The two strains that have been described as X. fastidiosa subsp. sandyi-like, CO33 and CFBP8356, both clustered within X. fastidiosa subsp. fastidiosa, not with the other potential X. fastidiosa subsp. sandyi strains Ann1 and RAAR8_XF70, supporting previous work showing that there is not a strong distinction between X. fastidiosa subsp. sandyi and X. fastidiosa subsp. fastidiosa . The core genome tree also has very low bootstrap support for X. fastidiosa subsp. pauca, which is the most diverse and oldest of the three main subspecies that could be potentially due to conflicting histories between horizontal and vertical descent or, alternatively, reflect that this group is simply not well supported as one subspecies . In terms of the poor resolution in the OQDS clade, an analysis has recently been conducted to increase resolution within these strains . Given the diversity of X. fastidiosa subsp. pauca, the Hib4 strain, the outgroup of the subspecies, could be a potentially interesting strain in terms of both function and evolutionary history . It is difficult to know which phylogenies are more accurate than others; however, we assume that the core genome is the most accurate at depicting the descent of this bacterial species,danish trolley and the topology should be robust to even high levels of recombination . While the non-recombinant core genome might reduce some issues with horizontal gene transfer, the lack of resolution because of too many identical sequences makes it difficult to use.

While more data are not intrinsically better, there are known issues with the MLST genes used for X. fastidiosa phylogenetics, and having a larger set of unbiased homologous regions should be able to lend data to support nodes that are difficult to differentiate using the smaller MLST data set . Using the core genome phylogeny, the most likely ancestral host was inferred from the phylogeny. These results show us that the phylogenetic history of X. fastidiosa is significantly correlated with the agricultural plant host from which the strains were isolated. While the core genome phylogeny depicts mainly vertical descent within this bacterial species, the pan-genome phylogeny likely combines vertical descent with horizontal gene transfer. This is due to the pan-genome’s inclusion of the accessory genome, which are genes not shared by all members of the group . Based on this, we speculate that there is both adaptation and convergence depicted in these results. Potentially, both convergent horizontal descent via gene gain and loss, as well as vertical descent in the core, leads to our modern distribution of traits. While the ancestral state reconstruction did not show a classic host-parasite story of cospeciating or phylogenetically conserved host specificity, the phylogeny and gene presence/absence are predictive of the hosts from which the strains were isolated, and thus hypothetically, host specificity as well. While the four ancestral state reconstructions do not show identical histories, they all infer a high likelihood of ancestral hosts at many key branch points of the three subspecies. The pan- and core genome reconstructions predict the genus Vaccinium as the most likely ancestral host of the X. fastidiosa subsp. multiplex, which supports the overall reliability of the reconstruction, as blueberry, like X. fastidiosa subsp. multiplex, is native to eastern North America . X. fastidiosa subsp. pauca, X. fastidiosa subsp. multiplex, and X. fastidiosa subsp. fastidiosa all exhibit host shifts from another genus to Prunus, suggesting potential for increased vulnerability in this genus to infection from varied alternative hosts.

All four reconstructions also support the genus Coffea as the most likely ancestor of the introduced X. fastidiosa subsp. fastidiosastrains from Central American to California. This supports a previous hypothesis made by Nunney et al. wherein coffee plants that were imported from Central America to southern California in the mid-1800s might have brought X. fastidiosa subsp. fastidiosa along with them. Given the potential role of imported Coffea in devastating global outbreaks of disease caused by X. fastidiosa , it should be much more carefully monitored or restricted in global trade. Given the current policy emphasis on eradication and trade restrictions, it is vital to identify genera such as Coffea that are especially relevant to global outbreaks and that should be monitored carefully. The relationship between X. fastidiosa and Coffea should be further explored as a model host to aid our understanding of the molecular mechanisms of this complex interaction. A potential alternative hypothesis for these nodes could also be that Coffea and Vaccinium are permissive hosts. From a parsimony perspective, they could be akin to “universal hosts” so that it takes very little change for X. fastidiosa strains to switch to Coffea or Vaccinium from other infected plants. This could be investigated by further interrogating the genes shown to be uniquely absent in Coffea-infecting strains. Phylogenetically, this would reflect deep homology in which the underlying genetic framework of the pathogens makes it easy to shift from other plant hosts to Coffea or Vaccinium . The two plant genera with genes significantly correlated with them, Vitis and Coffea, had 179 and 20 whole-genome sequences from diverse sampling regions, respectively. The larger clades of Proteales, Asterid, and Rosid were also used to look for convergent gene presence and absence, and again, the two groups with the majority of samples, Asterid and Rosid , had genes correlated with them, while Proteales did not.

