While it has been shown that astronauts suffer immune disorders after spaceflight, the underlying causes are still poorly understood and there are many variables to consider when investigating the immune system in a complex environment. Additionally, there is growing evidence that suggests that not only is the immune system being altered, but the pathogens that infect the host are significantly influenced by spaceflight and ground-based spaceflight conditions. In this study, we demonstrate that Serratia marcescens (strain Db11) was significantly more lethal to Drosophila melanogaster after growth on the International Space Station than ground-based controls, but the increased virulence phenotype of S. marcescens did not persist after the bacterial cultures were passaged on the ground. Increased virulence was also observed in bacteria that were grown in simulated microgravity conditions on the ground using the rotating wall vessel. Increased virulence of the space-flown bacteria was similar in magnitude between wild-type flies and those that were mutants for the well-characterized immune pathways Imd and Toll, suggesting that changes to the host immune system after infection are likely not a major factor contributing towards increased susceptibility of ground-reared flies infected with space-flown bacteria. Characterization of the bacteria shows that at later timepoints spaceflight bacteria grew at a greater rate than ground controls in vitro, and in the host. These results suggest complex physiological changes occurring in pathogenic bacteria in space environments, and there may be novel mechanisms mediating these physiological effects that need to be characterized.

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Having an effective immune system can be very costly, sometimes at the expense of other important life history traits, including reproduction. This tradeoff can be exaggerated in males of species that have costly sexual signaling, where conditiondependent components of the signaling system reflect the health status of the bearer. It is therefore vital for a male to be able to adequately balance the costs of activating the immune system successfully while also expressing high quality sexual signals. We examined males of the brush-legged wolf spider Schizocosa ocreata to see whether static condition-dependent components of sexual signaling in adult males would be indicative of health status (immune stress response), and whether female preference for these traits could be influenced by infection. After experimental ingestion of a bacterial pathogen (Pseudomonas aeruginosa), symmetry of male foreleg tuft (a secondary sexual trait) was found to predict the intensity of the subsequent infection, such that males with more asymmetrical tufts had a higher level of bacteria found in the hemolymph when tested after ingestion. Females were equally likely to mate with both infected and uninfected males in live mating trials, but were found to have bacteria both in their hemolymph and on their body surface as a consequence of mating with infected males. Males that engaged in courtship had significantly lower encapsulation response than naïve males, but among those males that courted, larger tuft size indicated a higher encapsulation response even after energetically costly courtship. These results indicate that females may be able to use static sexual signaling traits to examine a male's overall health, but do not appear to discriminate against males who are actively

Summary With the development of transcriptomic technologies, we are able to quantify precise changes in gene expression profiles from astronauts and other organisms exposed to spaceflight. Members of NASA GeneLab and GeneLab-associated analysis working groups (AWGs) have developed a consensus pipeline for analyzing short-read RNA-sequencing data from spaceflight-associated experiments. The pipeline includes quality control, read trimming, mapping, and gene quantification steps, culminating in the detection of differentially expressed genes. This data analysis pipeline and the results of its execution using data submitted to GeneLab are now all publicly available through the GeneLab database. We present here the full details and rationale for the construction of this pipeline in order to promote transparency, reproducibility, and reusability of pipeline data; to provide a template for data processing of future spaceflight-relevant datasets; and to encourage cross-analysis of data from other databases with the data available in GeneLab.