Browsing by Author "Khodadad, Christina"

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Biofilm Resistant Coatings for Space Applications
(48th International Conference on Environmental Systems, 2018-07-08) Li, Wenyan; Hummerick, Mary; Khodadad, Christina; Buhrow, Jerry; Spencer, Lashelle; Coutts, Janelle; Roberson, Luke; Tuteja, Anish; Mehta, Geeta; Boban, Mathew; Barden, Michael
Bacterial biofilms are an important and often problematic aspect of life on earth and in space. Microbial contamination onboard the International Space Station (ISS) continues to pose mission risks, both to crew health and hardware reliability. In order to optimize the design of the future space exploration vehicle for long term missions, new technologies are needed to control the habitat’s microbial environment over multiple years. Among the emerging technologies for combating biofilm, new surface coatings show promise for preventing biofilm formation. This approach aims to interrupt the critical initial step of biofilm formation (cell attachment) through surface modification. When successfully developed, biofilm resistant coatings can eliminate/reduce the need for disinfectants, and avoid the development of “superbugs,” thus offering distinctive advantages for biofilm prevention during long term missions. Initial results at KSC showed that omniphobic coatings are promising candidates as biofilm resistant materials. Parabolic flight experiments also verified their physical properties under microgravity.
Hollow Fiber Membrane Bioreactor Systems for Wastewater Processing: Effects of Environmental Stresses Including Dormancy Cycling and Antibiotic Dosing
(46th International Conference on Environmental Systems, 2016-07-10) Coutts, Janelle; Hummerick, Mary; Lunn, Griffin M.; Larson, Brian; Spencer, Lashelle; Kosiba, Michael; Khodadad, Christina; Catechis, John
Hollow fiber membrane bioreactors (HFMBs) have been studied for a number of years as an alternate approach for treating wastewater streams during space exploration. While the technology provides a promising pre-treatment for lowering organic carbon and nitrogen content without the need for harsh stabilization chemicals, several challenges must be addressed before adoption of the technology in future missions. One challenge is the transportation of bioreactors containing intact, active biofilms as a means for rapid start-up on the International Space Station or beyond. Similarly, there could be a need for placing these biological systems into a dormant state for extended periods when the system is not in use, along with the ability for rapid restart. Previous studies indicated that there was little influence of storage condition (4 or 25ºC, with or without bulk fluid) on recovery of bioreactors with immature biofilms (48 days old), but that an extensive recovery time was required (20+ days). Bioreactors with fully established biofilms (13 months) were able to recover from a 7-month dormancy within 4 days (~1 residence). Further dormancy and recovery testing is presented here that examines the role of biofilm age on recovery requirements, repeated dormancy cycle capabilities, and effects of long-duration dormancy cycles (8-9 months) on HFMB systems. Another challenge that must be addressed is the possibility of antibiotics entering the wastewater stream. Currently, for most laboratory tests of biological water processors, donors providing urine may not contribute to the study when taking antibiotics because the effects on the system are yet uncharacterized. A simulated urinary tract infection event, where an opportunistic, pathogenic organism, E. coli, was introduced to the HFMBs followed by dosing with an antibiotic, ciprofloxacin, was completed to study the effect of the antibiotic on reactor performance and to also examine the development of antibiotic-resistant communities within the system.
Investigation into Simulated Microgravity Techniques Used to Study Biofilm Growth
(51st International Conference on Environmental Systems, 2022-07-10) Diaz, Angie; Li, Wenyan; Irwin, Tesia; O'Rourke, Aubrie; Calle, Luz; Hummerick, Mary; Khodadad, Christina; Gleeson, Jonathan; Callahan, Michael
Bacterial growth in liquid media in microgravity conditions is not well understood. Trends such as a shortened lag phase, longer log phase, slower growth rate, and a higher final population concentration have been noted but the underlying cause remains unclear. At the single cell level, it is predicted that bacteria are less gravity-sensitive than larger species. The effects on their immediate environment, including the lack of cell settlement and slower mass transfer of nutrients due to lack of density driven convection, could help explain the trends. Ground-based spaceflight analogs, or simulated microgravity devices, are often employed to achieve different attributes of weightlessness to study effects on bacterial growth. Though these technologies could isolate gravity s role in various biological processes, they cannot replicate all its effects and underlying mechanisms. Hence, interpretation of results could be misleading, even if similar to spaceflight. In this study two common simulated microgravity devices were investigated to determine whether they could simulate relevant microgravity conditions for bacterial growth. A bioreactor, the high aspect ratio vessel (HARV), was used with dyes of different density mounted on a random positioning machine (RP machine) or a rotating wall vessel (RWV). The RP machine displayed higher mixing rates than the RWV. The RWV was further tested at different rotations per minute (RPM). The range to minimize effects of density driven convection (low speeds) or centrifugal forces (high speeds) was between a range of 15-20 RPM. These results will help inform the selection of simulated microgravity device as well as interpretation of subsequent biofilm growth results.
Survey of Microbial Community in Bioreactors Used for Bioregenerative Water Purification
(2023 International Conference on Environmental Systems, 2023-07-16) Saetta, Daniella; Bullard, Talon; Smith, Alexandra; Yeh, Daniel; Fischer, Jason; Dixit, Anirudha; Spern, Cory; Khodadad, Christina; Roberson, Luke
Bioregenerative water purification systems are promising ECLSS technologies because they allow for complete recovery of water and nutrients for sustainable planetary base operations. These systems use a consortium of microbes to treat complex waste streams that have generally been ignored thus far, such as fecal and food waste. However, the microbial community structure of the bioreactors is largely unknown. The main goal of this paper was to survey the microbial community of four distinct bioreactors to provide a deeper understanding of the bioreactors in terms of treatment and operational hazards. The survey encompassed four types of aerobic and anaerobic bioreactors with real and ersatz influents, giving a wide picture of the microbial community across a wide range of conditions. We used shotgun metagenomics to provide a comprehensive analysis of the community constituents, which included bacteria, viruses, archaea, and eucarya. The study sampled two identical anaerobic membrane bioreactors (one with canine fecal waste influent and one with an ersatz influent), a suspended aerobic membrane bioreactor (with real human urine as its influent), and a photo−membrane bioreactor (with anaerobic membrane bioreactor effluent as its influent). This is the first study of its kind to study the microbiome of bioreactors designed for early planetary wastewater treatment. Results show a high level of diversity among the samples, with higher DNA densities in the samples from the reactors with real fecal and urine influents. Overall, this conference paper will detail how the bioreactor conditions affected the microbial community structure and how the community structure influences the wastewater treatment process.