The genes found to be correlated with these host groupings had varied functions. Unfortunately, out of these 23 genes, 20 are hypothetical proteins; the ones with known functions could have very interesting implications for host range. fitB_1 has been known to be involved in in-host migration and metal binding; similar genes are also frequently gained and lost in other Xanthomonadaceae and are hypothesized to affect both gene regulation and resistance mechanisms . vhbT is an interbacterial effector protein, facilitating bacterial conjugation, another process with potential for large genomic and functional changes . Another significant gene contains a helix-turn-helix region, a DNA binding domain that has been found to control metal resistance bacteria generally and biofilm growth in X. fastidiosa specifically . These genes should be explored further through fitness tests with the presence and absence of these nonessential accessory genes in multiple-host environments to further evaluate if their presence and absence is adaptive or due to drift. Future research pertaining to host range should focus on both convergent gene gain and loss, as well as the adaptive vertically descended genetics underlying host range. As both genomic assays have identified the pan-genome to be linked to host association, it would be beneficial to our understanding of host specificity to pursue this further. This study has identified a group of candidate genes associated with particular hosts, and they can be tested in the lab to determine if they are significantly linked to fitness in their particular hosts. The study has also identified Coffea as an especially relevant host in global plant trade in terms of spreading infection across borders and oceans. Using these data, we can start identifying patterns of likely host shifts that can help make decisions on when eradication and quarantine are necessary based on the historical likelihood of host shifts. However, we should also carry out further whole-genome sequencing of strains outside the classic agricultural settings. To truly understand a biological system, we not only need to understand the relevant biological components but also how they interact both inside and outside agricultural landscapes.As commercial aerospace companies advance toward manned spaceflight,vertical aeroponic tower garden they must overcome many hurdles – not only technical, but also human. One of the greatest human challenges they face is food. Providing astronauts with nourishing and appetizing food has been a challenge ever since human spaceflight began in 1961. At that time, little was known about how eating would work in a weightless environment . Would astronauts be able to swallow? Would they be able to digest? How difficult would it be to deal with crumbs? These unknowns led state-run organizations, such as the United States’ National Aeronautics and Space Administration and the former Soviet Union’s various groups to provide early astronauts and cosmonauts with pureed and cubed space foods. Yet although these foods made for fun gifts on Earth, they were not always so well received in outer space, and space food often returned to Earth uneaten . Astronauts’ inadequate intake was problematic, not only because sending uneaten food to and from outer space was a waste of money, but also because it put astronauts at risk for nutrient deficiencies. Nutrient deficiencies have been shown to lead to impairments in mood, social skills, concentration, and ability to withstand stress . Consequently, insufficient food intake posed a threat to astronauts’ health and the success of space missions that depended upon their emotional, social, and cognitive abilities to respond in life-and-death situations.To overcome these difficulties with food intake, the United States government invested substantial resources into pioneering new food technologies that could pave the way to more palatable space foods .

First through the U.S. Army and the Air Force, and now through the NASA Space Food Laboratory, the United States developed numerous novel food technologies . These new technologies were shared with American food manufacturers, resulting in many of the foods seen on grocery store shelves today. Portable, long shelf-life foods such as granola bars, heat-processed juice pouches, freeze-dried foods, and fruit bars are just a few of many types of foods that are commercially available, yet that can be traced back to technologies whose development was funded by the U.S. government . As a result of NASA, Army, and Air Force food endeavors, one can now purchase numerous foods from the supermarket that would work in outer space. This is good news for commercial aerospace companies SpaceX and Boeing, who are currently developing Crew1 Transportation Vehicles under NASA contract. Starting in 2017, these Crew Transportation Vehicles could be used to transport NASA astronauts to and from the International Space Station . In the years after that, these vehicles could also be used to transport civilians to and from outer space, either to the ISS or to other, yet to be determined, locations. Consequently, these commercial aerospace companies may want to provide food in their Crew Transportation Vehicles that could withstand flights to and from the ISS. This food would not be eaten on the ISS, but would be eaten on return trips after ISS stays, which are traditionally six months in duration. Accordingly, the food should have a minimum shelf life of seven months.To be usable on these flights, the food must be shelf stable and ready-to-eat, as refrigerators and food heaters would not be available. Additionally, the food should provide four days’ worth of nutrition, as astronauts could be in the Crew Transportation Vehicle for up to this length of time. 2 The food must also be able to withstand the extreme conditions of spaceflight. As a result of the commercialization of NASA, Army, and Air Force technologies, numerous commercially available foods should now be able to meet these requirements; but can these foods keep astronauts nourished, satisfied with their diet, and both psychologically and physically healthy?The purpose of this study was to evaluate the consequences of having an astronaut analog sample eat a diet of commercial, ready-to-eat food for four days , as compared to eating as normal for four days . In particular, the specific aims of this study were to investigate the impact of the experimental condition on nutrient intake, food satisfaction, psychological health, and physical health. Although the study was health psychology-focused and therefore had the investigation of psychological health as its most critical aim, nutrient intake and food satisfaction greatly determine subsequent psychological health, and these two aspects will therefore be discussed first. Astronauts require similar calories and nutrients in outer space as they do on ground . At the most basic level, astronauts require adequate nutrients from their food. Yet what is “adequate” for an astronaut? When human spaceflight first began, it was not clear what sort of calories and nutrients astronauts would require in microgravity. During Project Mercury , which was the first NASA mission to send food to outer space, astronauts were provided with 2,500 calories a day . This allotment was based on the assumption that astronauts would require fewer calories because floating in microgravity would require less use of their muscles .