure for a broader range of experiments.

A Cubesat Centrifuge for Long Duration Milligravity Research

A correction to this article has been published and is linked from the HTML version of this article.

/pdf/erratum-a-cubesat-centrifuge-for-long-duration-milligravity-41c08hj20q.pdf

Laksh Raura

Papers

Spherical planetary robot for rugged terrain traversal

A cubesat centrifuge for long duration milligravity research.

Asteroid Origins Satellite (AOSAT) I: An On-orbit Centrifuge Science Laboratory

A Cubesat Centrifuge for Long Duration Milligravity Research

Erratum: A cubesat centrifuge for long duration milligravity research.